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Article

Valorization of Bioactive Compounds Extracted from Brewer’s Spent Grain (BSG) for Sustainable Food Waste Recycling

by
Hao-Yu Ivory Chu
,
Taghi Miri
* and
Helen Onyeaka
School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
*
Author to whom correspondence should be addressed.
Sustainability 2025, 17(6), 2477; https://doi.org/10.3390/su17062477
Submission received: 7 January 2025 / Revised: 6 March 2025 / Accepted: 9 March 2025 / Published: 12 March 2025
(This article belongs to the Section Sustainable Food)
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Abstract

:
In parallel with the worldwide issues of malnutrition and food waste, society at large focuses on the advantages of ‘recycling’ food waste. Brewer’s spent grain (BSG), a primary byproduct of the brewing industry, is produced in large quantities in many regions of the world, leading to environmental issues. The present study aimed at valorizing BSG through bioactive compound extraction using more traditional approaches, including Soxhlet extraction, recrystallization, and salting-out adsorption for proteins and lactic purification. The extraction rate of total dietary fiber (TDF) was 93.3%. FTIR analysis showed specific structural vibrations of fiber with C-O and C-O-C attachments in hemicellulose, C-H bends in lignin, and various bending patterns in tannins and fatty acid esters. Hemicellulose (8245.2 mg/L), lignin (10,432.4 mg/L), and cellulose (13,245.4 mg/L) were extracted with rates of 54.9%, 69.5%, and 88.3%, respectively. These bioactive compounds extracted from BSG could be utilized in food and nutraceutical products based on their purity. The analysis of extracted bioactive components confirmed the presence of arachidic acid (C20:0), oleic acid (C18:1), linoleic acid (C18:2), myristic acid (C14:0), pentacyclic acid (C30:0), palmitic acid (C16:0), margaric acid (C17:0), gallic acid, catechol, ellagic acid, acetyl sialic acid, benzoic acid, and vanillin. These findings highlight the valorization potential of BSG, a previously regarded waste material, as a source of active biocomponents. This is consistent with the principles of the circular economy by reducing waste in the environment and supporting tangible sustainability in food systems. The efforts made in the current study in utilizing BSG are part of the fast-growing area of food waste recycling and provide a way to avoid waste and create added value.

1. Introduction

Brewer’s spent grain (BSG) generated from the brewing process has attracted the focus of many researchers due to its potential to address the growing issue of waste resulting from beer production [1,2,3]. BSG, obtained after the lautering process, is the non-soluble portion of fermented grains and significantly contributes to global waste issues. Nearly 30 million metric tons of BSG are produced annually, making it one of the top three industrial waste byproducts [4]. Recovering value from BSG enables breweries to adapt to social development and environmental sustainability, converting an otherwise discarded byproduct into a source of profit. The externally extracted bioactive components from BSG have provided breweries and other connected sustainable industries with additional revenue opportunities [5].
BSG is routinely used as cheap animal feed since it contains high amounts of fiber (30–50% w/w) and protein (19–30% w/w) [6,7]. The fiber from BSG has potential applications in the production of baked goods, snack products, and food fortification due to the increasing demand for high-fiber food products [8,9].
Nevertheless, these nutrients are of high quality and suitable for human consumption, sparking interest in the extraction of bioactive compounds from BSG for use in food and health products. Many of the bioactive compounds present in BSG, such as phenolic acids, dietary fibers, and proteins, possess functional properties that can be utilized for value-added applications in the food and nutraceutical industries [10,11]. Likewise, dietary fiber has gained significant attention due to its usefulness not only in functional foods but also in food packaging and drug delivery, broadening its industrial applications.
In addition, some of the other key bioactive compounds extracted include palmitic acid, oleic acid, vanillin, ellagic acid, and gallic acid. These compounds are important because they exhibit antioxidative, anti-inflammatory, and potentially anticancer properties, making them valuable for food and health applications [12,13]. For instance, the presence of palmitic acid and oleic acid in significant quantities present opportunities for natural additive industries. Palmitic acid is a saturated fatty acid widely used in health products and is potentially applicable in products focused on nutritional enhancement.
Oleic acid is also highly valued for its skin-related benefits and is incorporated into cosmetic products to prevent dry skin and reduce inflammation [14]. Antioxidant-rich phenolic compounds mitigate oxidative stress, a primary factor associated with skin aging and other inflammatory conditions [15,16]. For example, ellagic acid is known for its anti-aging effects in skincare products [17], while catechol plays a role in soothing formulations due to its anti-inflammatory properties [18].
This investigation aligns with the principles of the circular economy by converting waste into valuable resources while reducing environmental effects. According to the United Nations Sustainable Development Goal 12 (SDG 12), which focuses on “Responsible Consumption and Production”, the optimal use of industrial byproducts like BSG is an important step toward sustainable resource management. By repurposing BSG into useful food ingredients, dietary supplements, and bio-based materials, this study helps to reduce waste, the demand for virgin ingredients, and landfill buildup.
Furthermore, based on an investigation by the United Nations, cyclical reuse of food waste has been shown to effectively reduce carbon emissions and reliance on nonrenewable resources. When compared to traditional landfill disposal and incineration procedures, recycling BSG as a source of bioactive chemicals can dramatically reduce methane emissions and land usage requirement. Furthermore, this circular economy model can help save water resources because reusing BSG minimizes the requirement for farming and processing new raw materials, lowering the overall water footprint.
The procedure for isolating bioactive elements from BSG provides specific pretreatments for actual targets. Most of the phenolic substances found in cells are contained in cytosolic vesicles; therefore, an active extraction solvent cannot just be added without the treatment of either alkaline hydrolysis or some other treatment of the polymer [19]. Acid pretreatment, which involves the use of acids to reduce cellulosic structures for further processes, is widely used in protein extraction methods, especially in bioethanol production from plant biomass [20,21,22]. Bioactive components obtained from or created using BSG exhibit a wide range of uses. For example, they are used as natural preservatives in food, and in cosmetics and dietary supplements, they are incorporated into products that claim to display certain benefits [23,24]. Of these compounds, phenolic acids and complex fatty acids are distinguished by antioxidant and therapeutic effects due to their ability to enhance oxidative stress by means of resonance stabilization and interaction with transcription factors. These antioxidants may lower the prevalence of chronic diseases and promote health [25]. The phenolic composition of BSG, which contains compounds such as hydroxycinnamic acids, is determined by the type of barley, malt, and brewing process in which ferulic acid, p-coumaric acid, caffeic acid, and syringic acid can be found [26]. Usually, these compounds are attached to lignin through ether and ester linkages, making these compounds difficult to extract; however, once extracted, they can generate significant revenue [27,28].
In this study, a simple and effective method based on the solvent extraction and Soxhlet extraction techniques to extract and characterize fiber bioactive compounds from BSG was employed. This investigation directly contributes to sustainability by extracting bioactive compounds from BSG, converting a major industrial waste into valuable materials and lowering the demand for new raw resources.
The underlying mechanism was supported by the existing literature on the utilization of BSG’s rich bioactive profile. This study focused on extracting and utilizing BSG rich in active compounds to enhance the value of otherwise discarded food raw materials, thereby promoting environmentally friendly practices in food processing. This approach was consistent with the principles of the circular economy, in which waste was treated as a resource, promoting sustainable development by reducing waste disposal and minimizing the environmental impact of industries.
The objective of this research was to assess the feasibility of utilizing BSG for biorefining processes, serving as a bioactive compound source for food and nutraceutical applications. By valorizing BSG through bioactive compound extraction using traditional approaches—such as Soxhlet extraction, recrystallization, and salting-out adsorption for fiber, phenolic, and antioxidant purification—this study contributes to enhancing food system sustainability by reducing existing waste materials. Figure 1 presents a graphical abstract of this study.

2. Materials and Method

2.1. Material and Chemicals

Brewer’s spent grain (BSG) was kindly supplied by ATTICBREW CO, Birmingham, UK. Fresh BSG, which initially contained approximately 80% moisture, was dried at 60 °C overnight to yield dried BSG. The dried BSG was then ground using a grinder until its moisture content reached 6% and was stored at 4 °C in an airtight container.
The Soxhlet extraction and recrystallization process were performed to extract phenolic compounds and antioxidants. The sample used for this process weighed 5 g.
The chemicals used for extraction included petroleum ether, n-hexane, ethyl acetate, sodium chloride, formic acid, potassium dihydrogen phosphate, and magnesium sulfate. These chemicals were obtained from Merck Chemicals Ltd., Southampton, UK.

