Next Article in Journal
Enhanced Antioxidant Properties of Saccharomyces-Fermented Defatted Tenebrio molitor Larvae Extract: A Sustainable Alternative Protein Source
Previous Article in Journal
Integrated Process Combining High-Temperature Fermentation and Extractive Ethanol Removal via CO2 Stripping
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Fermentation
Volume 11
Issue 5
10.3390/fermentation11050271
fermentation-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Improving Nutrition Facts of Cassava and Soybean Residue Through Solid-State Fermentation by Pleurotus ostreatus Mycelium: A Pathway to Safety Animal Feed Production

by
Nguyen Thi Bich Hang
and
Chi Cuong Doan
*
Faculty of Biology, Agriculture and Environmental Science, University of Science and Education—The University of Danang, Danang 550000, Vietnam
*
Author to whom correspondence should be addressed.
Fermentation 2025, 11(5), 271; https://doi.org/10.3390/fermentation11050271
Submission received: 15 March 2025 / Revised: 7 April 2025 / Accepted: 24 April 2025 / Published: 9 May 2025
Browse Figures
Versions Notes

Abstract

:
The overwhelming amount of cassava residues and okara are a foremost challenge for the food processing industry environmental loading. The purpose of this article is to utilize Pleurotus ostreatus mycelium to ferment solid cassava and soybean residue, resulting in mycelial biomass with nutritional values and promising prebiotic activities from fermented waste sources. By blending a ratio of 80% cassava and 20% soybean residues, the mycelium spread rapidly after 3 days of culture, from 1.73 mm on the first day to 13.32 mm on the third day, and completely covered the surface after 9 days of culture (120 mm). Using the solid-state fermentation (SSF) method allowed us to improve the content of substances isolated from mycelium biomass, where polysaccharide content rose by 2.1 times to 3.44 mg/g, and the protein content increased by 1.84 times over the initial substrate. The prebiotic activity of extracted PS was greatest in P. acidilactici NBD8 (1.58); for L. pentosus NH1, L. argentoraten NH15, and L. plantarum WCFS1 strains, the indices were 0.11, 0.17, and 0.3, respectively. The SSF process with P. ostreatus mycelium has the potential to be an effective method for improving the nutrition and digestibility of soybean and cassava residues for application in the production of nature-derived animal feed, as well as contributing to fully utilized agricultural residue, agriculture’s circular economy, reducing environmental issues, and achieving the net-zero carbon emissions target by 2050, as the Vietnam government committed to achieving during the COP26 World Leaders’ Summit in 2021.