2.2. Extraction Method

2.2.1. Soxhlet Extraction

Fatty acids were extracted from ground BSG using a Soxhlet extraction system with a solvent mixture. The extraction lasted for 5 h, with the solvents maintained at their respective boiling points.
Three solvents were used in a 20:50:1 ratio (n-hexane/diethyl ether/formic acid). After extraction, excess solvent was removed using a rotary evaporator at 40 °C overnight [29,30].

2.2.2. Recrystallization Extraction

A modified recrystallization technique was used to extract phenolics and flavonoids [31]. The BSG samples were mixed with ammonium sulfate and monopotassium phosphate (1:2) in distilled water in an Erlenmeyer flask, followed by ultrasonication at 40 °C for 1 h. After extraction, the solution was transferred into ice-cold water to allow precipitation. The resulting crystals were filtered, collected, and freeze-dried for further analysis [32].

2.2.3. Salting-Out Techniques

Protein and lactic acid were separated using a modified salting-out technique [33]. The sample was incubated overnight at room temperature in a 2% (NH4)2SO4 solution [34]. After protein precipitation, the sample was filtered, and the filtrate was mixed with a 2% MgSO4 solution and acetone in a 1:2:1 ratio. The resulting white precipitate was dissolved and stored at 4 °C in a refrigerator for further analysis.
Dietary fiber was extracted using an alkaline pretreatment method [35,36,37]. The BSG sample was treated with a 5% NaOH solution, followed by ultrasonication at 1000 Hz for 1 h. The treated sample was filtered, and the filtrate was mixed with ethanol (1:1 ratio) to precipitate dietary fiber [38,39].

2.3. Measurement and Quantification

2.3.1. High-Performance Liquid Chromatography

HPLC analysis was conducted using a Column Oven CTO-20AC (Shimadzu, Tokyo, Japan), ERC Refracto Max520 Chromatography Software, (Chromeleon 7.2, Revision 1.0, Thermo Scientific, Waltham, MA, USA) and a CBM-20A System Controller (Shimadzu, Tokyo, Japan) [40]. Each extracted sample was dissolved in HPLC-grade methanol (50 µg/mL).
A C18 column (5 µm, 4.6 × 250 mm) was used, with solvent A as methanol and solvent B as 1% acetic acid in water. The gradient program started at 60% solvent A, gradually adjusting over 5 to 20 min to 35%, 10%, and then back to 60% solvent A. The flow rate was set at 1 mL/min, and UV detection was performed at 280 nm and 360 nm.

Determination of Hemicellulose, Lignin, and Cellulose

Cellulose, hemicellulose, and lignin are high-molecular-weight compounds that require hydrolysis or pretreatment before effective HPLC analysis. Each extracted sample was therefore dissolved in HPLC-grade methanol (5 µg/mL).
Before analysis, the sample was adjusted to pH 12 [41,42] using a strong alkaline solution to ensure complete dissolution of cellulose. A C18 column (5 µm, 4.6 × 250 mm) was used, with solvent A as methanol and solvent B as 1% acetic acid in water. The gradient program followed the same settings as the previous HPLC analysis, and UV detection was performed at 280 nm and 360 nm [43].

2.3.2. Gas Chromatography-A Flame Ionization Detector

For fatty acid analysis, each sample was dissolved in acetone (5 µg/mL). The column temperature was initially set to 120 °C, increased at 5–10 °C per minute, reaching 210 °C within 15 min, 250 °C within 12–15 min, and 270 °C within 15–20 min. A ZB-5 column (30 m, 0.25 mm I.D., 0.25 µm film thickness) from Phenomenex, Torrance, CA, USA, was used for analysis [44].

2.3.3. Fourier-Transform Infrared Spectroscopy

FTIR spectroscopy was performed using a Shimadzu FTIR-8400S (Kyoto, Japan) to analyze the surface chemistry and structural features of BSG-derived extracts. Approximately 1 mg of fiber was scanned across a wavelength range of 500–4000 nm.

2.3.4. Fiber, Phenolic, and Antioxidant Quantitative Test

Total dietary fiber was measured using the Total Dietary Fiber Assay Kit (Sigma-Aldrich, St. Louis, MO, USA). The sample was defatted (if the fat content exceeded 10%), dried, and ground to a uniform particle size. Alpha-amylase was added, and the mixture was heated at 95 °C for 15 min. After cooling, the pH was adjusted to 7.5, and protease was added for digestion at 60 °C for 30 min. The sample was further treated with amyl glucosidase at 60 °C for 30 min, then mixed with ethanol (1:1 ratio) to precipitate dietary fiber.
Protein weight (P) was determined using the Kjeldahl method [45], and Ash weight (A) was measured using the crude fiber method [46]. The final dietary fiber content was calculated using the following formulas:
Residue Weight = W2 − W1
Ash Weight = W3 − W1
B = R Blank − P Blank − A Blank
% TDF = [(R Sample − P Sample − A Sample − B)/SW] × 100
Weight Definitions:
W1 = Celatom + Crucible Weight
W2 = Residue + Celatom + Crucible Weight
W3 = Ash + Celatom + Crucible Weight
  • B = Blank Correction
  • R = Residue Weight
  • P = Protein Weight
  • A = Ash weight
  • SW = Sample Weight
For the phenolic compound and antioxidant assays, samples were diluted to fit within the standard curve range. A standard curve was prepared using a 1 mM catechin standard solution, with concentrations ranging from 0 to 10 nmol per well in a 96-well plate. For the reaction, 20 µL of PC Probe was added to each standard and sample well, 20 µL of PC Assay Buffer was added to background wells, and 80 µL of PC Assay Buffer was added to all wells. The plate was gently shaken to ensure even distribution and was incubated at room temperature for 10 min before absorbance was measured at 480 nm. Background absorbance was subtracted, and the standard curve was used to calculate the phenolic compound concentration, expressed as mM catechin equivalents.
For antioxidant quantification, liquid samples were prepared directly, while cell lysates were processed by homogenizing in ice-cold PBS, centrifuged at 14,000 rpm for 10 min, and the clear supernatant was used. A 1 mM Trolox standard solution was prepared, and standard concentrations ranged from 0 to 1000 µM. The reaction mix consisted of 100 µL of Reagent A and 8 µL of Reagent B per well. In a 96-well plate, 20 µL of each standard and sample were added, followed by 100 µL of the reaction mix. The plate was gently mixed, incubated for 10 min, and absorbance was measured at 570 nm. The standard curve was used to determine Total Antioxidant Capacity (TAC), expressed as µM Trolox equivalents.

3. Results and Discussion

3.1. Measuring and Quantifying Fibers

During this investigation, the optimized salting-out fiber extraction [47] method was used. The extracted materials were analyzed, and the total sample weight was 15,000 mg. The results showed an average residue weight of 13,299 mg, an average protein weight of 11,000 mg, an average Ash weight of 1802 mg, and a blank measurement of 258.5 mg.
Table 1 shows that an extraction rate of 93.3% of total dietary fiber (TDF) was achieved. This is a very similar extraction rate compared to that by Wang et al., who reported that the extraction rate of total dietary fiber from kiwi fruit utilizing an alkaline technique was 92.9% [48].
Compared with Wang’s group, the BSG in this study had a more loosely bound fiber structure because it was pretreated during the brewing process, which partially degraded the cellulose and lignin structure, making extraction easier [49].
Furthermore, BSG was particularly rich in water-soluble dietary fiber [50], which increased solubility during alkaline treatment [51], resulting in a better extraction yield. In this study, a modest 5% NaOH concentration successfully eliminated non-fiber components (such as lignin) while also stimulating cellulose disintegration and preserving its structure and function.
Although both studies used alkaline treatment, this research applied ultrasound-assisted treatment, which induced cavitation effects to break cell wall structures and accelerate the release and separation of dietary fibers.
Ultrasound-assisted treatment caused cavitation effects, which broke cell wall structures and accelerated fiber release and separation. Furthermore, using 1:1 ethanol for precipitation effectively isolated high-purity dietary fiber, reduced interference from other components, and resulted in a larger extraction yield.
Furthermore, it was important to analyze what kind of fiber had been extracted. Garside et al. reported that FTIR could be used to analyze the chemical composition of fibers [52], which was similar to Collins et al., who showed that FTIR could measure the variation in the chemical composition of fibers in wheat straw [53].
The obtained FTIR and BSG extract spectra are shown in Table 2 and Figure 2. Table 2 provides the chemical groups in fibers that were examined. Peaks at 1030 cm−1 and 1160 cm−1 represent hemicellulose’s C-O-C stretching vibration and C-O-O stretching vibration [54]. The peak at 1723 cm−1 is attributed to a hemicellulose acetyl or uronic ester group [55]. In plant cell walls, hemicellulose is an amorphous structure that is usually present along with fibers. Xylan, polygalactias glucomannans, poly arabino galactose, glucomannan, and poly-glucomannan are among the common polysaccharides that make up hemicellulose. Hemicellulose is easily impacted by acid or alkali to undergo auto-hydrolysis because of its non-crystal structure and weak bond node connections. The group C-O-C, formed following lipidation or etherification, is the signal produced by the ether bond upon the vibration of glycoside. C-O-C is the glycoside’s primary characteristic peak, and sugar is the main component of the fiber. Etherified hemi fibers are manufactured in the industry to provide biodegradable hydrophobic materials [56]. Etherified hemi fibers in the food industry has enormous potential as environmentally friendly packaging to preserve food shelf life [57,58]. The peak at 1380 cm−1 represents CH3 and CH deformation [59]. It is assumed that the extracted fibers are macromolecular fibers with strong flexibility, generally good elasticity, and easy deformation. The structure is not easily packed well, based on the distinctive detection peaks of CH3 and CH deformation [60]. In food science, previous studies point to macromolecular fiber for its lipid-lowering potential [61].
The N-H bending vibration of amide II and the C=O stretching vibration of amide I, respectively, peaked at 1540 cm−1 and 1657 cm−1. Protein backbone vibrational bands are also provided by amide II, which is primarily driven by in-plane N-H bending. The amide I band, which primarily investigates stretching vibrations of the C=O bonds in the peptide backbone, is the most efficient and often employed band in the research of protein secondary structures [62]. However, the chemicals are speculated to be too strong to disrupt the secondary structure of the protein upon extraction since the C-N stretch bending was not found [63]. This proved that the protein structure was damaged and not fully extracted. Furthermore, any remaining protein had a negative effect on the angle at which the fibers were extracted and interfered with future quantification studies of the fibers. Peak 2700 cm−1 was attributed to bending OH vibrations for tannins [64]. Both tannins and tannic acid are polyphenolic compounds capable of forming extremely complex chemical structures, which made it challenging to interpret the map. However, the stretched area (3000 to 2700 cm−1) of the primary functional groups of tannins, according to prior research, primarily provided information about the spatial arrangement and interactions of hydroxyl substituents, furthering our understanding of critical diagnostic factors for tannins. Peak 3290 cm−1 represents the vibration of the OH group of cellulose [65], while peak 2853 cm−1 represents the asymmetric and symmetric CH2 and CH3 of epoxy resin [66].
According to FTIR peaks (Figure 2), there are numerous compounds of hemicellulose, lignin, and cellulose. The characteristics of these chemical groups, such as hemicellulose biodegradability, macromolecular fiber elasticity, lipid degradation potential, and cellulose’s stable structure, make them suitable for use in sustainable food packaging and functional food development. These chemicals not only extend the shelf life of food but also improve its nutritional content, creating a circular economy by providing innovative solutions that merge food science with environmentally friendly materials.
Therefore, hemicellulose, lignin, and cellulose are the three main types of fibers extracted in this study. Based on these three fibers—hemicellulose, lignin, and cellulose—further quantification was conducted.
Previous studies reported that hemicellulose, lignin, and cellulose were quantified using HPLC [67,68,69]. It was mentioned that the sample weighed 15,000 mg. The qualitative phytochemical profiling of the hemicellulose, lignin, and cellulose present in the BSG extracts, along with their peak area percentage and molecular formula, is provided in Table 3.
The top three significant compounds were hemicellulose (8245.2 mg/L), lignin (10,432.4 mg/L), and cellulose (13,245.4 mg/L). The extraction rates were 54.9%, 69.5%, and 88.3%, respectively.
Table 4 shows that Pal et al. used NH3 in a water-THF solvent to remove lignin from rice straw, achieving a removal rate of 60% [70]. A 65.81% recovery rate was reported for lignin extraction from bamboo using optimized ultrasound-assisted extraction [71]. Compared with this study, which achieved a lignin extraction rate of 69.5%, the results of other studies were significantly lower. The extraction rate of hemicellulose in this study was 54.9%, and the extraction rate for cellulose was 88.3%, compared with a 32.57% hemicellulose removal rate and an 81.2% cellulose removal rate from bagasse using hydrothermal pretreatment [72]. It was clear that this study achieved a higher extraction yield.
The variances could be attributed to multiple factors, such as extraction methods, extraction duration, fiber source, or material variations. However, the results of this study showed that the method applied was simpler and capable of obtaining large amounts of cellulose, making it a suitable reference for factory applications.

3.2. Quantification of Phenolic Compounds and Antioxidants

Numerous scholarly studies in the field of extracted phenolic compounds and antioxidant analysis from agricultural waste have delved into the complex challenges of isolating these compounds while carefully avoiding the unintended introduction of pollutants [73,74].
The total phenolic content was quantified using a Phenolic Compounds Assay Kit, and the results showed 64 mg/L. Antioxidant results showed 24 mg/L using an Antioxidant Assay Kit. The extraction rates were 0.52% and 0.24% for phenolic compounds and antioxidants, respectively.
It is evident that the extraction rates of total phenolic compounds and total antioxidants are relatively low.
The low extraction yields could be attributed to limitations in the recrystallization extraction method [75,76]. Chemicals used in the process might have led to the natural degradation of the target compounds during extraction. Additionally, based on the HPLC chromatogram, the noise levels were relatively low, and fewer unknown peaks appeared compared to the GC-FID results. This indicates that the purity of the extracted compounds in the HPLC analysis is likely higher. The lower noise and fewer unidentified signals in the HPLC chromatogram suggest that the extraction and purification steps might have been more effectively performed. However, some researchers suggest the use of ultrasound-assisted extraction (UAE) [77], which reduces solvent usage, is environmentally friendly, and increases productivity.
Similarly, previous studies often employed the strategy of selecting chemicals for solid extraction according to the particular compound being examined [78,79]. The qualitative phytochemical profiling of the bioactive compounds present in the BSG extracts, including their peak area percentage and molecular formula, is presented in Figure 3. Based on abundance, the top four significant compounds are oleanolic acid (0.243 mg/L), oleic acid (0.057 mg/L), linoleic acid (0.547 mg/L), and arachidic acid (0.1737 mg/L) in Table 5.
The goal was to extract linoleic acid and oleanolic acid from BSG samples through Soxhlet extraction, which aligns with the objectives of analogous studies conducted by Al et al. and Rahim et al. [80,81]. The selection of n-hexane, diethyl ether, and formic acid for extracting linoleic acid and oleanolic acid closely reflects established conventions in the field [82,83]. In line with the varying levels of linoleic acid and oleanolic acid in BSG, as evidenced by numerous prior studies [84], Ruiz-Ruiz et al. extracted oleanolic acid (0.0244 mg/L) by solid–liquid extraction [85]. The extraction results of this study show a significantly higher concentration of oleanolic acid than the value reported by Ruiz-Ruiz et al.
Compared to previous studies, Ruiz-Ruiz et al. reported an oleanolic acid yield of 0.0244 (mg/L) using solid–liquid extraction, which is significantly lower than the yield obtained in this study.
The differences could be due to various factors, including the extraction methods, the duration of extraction of the source of linoleic acid, or variations in the materials used. In line with prior research efforts [29,86], the possible constraints associated with conventionally extracted products are acknowledged.
Soxhlet extraction is highly effective in isolating lipid-based compounds; however, it does not efficiently break down cell wall structures, which can limit the release of bound phenolic acids and antioxidants. Since the extraction process must preserve the integrity of bioactive compounds while enhancing yield, alternative methods should be considered.
On the other hand, the top six key compounds were ascorbic acid (1.5923 mg/L), gallic acid (2.314 mg/L), catechol (2.739 mg/L), ellagic acid (162.88 mg/L), acetylsalicylic acid (0.63 mg/L), and vanillin (590.1688 mg/L). The 45.8% extraction rate of vanillin, as shown in Figure 4 and Table 6, displays a few unknown peaks that will need further investigation.
Vanillin plays an important function in the food sector by increasing the sensory appeal of baked goods, ice cream, and beverages [87]. It is important to point out that customers have recently sought “natural food additives” [88]. Consequently, the successful extraction of vanillin in this study has practical applications.
The chromatographic analysis, consistent with previous studies [89], revealed a range of compounds, including those exhibiting different polarities, aligning with the established knowledge within the field [40].
The qualitative analysis of phytochemicals, as depicted in Table 6, aligns with previous research by Wang [90] as well as Sun et al. [91]. These results emphasize the existence of important bioactive compounds within BSG extracts. The detection of vanillin and ellagic acid as the primary compounds aligns with the findings of other researchers in this field [92]. The selection of ethanol and methanol as solvents for extracting vanillin and ellagic acid reflects established conventions in the field [93,94].
Regarding the fluctuations in the levels of vanillin and ellagic acid within BSG, as reported in several preceding investigations, Lopes et al. extracted vanillin 109.2 (mg/L) by solvent extraction [95], while Bonifacio-Lopes et al. extracted vanillin 27.80 ± 0.49 (mg/L) by ohmic extracts [96].
The results of our study demonstrate a considerably higher concentration of vanillin compared to the other two studies. Specifically, our extraction yielded a concentration more than 5 times higher than the value reported by Lopes et al. and over 20 times higher than the value from Bonifacio-Lopes et al. These variations could be attributed to differences in the extraction methods, the source of the vanillin, or variations in the experimental conditions between the studies.
However, it is regrettable that within the existing body of research, there is a notable lack of studies that have identified ellagic acid as a primary target compound in the context of BSG. It is important to note that BSG is primarily used as animal feed, compost, or for other agricultural purposes, and not typically as a source of ellagic acid extraction [97].
In accordance with the discoveries made by earlier investigators [98,99], our study recognizes the potential limitations linked to traditionally extracted products. Therefore, the aims of this study were to investigate alternative extraction methods in upcoming experiments.
This study also aimed to explore more efficient alternative extraction techniques to enhance yield and product quality. Additionally, beyond improving extraction methods, industrial scalability is also a crucial consideration, particularly in overcoming challenges related to cost and environmental impact.
Scaling up the process presents challenges, such as increased solvent usage, leading to higher costs and environmental risks. Solvent recovery systems can help mitigate these issues to some extent. Soxhlet extraction proved to be inefficient, so countercurrent extraction was adopted to improve efficiency. Although these methods may increase costs, semi-continuous or automated systems can enhance overall process efficiency.