1. Introduction

Solid-state fermentation (SSF) refers to a fermentation process in which microorganisms grow on a solid substrate that lacks or has limited free water, and complex materials are transformed into simpler ones [1,2,3]. It is considered one of the technologies for conversion of agricultural by-products into valuable products for nutrition and human health [4,5], animal feed [6,7,8], biofuel [9,10,11,12], and bio-protection for grain crops [13,14,15]. SSF regularly employs agricultural and agro-industrial by-products as low-economic-value raw materials rather than discarding them as an environmental concern; these materials are used as substrates in the fermentation process [16,17]. Various agricultural substrates have been successfully used in SSF to produce ligninolytic enzymes, which decompose lignin, a major contributor to the total carbon of agro-industrial wastes, and produce polycyclic aromatic hydrocarbon compounds that can inhibit DNA synthesis and induce cancerous tumors in the liver, lungs, larynx, and cervix in animals and humans [18,19]. Pleurotus ostreatus is one of the significant edible mushrooms, capable of decomposing lignocellulose without the need for chemical or biological preparation due to its enzymatic complex system, which contains phenol oxidases and peroxidases [1,20].
Compared to SSF, submerged fermentation (SMF) is better for biomass production and is suitable for a wide range of microorganisms, including bacteria and yeasts, and generally yields a more homogeneous product, simplifying downstream processing. However, SMF generates substantial liquid waste, necessitating effective waste management strategies, and may involve higher costs for substrates, as it often relies on refined nutrients. Hence, SSF is often favored over SMF for processing agro-residues due to cost-effectiveness, which agro-industrial residues serve as inexpensive and abundant substrates in SSF, reducing production costs and adding value to these by-products; environmental sustainability, SSF being lower in water and energy requirements, coupled with requiring minimal liquid waste generation, make it an environmentally friendly approach for agro-residue valorization; and enhanced product yields, being that the solid substrates used in SSF provide a natural habitat for filamentous fungi, leading to efficient production of the desired metabolites [21].
In Vietnam, the cassava starch and tofu processing and soybean milk production industries are large-scale sectors that generate significant amounts of residue. According to a report by the Institute of Vietnam Agricultural Environment, approximately 10.3 million tons of cassava residues and 1.9 million tons of soybean residue and by-products are generated annually [22]. This source is often only partially used in its fresh form as feed for livestock or solid compost, with the majority not being utilized, leading to environmental pollution and the wastage of this recyclable resource. Soybean residue (also called okara) and cassava residues retain a substantial amount of fiber and nutrients, making them suitable substrates for the growth of edible and medicinal mushrooms. Wet okara contains about 6% fat, 8.08% protein, 12.01% carbohydrates, 5% dietary fiber, 1% ash, and 32.05% total solid, meanwhile, these compositions in dried okara were 12.06, 34.15, 48.9, 33, 2.05, and 95.04%, respectively [23,24,25]. In other studies, it was reported that okara had an amount of 10% lipid, 25% protein, and 50% fiber [26,27,28]. As for cassava residue, Yimin (2015) announced that crude protein and neutral detergent fiber content were 1.30–16.41% and 25.4–52.9% on a dry matter basis, respectively [29]. Parts of the cassava plant contain different concentrations of lysine, ranging from 3.9 g/100 g in leaves to 7.2 g/100 g dry weight in roots, and soluble and insoluble dietary fiber contents in cassava pulp by-products reached 2.29% and 15.07%, respectively [30,31]. In another study, it was reported that cassava residue had high organic content, including approximately 2.19% crude protein, 60.37% starch, 0.52% crude lipid, total minerals at 2.01%, and 21.01% fiber [32].
As for recent achievements around the world, Zhu (2020) designed, synthesized, and characterized superabsorbent hydrogels that had high capacities of water absorbency, holding, and retention through graft copolymerization of soybean residue with acrylic acid and acrylamide [33]. Sabater (2020) made a minireview to introduce new ways of valorization of vegetable food waste and by-products through fermentation processes to improve nutritional value or to produce biologically active compounds from those waste and by-products [34]. Oktaviani (2021) applied bioconversion of cassava peel residue into yeasts to produce cell wall mannoprotein as an antioxidant [35]. Suriyapha (2022) delved into how to make bioconversion of agro-industrial residues as a protein source supplementation for cows [36]. In that study, the authors tried to compare the effects of Holstein Thai crossbreed cows with citric waste and fermented yeast waste on absorption, digestibility, fermentation activity in the stomach of ruminants, blood metabolites, cognation of purine, milk production, and economical efficiency of tropical lactating cows [36]. Verardi (2023) reviewed research on agricultural residue recovery through fermentation technology, analyzed the key steps in the agro-residue bioconversion process, and the most common microorganisms employed in this procedure [37]. Bala (2023) addressed pathways to convert agro-residues into valuable bioproducts and bioactive compounds, as well as their applications [38]. Blasi (2023) reviewed the valorization methods employed for biotransformation of lignocellulosic agricultural waste into economically and environmentally valuable products, such as the production of biofuels, and the synthesis of platform chemicals; the creation of materials that is composed entirely of matter taken from living microorganisms; and the production of extracellular fungal enzymes, organic acids, and compounds that have a biological activity [39]. Cruz (2021) and Adnane (2024) provided a thorough examination or evaluation of anaerobic co-digestion technology as a biochemical recovery pathway of cassava residue and other agricultural residues for the production biogas that fulfills the global target of renewable energy [40,41].
It can be seen from the literature that Oktaviani (2021) utilized cassava peel residue as a substrate for yeast cultivation to extract antioxidant-rich mannoproteins [35]. However, this study focused on yeast fermentation rather than fungal mycelium, and its main goal was to obtain functional compounds, not to enhance the feed or food value of the cassava waste. Cruz (2021) and Adnane (2024) explored cassava residue for biogas production using anaerobic digestion, aiming at energy recovery rather than nutritional enhancement [40,41]. Zhu (2020) converted soybean residues into hydrogel materials via chemical modification (graft polymerization) for non-food, non-feed applications [33]. There have been a few studies using soybean meal or okara in fungal fermentation, primarily focusing on enzyme production or isoflavone enrichment, but these often used submerged fermentation and not P. ostreatus. Suriyapha (2022) used yeast-fermented agro-industrial waste as protein supplementation for cows, but did not involve Pleurotus and focused on animal trials rather than primary substrate improvement [36]. Most of these works focus either on a single substrate or on fungal species such as Trichoderma or Aspergillus, not P. ostreatus on cassava–soybean mixed substrates.
In this study, we proposed a method for bioconversion of cassava and soybean residues to derive valuable bio-substances, such as polysaccharide (PS) and protein by the purple P. ostreatus mycelium, through SSF; in addition, the prebiotic activity of PS isolated from fermented substrate was also evaluated. The combination of cassava and soybean residues is novel. Most studies focus on one or the other, but combining them may provide a more balanced C:N ratio, enhancing fungal growth and nutritional outcomes. While Pleurotus has been studied in SSF, there is little documentation of its use on cassava–soybean mixtures for nutritional upgrading, particularly focusing on enhancing protein content, fiber reduction, and digestibility. Unlike studies targeting bioenergy, material synthesis, or specific compound extraction, this research is directly aimed at improving the overall nutrition profile of residues for potential use as animal feed or functional food ingredients. Many works apply submerged fermentation; SSF is more industrially and environmentally friendly for agro-residues and aligns with sustainable practices, especially in rural or resource-limited settings. The present study provides a practical perspective often missing from purely lab-scale or theoretical studies.
P. ostreatus is one of the most popular mushrooms cultivated in Vietnam due to the eating culture and humid tropical monsoon conditions. It contains a variety of nutrients and bioactive substances such as proteins, fibers, lipids, carbohydrates, minerals, vitamins, and bioactive compounds such as PS, phenols, and flavonoids [42]. The applications of PS obtained from mushroom mycelium mainly focus on antioxidant activities, anti-tumor effects, immune modulation, stimulation of macrophage functions, and lung cell protection [43]. The biologically active PS in the purple oyster mushroom was reported to occur from the mycelial growth stage without the need for the fruiting body to fully develop [44]. Thus, the use of SSF to harvest mycelial biomass may shorten the cultivation cycle, easily control the cultivation conditions on an industrial scale to obtain a large amount of mycelial biomass, opening prospects for the development of diverse substrate sources for producing mushroom fiber rich in polysaccharides, both of high medicinal value and nutritional value for use in the livestock industry, and reduce environmental issues caused by agricultural residue.