4. Conclusions and Future Work

This study successfully demonstrated the potential of various extraction methods, including Soxhlet extraction, recrystallization, salting-out, and alkaline pretreatment, for recovering valuable bioactive compounds from BSG. The results confirmed that BSG is a rich source of dietary fibers, phenolic acids, and antioxidants, with fiber extraction achieving a high yield.
By converting BSG into high-value compounds, this research contributed to sustainable waste management and resource conservation. However, challenges remained due to the complex structural matrix of BSG, necessitating advanced pretreatment methods. A mild alkaline pretreatment (5% NaOH) and ultrasound-assisted extraction improved fiber release and separation, while ethanol precipitation enhanced purity. Although phenolic acids and antioxidants were successfully extracted, their yields remained suboptimal, highlighting the need for further optimization [99,100].
This study emphasized the importance of scaling up extraction methods, as factors such as efficiency, purity, and compound stability must be improved for commercial viability. The valorization of BSG aligns with circular economy principles, reducing environmental pollution and supporting sustainability initiatives. Future research should explore alternative extraction techniques, such as enzymatic and supercritical CO2 extraction, to enhance efficiency while minimizing environmental impact.
Additionally, preserving the bioactivity of extracted compounds and assessing their applications in food, cosmetics, and pharmaceuticals remain key areas for further investigation.
This study directly supports SDG 12 (Responsible Consumption and Production) and SDG 2 (Zero Hunger) by repurposing BSG into valuable nutritional components, promoting food security [101]. It also aligns with SDG 13 (Climate Action) [102] by reducing waste and carbon emissions. Future research should extend these findings to other bioactive-rich food waste streams, such as fruit peels and coffee grounds, further advancing sustainability and circular economy practices.
The findings of this study can be extended to other bioactive-rich food waste streams, such as fruit peels, coffee grounds, and soybean residue, to further enhance resource utilization and sustainability. To achieve this, future research should assess the applicability of these extraction methods to various food waste sources by evaluating their bioactive compound profiles and determining the most suitable extraction strategies.