2. Materials and Methods

2.1. Substrate Sources and Baterial Strains

Fresh cassava residue was collected from a tapioca starch processing factory in Quang Nam province (Q86F+498, ĐT611, Que Cuong commune, Que Son district, Quang Nam, Vietnam). Fresh soybean residue was sampled from Hoa Khanh market (Dong Ke Street, Hoa Khanh Bac town, Lien Chieu district, Danang city, Vietnam). These residues then were sun-dried for 3 days and ground into fine powder by a miller (SM-450L, MRC Laboratory Instruments), each 150 g for 3 min. The purple oyster mushroom (P. ostreatus) was provided by the Laboratory of Biology—Environment, University of Science and Education—The University of Danang (459 Ton Duc Thang Street, Lien Chieu district, Danang, Vietnam).
Probiotic strains, Lactiplantibacillus plantarum WCFS1, Lactiplantibacillus pentosus NH1, Lactiplantibacillus argentoraten NH15, Pediococcus acidilactici NBD8, and the pathogenic strain Escherichia coli ATCC 85922 were used to assess the prebiotic activity of polysaccharides fermented from mushroom mycelia. Commercial prebiotics named INFOGOS (each bag contained equal proportions of inulin, galacto-oligosaccharides (GOS), and fructo-oligosaccharides (FOS)) were distributed by the Southeast Asia Pharmaceutical and Trading company (46 Lot 5, Den Lu 2 Urban Area, Hoang Van Thu Ward, Ha Noi, Ha Noi Vietnam).

2.2. Preparation of P. ostreatus Colonies in the Liquid Medium

The potato dextrose broth (PDB+) medium was prepared by boiling 200 g finely diced potatoes in 500 mL of distilled water until thoroughly cooked (about 60 min); filter through cheesecloth, then supplement 20 g of D-glucose, 2 g of peptone, and 2 g of yeast extract and add distilled water to 1000 mL. A total of 100 mL of PDB+ medium was dispensed into 250 mL Erlenmeyer flasks and then autoclaved (HVA-110, Hirayama Manufacturing Corporation, Saitama, Japan) at 121 °C for 30 min. After cooling down, a uniform piece of P. ostreatus mycelium (approximately 1 cm2) was inoculated into each Erlenmeyer flask from a first-generation culture tube to proceed with the shaker equipment (SHO-2D, Daihan Scientific, Gangwon, Republic of Korea) at a speed of 150 rpm at a temperature range of 25 to 28 °C for 7 days. The liquid culture medium then contained P. ostreatus colonies, which were used for the SSF experiment of cassava and soybean residue.

2.3. Solid-State Fermentation of Cassava and Soybean Residue with P. ostreatus Mycelium

The experiment was conducted to evaluate the growth of the P. ostreatus mycelium on various experimental treatments containing a mixture of soybean and cassava residues as presented in Table 1.
In total, 100 g of the substrate in each treatment was transferred into polypropylene plastic boxes (with an upper-diameter of 12 cm and bottom-diameter of 10 cm) to autoclave (HVA-110, Hirayama Manufacturing Corporation, Japan) at 121 °C, 1 atm, for 20 min. After cooling down, 5 mL of the solution of colonies containing was taken by a modified micropipette tip (Finnpipette, Thermo Scientific, Vantaa, Finland) to inoculate into each box at the center as a single dose. The cultivation phase of P. ostreatus mycelium was maintained at a temperature range of 25–28 °C, and subsequently, the spread rate and morphological characteristics of the mycelium were observed and evaluated after 1, 3, 5, 7, and 9 days of cultivation, and the days when mycelium first and last recorded covered on the surface of the substrate among treatments. The purpose of this experiment is to select the most appropriate treatment for further tests, including the nutrient profile of fermented substrate and prebiotic activities of extracted PS.

2.4. Extraction and Quantification of PS

The entire fermented substrate of the selected treatment of the above experiment (Section 2.2) was dried to a constant weight (about 48 h) at 55 °C (Memmert UN110, Schwabach, Germany). We took 25 g of dry, finely ground fermented substrate obtained after grinding with a miller (SM-450 L, MRC Laboratory Instruments, Harlow, UK) to mix it with 375 mL of distilled water, followed by incubation at 70 °C for 3 h. The mixture was then vigorously shaken and filtered through Whatman filter paper, and the filtrate was precipitated using 96% ethanol in a 1:4 ratio for 12–24 h at 4 °C. Subsequently, the mixture was centrifuged at 10,000 rpm for 10 min. The supernatant was discarded, and the sediment was dissolved in 1 M NaOH at 60 °C for one hour to obtain a solution for PS analysis. The quantification of PS was conducted using the phenol–sulfuric acid method [45]. When PS reacts with concentrated sulfuric acid, it dehydrates and produces furfural derivatives. These derivatives then react with phenol, resulting in a colored compound that can be measured spectrophotometrically. A 2 mL, PS solution is mixed with 1 mL of 5% aqueous phenol in a test tube, followed by the rapid addition of 5 mL concentrated sulfuric acid. After standing for 10 min, the mixture is vortexed for 30 s and left in a room-temperature water bath for 20 min to develop color. Absorbance at 490 nm is then measured using a spectrophotometer. Reference samples are prepared the same way, replacing the PS solution with distilled water. The phenol was redistilled and the 5% solution was prepared fresh before use.

2.5. Assessment of the Impact of PS on the Growth of Gut Probiotics

The experimental medium used to evaluate the impact of extracted PS on the growth of beneficial gut bacteria (probiotics) was prepared as follows: GF (glucose free) is de-Man, Rogosa, and Sharpe (MRS) broth medium that glucose eliminated; PS is GF medium supplemented with 1 g/L PS; Pre (prebiotic) is GF medium supplemented with 1 g/L commercial prebiotic (named INFOGOS, used as a control); Glc (glucose) is GF medium supplemented with 1 g/L glucose; GlPs (glucose polysaccharide) is Glc medium supplemented with 1 g/L PS; and GlPre (glucose prebiotic) is Glc medium supplemented with 1 g/L commercial prebiotic. These media were filled into 50 mL polypropylene falcon tubes (Thermo Fisher Scientific Inc., Waltham, MA, USA). The probiotic strains (Section 2.1) were then inoculated into those media-containing tubes. After that, the falcon lids were tightly closed, and a layer of paraffin was wrapped around the lid to prevent air penetrating into the culture medium. These bacterial strains then were incubated in the incubator (Memmert UN110, Germany) at 37 °C for 48 h. Subsequently, the cell density of the liquid media was determined by measuring the optical density at a wavelength of 600 nm at time points of 0 h, after 24 h, and 48 h [46].

2.6. Calculation of Prebiotic Index

The prebiotic activity of PS extracted from the mycelium after the SSF of cassava and soybean residues was evaluated through the prebiotic index (PI). The beneficial gut bacterial strains were cultured in GF, PS, Pre, and Glc media. The strain E. coli ATCC 85922 was cultured in M9 medium [47] with glucose eliminated, and supplemented with 1 g/L PS, 1 g/L glucose, and 1 g/L commercial prebiotic. All the bacterial strains were incubated at 37 °C for 24 h. The optical density of the liquid samples at a wavelength of 600 nm (OD600) was measured at 0 h and 24 h to determine the biomass accumulation capacity. The PI was calculated using the following formula [48].
P I = P p 24 − P p 0 − P G F 24 − P G F 0 P G 24 − P G 0 − P G F 24 − P G F 0 − E p 24 − E p 0 − E G F 24 − E G F 0 E G 24 − E G 0 − E G F 24 − E G F 0
where P p 0 , P p 24 , P G F 0 ,   P G F 24 , and P G 0 , P G 24 were OD600 values of beneficial gut bacteria cultured in Pre; GF; and Glc medium at 0 h and 24 h. E p 0 , E p 24 , E G 0 , E G 24 , and E G F 0 , E G F 24 were OD600 values of E. coli cultured in Pre; Glc; and GF medium at 0 h and 24 h.

2.7. Assessment of Mycelial Biomass Quality

The substrate mixture (cassava and soybean residues) in selected treatment (experiment in Section 2.3) will be analyzed for composition before (as raw material) and after fermentation (fermented substrate). The protein content was determined according to ISO 5983-2: 2009 for livestock feed—this standard specifies the method for determining nitrogen content and calculating crude protein content using the Kjeldahl method [49]. Lipid content was analyzed in accordance with ISO 6492:1999 for livestock feed—this specifies the determination of fat content by hexane extraction [50]. The crude ash content was analyzed according to ISO 5984:2022 for livestock feed [51].

2.8. Data Analysis

Each experimental formula was replicated three times, with each replication consisting of five identical treatments. Descriptive statistics were used to determine mean values and standard deviations. The treatments were compared using one-way analysis of variance (ANOVA) and the Tukey HSD test for a significance level of 95%.

3. Results and Discussion

3.1. Impact of the Cultivation Substrate on the Growth of P. ostreatus Mycelium

Agricultural residue typically contains a variety of substances and numerous nutrients remaining after the processing phase. These provide a rich source of raw materials for SSF to produce mycelial biomass from various types of mushrooms. The nutrient content within the substrate significantly influences the growth and development of the mushroom mycelium during SSF. Changes in the diameter of the P. ostreatus mycelium on the surface of the substrate in the treatments during the SSF process are depicted in Table 2 and Figure 1.
The findings indicate that the mixing ratio between cassava and soybean residues significantly affects the spread rate and morphology of the mushroom mycelium. Treatments with a higher ratio of cassava residue showed rapid mycelium spread and completed occupying of the whole substrate surface quicker than those with a higher ratio of soybean residue. In treatments CT1, CT2, and CT3, the mycelium spread rapidly and covered the surface of the medium after 9 days of cultivation (120 mm). In CT4 and CT5, the spread rate was slower, the mycelium covering approximately 90% and 70.24% of the substrate surface after 9 days (108.07 mm and 84.29 mm, respectively). CT1 (100% cassava residue) showed the fastest spread rate, with the mycelium covering 92% of the surface by the seventh day (110.62 mm), followed by CT2 and CT3 with about 70% (83.18 mm and 82.51 mm, respectively) (Table 2).
Nair (2012) reported that the high fiber and carbohydrates content (14.88 g/100 g and 63.85 g/100 g dry weight), good thermal stability, and high crystallinity in cassava residue might make the substrate more porous, allowing the mycelium to develop and spread more quickly [52]. This can explain the early surface coverage of mycelium observed in CT1, CT2, and CT3, because soybean residue contains mostly crude fiber composed of cellulose, hemicellulose, and lignin, about 25% protein, 10–15% oil, but little starch or simple carbohydrates [53]. Hence, a high proportion of soybean residue in treatments will result in increasing compaction and reduce the porosity of the substrate, while the diversity and richness in nutrients remaining in the soybean residue often led to slower mycelium development due to a lack of oxygen for respiration and decomposition of complex compounds. This demonstrated the slower mycelium spread on the substrate in treatments CT4 and CT5 where soybean residue occupied 30% and 40%, respectively.
Sensory evaluation of the mycelium thickness on the substrate surface revealed distinct differences among the treatments. P. ostreatus mycelium in CT3, CT4, and CT5 had the highest density, was fluffy, and was evenly white, while CT1 and CT2 had a lower density. This might be due to the rich and higher nutrient content in soybean residue compared to those in cassava residue [30,53] with high levels of nitrogen and vitamins, facilitating the growth and biomass accumulation of the mycelium during fermentation. The productivity and quality of the mycelium depend on the nutritional status from the substrate source, such as the C/N ratio, vitamins, plant hormones, and trace and macro minerals [54].
After 30 days of cultivation, the mycelium covered the entire substrate in all treatments (Figure 1). In CT4 and CT5, although the mycelium covered the surface of the substrate, the bottom of the boxes still had sparse mycelium, and some boxes showed no further mycelium spread upon continued cultivation. In CT1 and CT2, the low nutrient content might have led to low mycelial biomass and the mycelium drying out and dying over time. In contrast, for CT3, the mycelium developed fully and appeared fluffy and white across the cultivation plastic boxes when the SSF period was extended, showing signs of fruiting body development on the substrate surface. Therefore, the 80% cassava + 20% soybean residue mix in CT3 was selected for further experiments.