Author Contributions

Conceptualization, T.M.; Writing—original draft, H.-Y.I.C.; Writing—review & editing, H.O. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Chattaraj, S.; Mitra, D.; Ganguly, A.; Thatoi, H.; Mohapatra, P.K.D. A critical review on the biotechnological potential of Brewers’ waste: Challenges and future alternatives. Curr. Res. Microb. Sci. 2024, 6, 100228. [Google Scholar] [CrossRef] [PubMed]
  2. Arellano, L.I.T. Travail de Fin d’études: Exploring the Supply Chain for Brewery’s By-Product Recycling: A Study on a Potential Alternative for a Brewery’s By-Product Valorization. 2023. Available online: https://matheo.uliege.be/handle/2268.2/17802 (accessed on 6 January 2025).
  3. Karlović, A.; Jurić, A.; Ćorić, N.; Habschied, K.; Krstanović, V.; Mastanjević, K. By-products in the malting and brewing industries—Re-usage possibilities. Fermentation 2020, 6, 82. [Google Scholar] [CrossRef]
  4. Zeko-Pivač, A.; Tišma, M.; Žnidaršič-Plazl, P.; Kulisic, B.; Sakellaris, G.; Hao, J.; Planinić, M. The potential of brewer’s spent grain in the circular bioeconomy: State of the art and future perspectives. Front. Bioeng. Biotechnol. 2022, 10, 870744. [Google Scholar] [CrossRef] [PubMed]
  5. Lemaire, A. Circular Economy: Best Practices and Future Perspectives for the Beer Brewing Industry; Louvain School of Management, Université Catholique de Louvain: Ottignies-Louvain-la-Neuve, Belgium, 2020; p. 24674. Available online: https://dial.uclouvain.be/downloader/downloader.php?pid=thesis%3A24674&datastream=PDF_01 (accessed on 29 November 2024).
  6. Lynch, K.M.; Steffen, E.J.; Arendt, E.K. Brewers’ spent grain: A review with an emphasis on food and health. J. Inst. Brew. 2016, 122, 553–568. [Google Scholar] [CrossRef]
  7. Connolly, A. Generation and Characterisation of Novel Health Enhancing Ingredients from Brewers’ Spent Grain (BSG). Ph.D. Thesis, University of Limerick, Limerick, Ireland, 2013. [Google Scholar]
  8. Olagunju, A.I.; Omoba, O.S. High fibres functional products. In Functional Cereals and Cereal Foods: Properties, Functionality and Applications; Springer: Berlin/Heidelberg, Germany, 2022; pp. 379–400. [Google Scholar]
  9. Radoš, K.; Čukelj Mustač, N.; Varga, K.; Drakula, S.; Voučko, B.; Ćurić, D.; Novotni, D. Development of high-fibre and low-FODMAP crackers. Foods 2022, 11, 2577. [Google Scholar] [CrossRef]
  10. Naibaho, J.; Korzeniowska, M.; Wojdyło, A.; Ayunda, H.M.; Foste, M.; Yang, B. Techno-functional properties of protein from protease-treated brewers’ spent grain (BSG) and investigation of antioxidant activity of extracted proteins and BSG residues. J. Cereal Sci. 2022, 107, 103524. [Google Scholar] [CrossRef]
  11. McCarthy, A.L.; O’Callaghan, Y.C.; Piggott, C.O.; FitzGerald, R.J.; O’Brien, N.M. Brewers’ spent grain; bioactivity of phenolic component, its role in animal nutrition and potential for incorporation in functional foods: A review. Proc. Nutr. Soc. 2013, 72, 117–125. [Google Scholar] [CrossRef]
  12. Choudhary, P.; Devi, T.B.; Tushir, S.; Kasana, R.C.; Popatrao, D.S.; K, N. Mango seed kernel: A bountiful source of nutritional and bioactive compounds. Food Bioprocess Technol. 2023, 16, 289–312. [Google Scholar] [CrossRef]
  13. Das, G.; Nath, R.; Das Talukdar, A.; Ağagündüz, D.; Yilmaz, B.; Capasso, R.; Shin, H.-S.; Patra, J.K. Major bioactive compounds from java plum seeds: An investigation of its extraction procedures and clinical effects. Plants 2023, 12, 1214. [Google Scholar] [CrossRef]
  14. Kovácik, A.; Kopecná, M.; Hrdinová, I.; Opálka, L.; Bettex, M.B.; Vávrová, K. Time-Dependent Differences in the Effects of Oleic Acid and Oleyl Alcohol on the Human Skin Barrier. Mol. Pharm. 2023, 20, 6237–6245. [Google Scholar] [CrossRef]
  15. Rudrapal, M.; Khairnar, S.J.; Khan, J.; Dukhyil, A.B.; Ansari, M.A.; Alomary, M.N.; Alshabrmi, F.M.; Palai, S.; Deb, P.K.; Devi, R. Dietary polyphenols and their role in oxidative stress-induced human diseases: Insights into protective effects, antioxidant potentials and mechanism (s) of action. Front. Pharmacol. 2022, 13, 806470. [Google Scholar] [CrossRef]
  16. He, X.; Wan, F.; Su, W.; Xie, W. Research progress on skin aging and active ingredients. Molecules 2023, 28, 5556. [Google Scholar] [CrossRef]
  17. Sun, J. The Effect Of Ellagic Acid On Anti-Aging. MedScien 2024, 1, 1–7. [Google Scholar] [CrossRef]
  18. Mucha, P.; Skoczyńska, A.; Małecka, M.; Hikisz, P.; Budzisz, E. Overview of the antioxidant and anti-inflammatory activities of selected plant compounds and their metal ions complexes. Molecules 2021, 26, 4886. [Google Scholar] [CrossRef]
  19. Barcelos, M.C.; Ramos, C.L.; Kuddus, M.; Rodriguez-Couto, S.; Srivastava, N.; Ramteke, P.W.; Mishra, P.K.; Molina, G. Enzymatic potential for the valorization of agro-industrial by-products. Biotechnol. Lett. 2020, 42, 1799–1827. [Google Scholar] [CrossRef]
  20. Zheng, Q.; Zhou, T.; Wang, Y.; Cao, X.; Wu, S.; Zhao, M.; Wang, H.; Xu, M.; Zheng, B.; Zheng, J. Pretreatment of wheat straw leads to structural changes and improved enzymatic hydrolysis. Sci. Rep. 2018, 8, 1321. [Google Scholar] [CrossRef]
  21. Merali, Z.; Collins, S.R.; Elliston, A.; Wilson, D.R.; Käsper, A.; Waldron, K.W. Characterization of cell wall components of wheat bran following hydrothermal pretreatment and fractionation. Biotechnol. Biofuels 2015, 8, 23. [Google Scholar] [CrossRef]
  22. Kristensen, J.B.; Thygesen, L.G.; Felby, C.; Jørgensen, H.; Elder, T. Cell-wall structural changes in wheat straw pretreated for bioethanol production. Biotechnol. Biofuels 2008, 1, 5. [Google Scholar] [CrossRef]
  23. Chen, X.; Guo, Y.; Song, T.; Dou, Y.; Zhang, J.; Zhang, X.; Dou, H. Investigation on the stability of low-density lipoproteins modified by phospholipase A2 using asymmetrical flow field-flow fractionation. J. Food Meas. Charact. 2021, 15, 3350–3356. [Google Scholar] [CrossRef]
  24. Fărcaș, A.C.; Socaci, S.A.; Nemeș, S.A.; Pop, O.L.; Coldea, T.E.; Fogarasi, M.; Biriș-Dorhoi, E.S. An update regarding the bioactive compound of cereal by-products: Health benefits and potential applications. Nutrients 2022, 14, 3470. [Google Scholar] [CrossRef]
  25. Sharifi-Rad, M.; Anil Kumar, N.V.; Zucca, P.; Varoni, E.M.; Dini, L.; Panzarini, E.; Rajkovic, J.; Tsouh Fokou, P.V.; Azzini, E.; Peluso, I. Lifestyle, oxidative stress, and antioxidants: Back and forth in the pathophysiology of chronic diseases. Front. Physiol. 2020, 11, 694. [Google Scholar] [CrossRef]
  26. Birsan, R. Enrichment of Brewer’s Spent Grain Polyphenols and Assessment of Their Role in Inhibition of Cholinesterases, Amylase and Glucosidase. Ph.D. Thesis, University of East Anglia, Norwich, UK, 2022. [Google Scholar]
  27. Klepacka, J.; Fornal, Ł. Ferulic acid and its position among the phenolic compounds of wheat. Crit. Rev. Food Sci. Nutr. 2006, 46, 639–647. [Google Scholar] [CrossRef]
  28. Marchiosi, R.; dos Santos, W.D.; Constantin, R.P.; de Lima, R.B.; Soares, A.R.; Finger-Teixeira, A.; Mota, T.R.; de Oliveira, D.M.; Foletto-Felipe, M.d.P.; Abrahão, J. Biosynthesis and metabolic actions of simple phenolic acids in plants. Phytochem. Rev. 2020, 19, 865–906. [Google Scholar] [CrossRef]
  29. Daud, N.M.; Putra, N.R.; Jamaludin, R.; Norodin, N.S.M.; Sarkawi, N.S.; Hamzah, M.H.S.; Nasir, H.M.; Zaidel, D.N.A.; Yunus, M.A.C.; Salleh, L.M. Valorisation of plant seed as natural bioactive compounds by various extraction methods: A review. Trends Food Sci. Technol. 2022, 119, 201–214. [Google Scholar] [CrossRef]
  30. Agapay, R.C.; Ju, Y.H.; Tran-Nguyen, P.L.; Ismadji, S.; Angkawijaya, A.E.; Go, A.W. Process evaluation of solvent-free lipase-catalyzed esterification schemes in the synthesis of structured triglycerides from oleic and palmitic acids. Asia-Pac. J. Chem. Eng. 2021, 16, e2606. [Google Scholar] [CrossRef]