3.2. Nutrients Profile of Fermented Substrate After SSF by P. ostreatus Mycelium

As presented in Figure 2, the PS content in the substrate after SSF increased approximately 2.12 times compared to the unfermented raw substrate (from 1.62 mg/100 g to 3.44 mg/100 g). The increase in PS content could be attributed to the mycelium utilizing a rich carbon source, including compounds such as starch, cellulose, and lignocellulose, for growth and accumulating intracellular polysaccharides from the fungal fibers and unutilized crude polysaccharides following lignocellulose hydrolysis. The rise in PS content after SSF by the mushroom mycelium was also demonstrated in the study by Lu (2023) when conducted on substrates of corn stalks and xyloma sawdust (a plant belonging to the Willow family, Salicaceae) using Shiitake (Lentinula edodes) and oyster mushroom (P. ostreatus) mycelium [55].
Protein, lipid, carbohydrate, and total ash content are also important quality indicators of the product after SSF. Substrates from agricultural by-products typically contain relatively low nutrient levels. However, after fermentation with mushroom mycelium, the nutritional composition was significantly improved, especially in terms of protein content [56]. In this study, there was a significant increase in protein content in the substrate after SSF of about 1.84 times (from 4.29 mg/100 g to 7.91 mg/100 g). This increase might be due to the high protein content (28.85%) of the oyster mushroom [57,58], thus the increase in mycelium biomass during growth led to an increase in accumulated protein content. The total lipid content in the substrate before and after fermentation did not change significantly (0.82–0.83 mg/100 g). Meanwhile, the starch content after SSF decreased by about 41.39% (from 55.66 mg/100 g to 32.62 mg/100 g). Starch usually constitutes a high proportion in the raw substrate composition. During fermentation, the mushroom mycelium used starch as a carbon source for growth and transformation into other compounds, leading to a decrease in starch content in the substrate after SSF [59]. The total ash content in the substrate after fermentation increased by 1.86 times (from 1.69 mg/100 g to 3.14 mg/100 g). The increase in total ash content could be due to the presence of minerals in the second-stage fermentation broth of the oyster mushroom when inoculating and some minerals from the water added to the substrate to maintain moisture.

3.3. Prebiotic Activity of PS After Extraction

Prebiotics, as defined by the International Scientific Association for Probiotics and Prebiotics (ISAPP), are non-digestible food components that selectively feed beneficial microorganisms [60]. Prebiotics added to the diet will not be digested and absorbed by poultry. However, they can play a crucial role in selectively promoting the growth of certain beneficial bacteria, improving the gut microbiome, and enhancing the absorption and utilization of nutrients [61]. In the present study, we evaluated the prebiotic activity of PS extracted from the substrate after SSF with purple oyster mushroom mycelium by assessing the ability of probiotic strains to utilize PS as a nutritional source and evaluating through the prebiotic activity index.

3.3.1. The Impact of PS on the Growth of Beneficial Gut Probiotics

The prebiotic activity of PS is due to the selective metabolic capability of the probiotics (beneficial bacteria), thereby stimulating their growth [62]. The ability of probiotic strains to metabolize carbohydrates similarly to glucose is a prerequisite for assessing the prebiotic activity of a carbohydrate. In this study, four bacterial strains, P. acidilactici NBD8, L. pentosus NH1, L. argentoraten NH15, and L. plantarum WCFS1 were used to evaluate the ability to use PS extracted from the mixture of substrate and mycelium after SSF.
The three Lactiplantibacillus strains showed the highest growth rate in the medium with glucose as the carbon source (Figure 3). The control glucose medium (Glc) allowed mycelium development easily because glucose is a common metabolized sugar for living cells. However, P. acidilactici NBD8 grew better in the PS and Pre medium.
In medium supplemented with PS, all four bacterial strains showed higher growth than in those without an added carbon source. Thus, P. acidilactici NBD8, L. pentosus NH1, L. argentoraten NH15, and L. plantarum WCFS1 could use PS extracted from the substrate after SSF as a carbon source. However, in the PS medium, the accumulation of mycelial biomass was lower than in the Pre medium; this could be because the PS extracted from the substrate after SSF is crude PS not yet purified and contains some insoluble impurities, whereas commercial prebiotics are purified PS proven to selectively stimulate the growth of beneficial bacteria species. However, P. acidilactici NBD8 showed significant growth within 24 h. This may be due to each probiotic strain producing different amounts of hydrolyzing enzymes and having varying rates of carbon source degradation for nutrition; hence, their growth rates differ. This finding aligns with the study conducted by Phirom-On (2021), where L. plantarum SKKL1, L. plantarum TISTR 2075, and L. casei TISTR 1463 could use cello-dextrin extracted from banana peels as a carbon source alternative to glucose for growth [46].
Both GlPs and GlPre mediums strongly stimulated the growth of probiotics. For P. acidilactici NBD8 cultured on GlPs medium, growth was better than on GlPre medium. After 48 h of cultivation in GlPre medium, bacteria entered a degradation phase and cells were decomposed, so the OD600 value decreased, while in GlPs medium, the OD600 value continued to increase.
For the three beneficial probiotic strains L. pentosus NH1, L. argentoraten NH15, and L. plantarum WCFS1, after 24 h of cultivation, the OD600 value in GlPs medium was lower than those in GlPre medium. After 48 h of cultivation, the OD600 value in both mediums continued to increase, especially L. argentoraten cultured in GlPs medium, which had a higher OD600 value than in GlPre medium. This may be because PS extracted from mycelium contains more complex structural components than commercial prebiotics, so the probiotic strains in the adaptation phase could not immediately use them for growth. They had to accumulate a certain biomass and produce enough extracellular enzymes to degrade and utilize these prebiotics, leading to a longer time required to achieve equivalent biomass levels. This result was similar to the findings of Nguyen Thi Bich Hang (2023) when supplemented 10 mg/mL PS was extracted from Cordyceps militaris mycelium to evaluate the stimulatory effect on the growth of L. plantarum strain [63].
Aida (2009) also emphasized that the mycelium of many mushroom species contains PS with prebiotic activity (such as chitin, hemicelluloses, β and α–glucan, mannan, xylan, and galactan) [64]. α–(1,3)–glucan, one of the PS extracted from the cell walls of two species P. ostreatus and P. eryngii, has been shown to stimulate the growth of bifidobacterium and Lactobacillus [65].

3.3.2. Prebiotic Index (PI)

According to Huebner (2007), the activity of a prebiotic is defined as the ability of a specific substrate, typically a prebiotic substance, to support the growth of beneficial bacteria in the gut compared to other bacteria [66]. To evaluate the activity of a prebiotic, it is often compared to the growth on a non-prebiotic substrate, usually glucose. Therefore, a carbohydrate exhibits a positive prebiotic activity index if it is metabolized similarly to glucose by probiotic strains, and is selectively metabolized by probiotics rather than by other gut bacteria [66].
The OD600 value measured after 24 h of culture clearly demonstrated that the culture medium influenced the growth of both beneficial and harmful bacteria. All strains grew slowly in MRS medium without carbon (GF), with OD600 values ranging from 0.06 to 0.26, but increased faster in medium supplemented with glucose and commercial prebiotics with OD600 values ranging from 0.29 to 1.13 for the Glc medium and 0.25 to 0.64 for the Pre medium. Notably, on medium supplemented with PS, growth stimulation was greater for probiotic strains, particularly for P. acidilactici NBD8 (OD600 = 0.71) than for E. coli ATCC 85922 (OD600 = 0.09) (Figure 4).
In treatments using PS as a carbon source, all probiotic strains showed positive prebiotic indices (ranging from 0.11 to 1.58). The highest prebiotic index was observed in the strain P. acidilactici NBD8 (1.58); the PI values of the other strains L. pentosus NH1, L. argentoraten NH15, and L. plantarum WCFS1 were 0.11, 0.17, and 0.30, respectively (Figure 5). The lower PI in the three Lactiplantibacillus strains could be due to their poorer growth in the medium supplemented with PS compared to the one supplemented with glucose. In the Pre medium, although the growth stimulation effect on the probiotic strains was higher than in the PS medium, the three Lactiplantibacillus strains showed negative prebiotic indices (–0.18; –0.32; and –0.41), and only the strain P. acidilactici NBD8 showed a positive PI (0.28). The reason for this negative value could be that the commercial prebiotic stimulated the growth of harmful microorganisms (E. coli ATCC 85922) as much as glucose did. According to Huebner (2007), strains L. plantarum 12006 and L. acidophilus 33200 showed a negative PI when cultured on all prebiotics, except for purified GOS [66].
This study also showed that the same type of PS can have different prebiotic indices in different bacterial strains. This can be explained by the fact that different microbial strains have different metabolic capabilities, leading to variations in prebiotic indices. Probiotic strains need specific hydrolytic enzyme systems to utilize prebiotics. Therefore, the genes encoding these metabolic systems may or may not be present in different strains, leading to different prebiotic activity indices. The hydrolytic enzyme systems play a crucial role in the ability of probiotic strains to use prebiotics. Each probiotic strain may have genetic variations and permutations in these systems, which can create diversity in their ability to utilize and metabolize prebiotics. This causes variations in prebiotic indices [67].
The positive prebiotic indices indicate that the level of PS extracted from the substrate after SSF with mycelium selectively promoted the growth of the strains P. acidilactici NBD8, L. pentosus NH1, L. argentoraten NH15, and L. plantarum WCFS1. Meanwhile, the E. coli ATCC 85922 strain did not effectively utilize this PS as a carbon source for growth.