  31. Liu, J.; Wang, F.F.; Jiang, Z.M.; Liu, E.H. Identification of antidiabetic components in Uncariae Rammulus Cum Uncis based on phytochemical isolation and spectrum–effect relationship analysis. Phytochem. Anal. 2022, 33, 659–669. [Google Scholar] [CrossRef]
  32. Chen, P.-C.; Dlamini, B.S.; Chen, C.-R.; Kuo, Y.-H.; Shih, W.-L.; Lin, Y.-S.; Lee, C.-H.; Chang, C.-I. Structure related α-glucosidase inhibitory activity and molecular docking analyses of phenolic compounds from Paeonia suffruticosa. Med. Chem. Res. 2022, 31, 293–306. [Google Scholar] [CrossRef]
  33. Burgess, R.R. Protein precipitation techniques. Methods Enzymol. 2009, 463, 331–342. [Google Scholar] [CrossRef]
  34. Duong-Ly, K.C.; Gabelli, S.B. Salting out of proteins using ammonium sulfate precipitation. In Methods in Enzymology; Elsevier: Amsterdam, The Netherlands, 2014; Volume 541, pp. 85–94. [Google Scholar]
  35. de Oliveira, D.N.; Claro, P.I.; de Freitas, R.R.; Martins, M.A.; Souza, T.M.; Silva, B.M.; Mendes, L.M.; Bufalino, L. Enhancement of the Amazonian açaí waste fibers through variations of alkali pretreatment parameters. Chem. Biodivers. 2019, 16, e1900275. [Google Scholar] [CrossRef]
  36. Zhao, S.; Baik, O.-D.; Choi, Y.J.; Kim, S.-M. Pretreatments for the efficient extraction of bioactive compounds from plant-based biomaterials. Crit. Rev. Food Sci. Nutr. 2014, 54, 1283–1297. [Google Scholar] [CrossRef]
  37. Kumar, P.; Barrett, D.M.; Delwiche, M.J.; Stroeve, P. Methods for pretreatment of lignocellulosic biomass for efficient hydrolysis and biofuel production. Ind. Eng. Chem. Res. 2009, 48, 3713–3729. [Google Scholar] [CrossRef]
  38. Akyüz, A.; Tekin, İ.; Aksoy, Z.; Ersus, S. Plant Protein Resources, Novel Extraction and Precipitation Methods: A Review. J. Food Process Eng. 2024, 47, e14758. [Google Scholar] [CrossRef]
  39. Xie, S.; Li, Z.; Zhang, W. Techno-Economic Analysis of Upgrading Corn Stover-Based Acetone, n-Butanol, and Ethanol to Higher Ketones and Alcohols: Fuels or Fine Chemicals? ACS Sustain. Chem. Eng. 2023, 11, 3474–3485. [Google Scholar] [CrossRef]
  40. Mradu, G.; Saumyakanti, S.; Sohini, M.; Arup, M. HPLC profiles of standard phenolic compounds present in medicinal plants. Int. J. Pharmacogn. Phytochem. Res. 2012, 4, 162–167. [Google Scholar]
  41. Dubuis, A.; Le Masle, A.; Chahen, L.; Destandau, E.; Charon, N. Centrifugal partition chromatography as a fractionation tool for the analysis of lignocellulosic biomass products by liquid chromatography coupled to mass spectrometry. J. Chromatogr. A 2019, 1597, 159–166. [Google Scholar] [CrossRef]
  42. Reza, M.T.; Rottler, E.; Herklotz, L.; Wirth, B. Hydrothermal carbonization (HTC) of wheat straw: Influence of feedwater pH prepared by acetic acid and potassium hydroxide. Bioresour. Technol. 2015, 182, 336–344. [Google Scholar] [CrossRef]
  43. Reymond, C.; Dubuis, A.; Le Masle, A.; Colas, C.; Chahen, L.; Destandau, E.; Charon, N. Characterization of liquid–liquid extraction fractions from lignocellulosic biomass by high performance liquid chromatography hyphenated to tandem high-resolution mass spectrometry. J. Chromatogr. A 2020, 1610, 460569. [Google Scholar] [CrossRef]
  44. Zhang, H.; Wang, Z.; Liu, O. Development and validation of a GC–FID method for quantitative analysis of oleic acid and related fatty acids. J. Pharm. Anal. 2015, 5, 223–230. [Google Scholar] [CrossRef]
  45. McCleary, B.V.; McLoughlin, C. Determination of Insoluble, Soluble, and Total Dietary Fiber in Foods Using a Rapid Integrated Procedure of Enzymatic-Gravimetric-Liquid Chromatography: First Action 2022.01. J. AOAC Int. 2023, 106, 127–145. [Google Scholar] [CrossRef]
  46. Bird, D.; Ho, S. Nutritive values of whole-animal diets for captive birds of prey. J. Raptor Res. 2024, 10, 2. [Google Scholar]
  47. Myrvold, B.O. Salting-out and salting-in experiments with lignosulfonates (LSs). Holzforschung 2013, 67, 549–557. [Google Scholar] [CrossRef]
  48. Wang, K.; Li, M.; Wang, Y.; Liu, Z.; Ni, Y. Effects of extraction methods on the structural characteristics and functional properties of dietary fiber extracted from kiwifruit (Actinidia deliciosa). Food Hydrocoll. 2021, 110, 106162. [Google Scholar] [CrossRef]
  49. Gupta, M.; Abu-Ghannam, N.; Gallaghar, E. Barley for Brewing: Characteristic Changes during Malting, Brewing and Applications of Its By-Products. Compr. Rev. Food Sci. Food Saf. 2010, 9, 318–328. [Google Scholar] [CrossRef] [PubMed]
  50. Ikram, S.; Huang, L.; Zhang, H.; Wang, J.; Yin, M. Composition and nutrient value proposition of brewers spent grain. J. Food Sci. 2017, 82, 2232–2242. [Google Scholar] [CrossRef]
  51. Naibaho, J.; Korzeniowska, M. Brewers’ spent grain in food systems: Processing and final products quality as a function of fiber modification treatment. J. Food Sci. 2021, 86, 1532–1551. [Google Scholar] [CrossRef]
  52. Garside, P.; Wyeth, P. Identification of cellulosic fibres by FTIR spectroscopy-thread and single fibre analysis by attenuated total reflectance. Stud. Conserv. 2003, 48, 269–275. [Google Scholar] [CrossRef]
  53. Collins, S.R.; Wellner, N.; Martinez Bordonado, I.; Harper, A.L.; Miller, C.N.; Bancroft, I.; Waldron, K.W. Variation in the chemical composition of wheat straw: The role of tissue ratio and composition. Biotechnol. Biofuels 2014, 7, 121. [Google Scholar] [CrossRef]
  54. Peng, W.; Wang, L.; Ohkoshi, M.; Zhang, M. Separation of hemicelluloses from Eucalyptus species: Investigating the residue after alkaline treatment. Cellul. Chem. Technol. 2015, 49, 756–764. [Google Scholar]
  55. Agwuncha, S.C.; Owonubi, S.; Fapojuwo, D.P.; Abdulkarim, A.; Okonkwo, T.P.; Makhatha, E.M. Evaluation of mercerization treatment conditions on extracted cellulose from shea nut shell using FTIR and thermogravimetric analysis. Mater. Today Proc. 2021, 38, 958–963. [Google Scholar] [CrossRef]
  56. Martins, J.R.; Abe, M.M.; Brienzo, M. Chemical Modification Strategies for Developing Functionalized Hemicellulose: Advanced Applications of Modified Hemicellulose. In Hemicellulose Biorefinery: A Sustainable Solution for Value Addition to Bio-Based Products and Bioenergy; Springer: Berlin/Heidelberg, Germany, 2022; pp. 171–205. [Google Scholar] [CrossRef]
  57. Zhao, Y.; Sun, H.; Yang, B.; Weng, Y. Hemicellulose-based film: Potential green films for food packaging. Polymers 2020, 12, 1775. [Google Scholar] [CrossRef]
  58. Hu, L.; Fang, X.; Du, M.; Luo, F.; Guo, S. Hemicellulose-based polymers processing and application. Am. J. Plant Sci. 2020, 11, 2066–2079. [Google Scholar] [CrossRef]
  59. Kavkler, K.; Šmit, Ž.; Jezeršek, D.; Eichert, D.; Demšar, A. Investigation of biodeteriorated historical textiles by conventional and synchrotron radiation FTIR spectroscopy. Polym. Degrad. Stab. 2011, 96, 1081–1086. [Google Scholar] [CrossRef]
  60. Badii, K.; Church, J.S.; Golkarnarenji, G.; Naebe, M.; Khayyam, H. Chemical structure based prediction of PAN and oxidized PAN fiber density through a non-linear mathematical model. Polym. Degrad. Stab. 2016, 131, 53–61. [Google Scholar] [CrossRef]
  61. Galanakis, C.M. Separation of functional macromolecules and micromolecules: From ultrafiltration to the border of nanofiltration. Trends Food Sci. Technol. 2015, 42, 44–63. [Google Scholar] [CrossRef]
  62. Gallagher, W. FTIR analysis of protein structure. Course Man. Chem 2009, 455, 1–8. [Google Scholar]
  63. Sadat, A.; Joye, I.J. Peak fitting applied to fourier transform infrared and raman spectroscopic analysis of proteins. Appl. Sci. 2020, 10, 5918. [Google Scholar] [CrossRef]
  64. Ricci, A.; Olejar, K.J.; Parpinello, G.P.; Kilmartin, P.A.; Versari, A. Application of Fourier transform infrared (FTIR) spectroscopy in the characterization of tannins. Appl. Spectrosc. Rev. 2015, 50, 407–442. [Google Scholar] [CrossRef]
  65. Asriza, R.; Humaira, D.; Ryaldi, G. Characterization of cellulose acetate functional groups synthesized from corn husk (Zea mays). Proc. IOP Conf. Ser. Earth Environ. Sci. 2021, 926, 012060. [Google Scholar] [CrossRef]
  66. Alamri, H.; Low, I.M. Mechanical properties and water absorption behaviour of recycled cellulose fibre reinforced epoxy composites. Polym. Test. 2012, 31, 620–628. [Google Scholar] [CrossRef]
  67. Barbosa, B.M.; Vaz, S., Jr.; Colodette, J.L.; De Aguiar, A.R.; Cabral, C.P.T.; de Freitas Homem de Faria, B. Structural and chemical characterization of lignin and hemicellulose isolated from corn fibers toward agroindustrial residue valorization. Cellulose 2022, 29, 8117–8132. [Google Scholar] [CrossRef]
  68. Reyes-Rivera, J.; Terrazas, T. Lignin Analysis by HPLC and FTIR: Spectra Deconvolution and S/G Ratio Determination. In Xylem: Methods and Protocols; Springer: Berlin/Heidelberg, Germany, 2023; pp. 149–169. [Google Scholar] [CrossRef]
  69. Ottah, V.E.; Ezugwu, A.L.; Ezike, T.C.; Chilaka, F.C. Comparative analysis of alkaline-extracted hemicelluloses from Beech, African rose and Agba woods using FTIR and HPLC. Heliyon 2022, 8, e09714. [Google Scholar] [CrossRef] [PubMed]
  70. Pal, P.; Li, H.; Saravanamurugan, S. Removal of lignin and silica from rice straw for enhanced accessibility of holocellulose for the production of high-value chemicals. Bioresour. Technol. 2022, 361, 127661. [Google Scholar] [CrossRef] [PubMed]
  71. Das, A.; Mohanty, K. Optimization of lignin extraction from bamboo by ultrasound-assisted organosolv pretreatment. Bioresour. Technol. 2023, 376, 128884. [Google Scholar] [CrossRef] [PubMed]
  72. Wang, N.; Xu, B.; Wang, X.; Lang, J.; Zhang, H. Chemical and structural elucidation of lignin and cellulose isolated using DES from bagasse based on alkaline and hydrothermal pretreatment. Polymers 2022, 14, 2756. [Google Scholar] [CrossRef]
  73. Cho, E.J.; Trinh, L.T.P.; Song, Y.; Lee, Y.G.; Bae, H.-J. Bioconversion of biomass waste into high value chemicals. Bioresour. Technol. 2020, 298, 122386. [Google Scholar] [CrossRef]
  74. Ali, A.; Riaz, S.; Sameen, A.; Naumovski, N.; Iqbal, M.W.; Rehman, A.; Mehany, T.; Zeng, X.-A.; Manzoor, M.F. The disposition of bioactive compounds from fruit waste, their extraction, and analysis using novel technologies: A review. Processes 2022, 10, 2014. [Google Scholar] [CrossRef]
  75. Liu, Y.; Sui, X.; Zhao, X.; Wang, S.; Yang, Q. Antioxidative Activity Evaluation of High Purity and Micronized Tartary Buckwheat Flavonoids Prepared by Antisolvent Recrystallization. Foods 2022, 11, 1346. [Google Scholar] [CrossRef]
  76. Chezanoglou, E.; Goula, A.M. Properties and Stability of Encapsulated Pomegranate Peel Extract Prepared by Co-Crystallization. Appl. Sci. 2023, 13, 8680. [Google Scholar] [CrossRef]
  77. Iadecola, R.; Ciccoritti, R.; Ceccantoni, B.; Bellincontro, A.; Amoriello, T. Optimization of phenolic compound extraction from brewers’ spent grain using ultrasound technologies coupled with response surface methodology. Sustainability 2022, 14, 3309. [Google Scholar] [CrossRef]
  78. Zhang, Y.; Zhao, Z.; Li, W.; Tang, Y.; Meng, H.; Wang, S. Separation and Purification of Taxanes from Crude Taxus cuspidata Extract by Antisolvent Recrystallization Method. Separations 2022, 9, 304. [Google Scholar] [CrossRef]
  79. Salleh, W.M.N.H.W.; Shakri, N.M.; Jauri, M.H.; Nafiah, M.A. Alkaloids and Flavonoids from Polyalthia cauliflora. Chem. Nat. Compd. 2022, 58, 986–988. [Google Scholar] [CrossRef]
  80. Al Juhaimi, F.; Özcan, M.M.; Ghafoor, K.; Babiker, E.E.; Hussain, S. Comparison of cold-pressing and soxhlet extraction systems for bioactive compounds, antioxidant properties, polyphenols, fatty acids and tocopherols in eight nut oils. J. Food Sci. Technol. 2018, 55, 3163–3173. [Google Scholar] [CrossRef] [PubMed]
  81. Rahim, M.A.; Shoukat, A.; Khalid, W.; Ejaz, A.; Itrat, N.; Majeed, I.; Koraqi, H.; Imran, M.; Nisa, M.U.; Nazir, A. A narrative review on various oil extraction methods, encapsulation processes, fatty acid profiles, oxidative stability, and medicinal properties of black seed (Nigella sativa). Foods 2022, 11, 2826. [Google Scholar] [CrossRef] [PubMed]
  82. Shunmugiah Veluchamy, R.; Mary, R.; Beegum Puthiya P, S.; Pandiselvam, R.; Padmanabhan, S.; Sathyan, N.; Shil, S.; Niral, V.; Musuvadi Ramarathinam, M.; Lokesha, A.N. Physicochemical characterization and fatty acid profiles of testa oils from various coconut (Cocos nucifera L.) genotypes. J. Sci. Food Agric. 2023, 103, 370–379. [Google Scholar] [CrossRef]
  83. Boyadzhieva, S.; Coelho, J.A.; Errico, M.; Reynel-Avilla, H.E.; Yankov, D.S.; Bonilla-Petriciolet, A.; Stateva, R.P. Assessment of Gnaphalium viscosum (Kunth) valorization prospects: Sustainable recovery of antioxidants by different techniques. Antioxidants 2022, 11, 2495. [Google Scholar] [CrossRef]
  84. Chetrariu, A.; Ursachi, V.F.; Dabija, A. Evaluation of the fatty acids and amino acids profiles in spent grain from brewing and malt whisky. Sci. Study Res. Chem. Chem. Eng. Biotechnol. Food Ind. 2022, 23, 167–177. [Google Scholar]
  85. Ruiz-Ruiz, J.C.; Aldana, G.d.C.E.; Cruz, A.I.C.; Segura-Campos, M.R. Antioxidant activity of polyphenols extracted from hop used in craft beer. In Biotechnological Progress and Beverage Consumption; Elsevier: Amsterdam, The Netherlands, 2020; pp. 283–310. [Google Scholar] [CrossRef]
  86. Nuchdang, S.; Phruetthinan, N.; Paleeleam, P.; Domrongpokkaphan, V.; Chuetor, S.; Chirathivat, P.; Phalakornkule, C. Soxhlet, microwave-assisted, and room temperature liquid extraction of oil and bioactive compounds from palm kernel cake using isopropanol as solvent. Ind. Crops Prod. 2022, 176, 114379. [Google Scholar] [CrossRef]
  87. Singh, N.; Sudha, M. Natural food flavours: A healthier alternative for bakery industry—A review. J. Food Sci. Technol. 2024, 61, 642–650. [Google Scholar] [CrossRef]
  88. Shemet, V.; Hulai, O. Food additives of natural origin: Short review. Commod. Bull. 2023, 1, 6–18. [Google Scholar] [CrossRef]
  89. Belwal, T.; Cravotto, C.; Ramola, S.; Thakur, M.; Chemat, F.; Cravotto, G. Bioactive compounds from cocoa husk: Extraction, analysis and applications in food production chain. Foods 2022, 11, 798. [Google Scholar] [CrossRef]
  90. Wang, M.; Lu, Y.; Yang, Y.; Yu, J.; Chen, Y.; Tu, F.; Hou, J.; Yang, Z.; Jiang, X. Source identification of vanillin in sesame oil by HPLC-MS/MS. Food Control 2023, 143, 109283. [Google Scholar] [CrossRef]
  91. Sun, Y.; Liu, J.; Bayertai; Tang, S.; Zhou, X. Analysis of gallic acid and ellagic acid in leaves of Elaeagnus angustifolia L. from different habitats and times in Xinjiang by HPLC with cluster analysis. Acta Chromatogr. 2021, 33, 195–201. [Google Scholar] [CrossRef]
  92. Vilas-Franquesa, A.; Casertano, M.; Tresserra-Rimbau, A.; Vallverdú-Queralt, A.; Torres-León, C. Recent advances in bio-based extraction processes for the recovery of bound phenolics from agro-industrial by-products and their biological activity. Crit. Rev. Food Sci. Nutr. 2023, 64, 10643–10667. [Google Scholar] [CrossRef] [PubMed]
  93. Vasquez-Rojas, W.V.; Hernández, D.M.; Cano, M.P.; Reali, T.F. Extraction and Analytical Characterization of Phenolic Compounds from Brazil Nut (Bertholletia excelsa) Skin Industrial by-Product. Trends Sci. 2023, 20, 5457. [Google Scholar] [CrossRef]
  94. El-Shahir, A.A.; El-Wakil, D.A.; Abdel Latef, A.A.H.; Youssef, N.H. Bioactive Compounds and Antifungal Activity of Leaves and Fruits Methanolic Extracts of Ziziphus spina-christi L. Plants 2022, 11, 746. [Google Scholar] [CrossRef]