4. Conclusions

The blending ratio in the experimental formula containing 80% cassava and 20% soybean residues provided the most favorable conditions for the growth of the P. ostreatus mycelium, showing a rapid expansion after 3 days of cultivation (from 1.73 mm to 13.32 mm) and covering the entire plate surface after 9 days of cultivation (120 mm). The polysaccharide content extracted from the substrate after SSF reached 3.44 mg/g, increased by 2.1 times, with protein and mineral content increasing about 1.84 times compared to the initial substrate. The highest prebiotic index was observed in the strain P. acidilactici NBD8 (1.58); whereas, in the strains L. pentosus NH1, L. argentoraten NH15, and L. plantarum WCFS1, the indices were 0.11, 0.17, and 0.30, respectively. The SSF process using P. ostreatus mycelium holds potential as an effective method to enhance the nutrition and digestibility of soybean and cassava residues for application in the production of natural-origin animal feeds, and also holds potential for contributing to the circular economy in agriculture by fully utilizing by-products of the agricultural production industry.

Author Contributions

Conceptualization, software, validation, formal analysis, investigation, writing—review and editing: C.C.D., methodology, visualization, project administration, writing—original draft preparation: N.T.B.H. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by VIETNAM MINISTRY OF EDUCATION AND TRAINING, grant number B2024.DNA.11.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data and material of this study are available on request.

Acknowledgments

The authors thank Bui Duc Thang and Truong Cong Phat for technical support at the Mushroom Laboratory, Faculty of Biology and Environmental Sciences—University of Science and Education—The University of Danang.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