  95. Lopes, M.T.B.V. Development and Characterization of Functional Ingredients Through Valorization from Brewer’s Spent Grain. P.D. Thesis, University of Minho, Braga, Portugal, University of Aveiro, Aveiro, Portugal, 2022. [Google Scholar]
  96. Bonifacio-Lopes, T.; Vilas-Boas, A.; Machado, M.; Costa, E.M.; Silva, S.; Pereira, R.N.; Campos, D.; Teixeira, J.A.; Pintado, M. Exploring the bioactive potential of brewers spent grain ohmic extracts. Innov. Food Sci. Emerg. Technol. 2022, 76, 102943. [Google Scholar] [CrossRef]
  97. Minervini, F.; Comitini, F.; De Boni, A.; Fiorino, G.M.; Rodrigues, F.; Tlais, A.Z.A.; Carafa, I.; De Angelis, M. Sustainable and Health-Protecting Food Ingredients from Bioprocessed Food by-Products and Wastes. Sustainability 2022, 14, 15283. [Google Scholar] [CrossRef]
  98. Azmir, J.; Zaidul, I.S.M.; Rahman, M.M.; Sharif, K.; Mohamed, A.; Sahena, F.; Jahurul, M.; Ghafoor, K.; Norulaini, N.; Omar, A. Techniques for extraction of bioactive compounds from plant materials: A review. J. Food Eng. 2013, 117, 426–436. [Google Scholar] [CrossRef]
  99. Jha, A.K.; Sit, N. Extraction of bioactive compounds from plant materials using combination of various novel methods: A review. Trends Food Sci. Technol. 2022, 119, 579–591. [Google Scholar] [CrossRef]
  100. Sasidharan, S.; Chen, Y.; Saravanan, D.; Sundram, K.; Latha, L.Y. Extraction, isolation and characterization of bioactive compounds from plants’ extracts. Afr. J. Tradit. Complement. Altern. Med. 2011, 8, 1–10. [Google Scholar] [CrossRef]
  101. Arora, N.K.; Mishra, I. Responsible consumption and production: A roadmap to sustainable development. Environ. Sustain. 2023, 6, 1–6. [Google Scholar] [CrossRef]
  102. Purnell, P.J. A comparison of different methods of identifying publications related to the United Nations Sustainable Development Goals: Case study of SDG 13—Climate Action. Quant. Sci. Stud. 2022, 3, 976–1002. [Google Scholar] [CrossRef]
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Figure 1. Graphical abstract of the experiments for this study.
Figure 1. Graphical abstract of the experiments for this study.
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Figure 2. FTIR result on fiber extracted from BSG. Wavenumber and assignment are shown in Table 1.
Figure 2. FTIR result on fiber extracted from BSG. Wavenumber and assignment are shown in Table 1.
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Figure 3. GC-FID analysis ingredient peak for extracts from BSG waste by conventional solvent extraction. Details of extraction concentration are shown in Table 5.
Figure 3. GC-FID analysis ingredient peak for extracts from BSG waste by conventional solvent extraction. Details of extraction concentration are shown in Table 5.
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Figure 4. The peak determined via HPLC for extracts from BSG by conventional extraction.
Figure 4. The peak determined via HPLC for extracts from BSG by conventional extraction.
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Table 1. Comparison of dietary fiber extraction methods and key enhancements.
Table 1. Comparison of dietary fiber extraction methods and key enhancements.
StudyExtraction MethodTotal Dietary Fiber (TDF) Extraction RateStructural DifferencesKey EnhancementsPrecipitation MethodRef.
This Study (BSG)Salting-out + Ultrasound-assisted alkaline treatment93.3%BSG fiber structure was more loosely bound due to brewing pretreatment, which partially degraded cellulose and ligninUltrasound-assisted treatment induced cavitation effects, breaking cell walls and accelerating fiber release1:1 ethanol precipitation to isolate high-purity dietary fiber
Wang et al. (Kiwi Fruit)Alkaline treatment92.9%Kiwi fruit fiber structure remained more intact as no prior processing was involvedNo ultrasound treatment was appliedNot specified[48]
Table 2. Wavenumber and assignment needed for FTIR analysis of fibers extracted from BSG.
Table 2. Wavenumber and assignment needed for FTIR analysis of fibers extracted from BSG.
Wavenumber (cm−1)Assignment
1030C-O stretching vibration of hemicelluloses
1160C-O-C stretching vibration of hemicelluloses
1380CH3 and CH deformation
1460C-H deformation of lignin, and C-H2 bending of hemicellulose
1540N-H bending vibration, amide II
1657C=O, amide I
1723Acetyl or uronic ester group of hemicellulose
2700Bending OH overtone vibrations for tannins
2853Asymmetric and symmetric CH2 and CH3 of epoxy resin
3290Vibration of OH group of cellulose
Table 3. Concentration and extraction efficiency of hemicellulose, lignin, and cellulose (HPLC analysis).
Table 3. Concentration and extraction efficiency of hemicellulose, lignin, and cellulose (HPLC analysis).
PeakCompound NameMolecular FormulaConcentration (mg/L)Extraction Rate
AHemicelluloseC5H8O48245.254.9%
BLignin(C31H34O11)n10,435.469.5%
CCellulose(C6H10O5)n13,245.488.3%
Table 4. Comparison of hemicellulose, lignin, and cellulose extraction rates using different methods.
Table 4. Comparison of hemicellulose, lignin, and cellulose extraction rates using different methods.
Study and SampleHemicellulose Extraction Rate (%)Lignin Extraction Rate (%)Cellulose Extraction Rate (%)Extraction MethodRef.
This study (BSG)54.9%69.5%88.3%Alkaline Pretreatment (5% NaOH) + Ultrasonication (1000 Hz, 1 h) + Ethanol Precipitation
Pal et al. (Rice Straw) 60.0% NH3 in Water-THF[70]
A. Das et al., Optimized Ultrasound-Assisted (Bamboo) 65.8% Ultrasound-Assisted Extraction[71]
N. Wang., Hydrothermal Pretreatment (Bagasse)32.6% 81.2%Hydrothermal Pretreatment[72]
Table 5. Soluble fatty acid content (mg/100 g DW) determined by GC-FID by boiling-point-temperature fractions obtained from BSG extracted from conventional solvent extraction.
Table 5. Soluble fatty acid content (mg/100 g DW) determined by GC-FID by boiling-point-temperature fractions obtained from BSG extracted from conventional solvent extraction.
PeakCompound NameMolecular FormulaConcentration (mg/L)
AOleanolic acidC30H48O30.243
BOleic acidC18H34O20.057
CLinoleic acid C18H32O20.547
DArachidic acidC20H40O20.1737
Table 6. Soluble bioactive compounds (mg/L) determined by HPLC using polarity temperature fractions obtained from BSG extracts through conventional extraction.
Table 6. Soluble bioactive compounds (mg/L) determined by HPLC using polarity temperature fractions obtained from BSG extracts through conventional extraction.
PeakCompound NameConcentration (mg/L)Extraction Rate
AAscorbic acid1.5923
BGallic acid2.314
CCatechol2.739
DEllagic acid162.88
EAcetylsalicylic acid0.63
FVanillin590.168845.8%
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Chu, H.-Y.I.; Miri, T.; Onyeaka, H. Valorization of Bioactive Compounds Extracted from Brewer’s Spent Grain (BSG) for Sustainable Food Waste Recycling. Sustainability 2025, 17, 2477. https://doi.org/10.3390/su17062477

AMA Style

Chu H-YI, Miri T, Onyeaka H. Valorization of Bioactive Compounds Extracted from Brewer’s Spent Grain (BSG) for Sustainable Food Waste Recycling. Sustainability. 2025; 17(6):2477. https://doi.org/10.3390/su17062477

Chicago/Turabian Style

Chu, Hao-Yu Ivory, Taghi Miri, and Helen Onyeaka. 2025. "Valorization of Bioactive Compounds Extracted from Brewer’s Spent Grain (BSG) for Sustainable Food Waste Recycling" Sustainability 17, no. 6: 2477. https://doi.org/10.3390/su17062477

APA Style

Chu, H.-Y. I., Miri, T., & Onyeaka, H. (2025). Valorization of Bioactive Compounds Extracted from Brewer’s Spent Grain (BSG) for Sustainable Food Waste Recycling. Sustainability, 17(6), 2477. https://doi.org/10.3390/su17062477

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