References

  1. Arvanitoyannis, I.S.; Kassaveti, A.; Ladas, D. Chapter 6. Food Waste Treatment Methodologies. In Waste Management for the Food Industries; Arvanitoyannis, I.S., Ed.; Academic Press: Amsterdam, The Netherlands, 2008; pp. 345–410. ISBN 978-0-12-373654-3. [Google Scholar]
  2. Parmar, A.B.; Patel, V.; Usadadia, S.; Rathwa, S.; Prajapati, D. A Solid State Fermentation, Its Role in Animal Nutrition: A Review. Int. J. Chem. Stud. 2019, 7, 4626–4633. [Google Scholar]
  3. Mitchell, D.A.; de Lima Luz, L.F.; Krieger, N.; Berovič, M. 2.25—Bioreactors for Solid-State Fermentation. In Comprehensive Biotechnology; Moo-Young, M., Ed.; Pergamon Press: Oxford, UK, 2011; pp. 347–360. ISBN 978-0-08-088504-9. [Google Scholar]
  4. Feng, X.; Ng, K.; Ajlouni, S.; Zhang, P.; Fang, Z. Effect of Solid-State Fermentation on Plant- Sourced Proteins: A Review Effect of Solid-State Fermentation on Plant-Sourced Proteins: A Review. Food Rev. Int. 2023, 40, 2580–2617. [Google Scholar] [CrossRef]
  5. Cano y Postigo, L.O.; Jacobo-Velázquez, D.A.; Guajardo-Flores, D.; Garcia Amezquita, L.E.; García-Cayuela, T. Solid-State Fermentation for Enhancing the Nutraceutical Content of Agrifood by-Products: Recent Advances and Its Industrial Feasibility. Food Biosci. 2021, 41, 100926. [Google Scholar] [CrossRef]
  6. Yang, L.; Zeng, X.; Qiao, S. Advances in Research on Solid-State Fermented Feed and Its Utilization: The Pioneer of Private Customization for Intestinal Microorganisms. Anim. Nutr. 2021, 7, 905–916. [Google Scholar] [CrossRef]
  7. Vandenberghe, L.P.S.; Pandey, A.; Carvalho, J.C.; Letti, L.A.J.; Woiciechowski, A.L.; Karp, S.G.; Thomaz-Soccol, V.; Martínez-Burgos, W.J.; Penha, R.O.; Herrmann, L.W.; et al. Solid-State Fermentation Technology and Innovation for the Production of Agricultural and Animal Feed Bioproducts. Syst. Microbiol. Biomanuf. 2021, 1, 142–165. [Google Scholar] [CrossRef]
  8. Rothmann, C.; Rothmann, L.; Viljoen, B.; Cason, E.D. Application of Solid-State Fermentation Using Mushrooms for the Production of Animal Feed. J. Basic. Microbiol. 2023, 63, 1153–1164. [Google Scholar] [CrossRef] [PubMed]
  9. Farinas, C.S. Developments in Solid-State Fermentation for the Production of Biomass-Degrading Enzymes for the Bioenergy Sector. Renew. Sustain. Energy Rev. 2015, 52, 179–188. [Google Scholar] [CrossRef]
  10. Onu Olughu, O.; Tabil, L.G.; Dumonceaux, T.; Mupondwa, E.; Cree, D. Optimization of Solid-State Fermentation of Switchgrass Using White-Rot Fungi for Biofuel Production. Fuels 2022, 3, 730–752. [Google Scholar] [CrossRef]
  11. Khot, M.B. Solid-State Fermentation: An Alternative Approach to Produce Fungal Lipids as Biodiesel Feedstock BT. In Status and Future Challenges for Non-Conventional Energy Sources Volume 2; Joshi, S.J., Sen, R., Sharma, A., Salam, P.A., Eds.; Springer Nature: Singapore, 2022; pp. 123–137. ISBN 978-981-16-4509-9. [Google Scholar]
  12. Karimi, F.; Mazaheri, D.; Saei Moghaddam, M.; Mataei Moghaddam, A.; Sanati, A.L.; Orooji, Y. Solid-State Fermentation as an Alternative Technology for Cost-Effective Production of Bioethanol as Useful Renewable Energy: A Review. Biomass Convers. Biorefin 2021. [Google Scholar] [CrossRef]
  13. Banat, I.M.; Carboué, Q.; Saucedo-Castañeda, G.; De Jesús Cázares-Marinero, J. Biosurfactants: The Green Generation of Speciality Chemicals and Potential Production Using Solid-State Fermentation (SSF) Technology. Bioresour. Technol. 2021, 320, 124222. [Google Scholar] [CrossRef]
  14. Faria, D.J.; Carvalho, A.P.; Conte-Junior, C.A. Valorization of Fermented Food Wastes and Byproducts: Bioactive and Valuable Compounds, Bioproduct Synthesis, and Applications. Fermentation 2023, 9, 920. [Google Scholar] [CrossRef]
  15. Mattedi, A.; Sabbi, E.; Farda, B.; Djebaili, R.; Mitra, D.; Ercole, C.; Cacchio, P.; Del Gallo, M.; Pellegrini, M. Solid-State Fermentation: Applications and Future Perspectives for Biostimulant and Biopesticides Production. Microorganisms 2023, 11, 1408. [Google Scholar] [CrossRef]
  16. Dattatraya Saratale, G.; Bhosale, R.; Shobana, S.; Banu, J.R.; Pugazhendhi, A.; Mahmoud, E.; Sirohi, R.; Kant Bhatia, S.; Atabani, A.E.; Mulone, V.; et al. A Review on Valorization of Spent Coffee Grounds (SCG) towards Biopolymers and Biocatalysts Production. Bioresour. Technol. 2020, 314, 123800. [Google Scholar] [CrossRef] [PubMed]
  17. Lizardi-Jiménez, M.A.; Hernández-Martínez, R. Solid State Fermentation (SSF): Diversity of Applications to Valorize Waste and Biomass. 3 Biotech 2017, 7, 44. [Google Scholar] [CrossRef]
  18. Couto, S.R.; Gundín, M.; Lorenzo, M.; Sanromán, M.Á. Screening of Supports and Inducers for Laccase Production by Trametes Versicolor in Semi-Solid-State Conditions. Process Biochem. 2002, 38, 249–255. [Google Scholar] [CrossRef]
  19. Tsutsui, T.; Hayashi, N.; Maizumi, H.; Huff, J.; Barrett, J.C. Benzene-, Catechol-, Hydroquinone- and Phenol-Induced Cell Transformation, Gene Mutations, Chromosome Aberrations, Aneuploidy, Sister Chromatid Exchanges and Unscheduled DNA Synthesis in Syrian Hamster Embryo Cells. Mutat. Res. 1997, 373, 113–123. [Google Scholar] [CrossRef]
  20. Leonowicz, A.; Matuszewska, A.; Luterek, J.; Ziegenhagen, D.; Wojtaś-Wasilewska, M.; Cho, N.S.; Hofrichter, M.; Rogalski, J. Biodegradation of Lignin by White Rot Fungi. Fungal Genet. Biol. 1999, 27, 175–185. [Google Scholar] [CrossRef]
  21. Šelo, G.; Planinić, M.; Tišma, M.; Tomas, S.; Koceva Komlenić, D.; Bucić-Kojić, A. A Comprehensive Review on Valorization of Agro-Food Industrial Residues by Solid-State Fermentation. Foods 2021, 10, 927. [Google Scholar] [CrossRef]
  22. Son, N.H.; Lan, B.T.P.; Minh, N.D. The Current Status of Agricultural Wastes and Residuals Management and Recycling in Vietnam. In Practice and Benefits of Circular Agriculture in Waste Reducing and Recycling; Food and Fertilizer Technology Center: Taipei, Taiwan, 2021. [Google Scholar]
  23. Razavizadeh, S.; Alencikiene, G.; Salaseviciene, A.; Vaiciulyte-Funk, L.; Ertbjerg, P.; Zabulione, A. Impact of Fermentation of Okara on Physicochemical, Techno-Functional, and Sensory Properties of Meat Analogues. Eur. Food Res. Technol. 2021, 247, 2379–2389. [Google Scholar] [CrossRef]
  24. Sengupta, S.; Chakraborty, M.; Bhowal, J.; Bhattacharya, D. Study on the Effects of Drying Process on the Composition and Quality of Wet Okara. Int. J. Sci. Environ. Technol. 2012, 1, 319–330. [Google Scholar]
  25. Toda, K.; Chiba, K.; Ono, T. Effect of Components Extracted from Okara on the Physicochemical Properties of Soymilk and Tofu Texture. J. Food Sci. 2007, 72, C108–C113. [Google Scholar] [CrossRef] [PubMed]
  26. Li, B.; Qiao, M.; Lu, F. Composition, Nutrition, and Utilization of Okara (Soybean Residue). Food Rev. Int. 2012, 28, 231–252. [Google Scholar] [CrossRef]
  27. Kim, H.-S.; Yu, O.-K.; Byun, M.-S.; Cha, Y.-S. Okara, a Soybean by-Product, Prevents High Fat Diet-Induced Obesity and Improves Serum Lipid Profiles in C57BL/6J Mice. Food Sci. Biotechnol. 2016, 25, 607–613. [Google Scholar] [CrossRef]
  28. Asghar, A.; Afzaal, M.; Saeed, F.; Ahmed, A.; Ateeq, H.; Shah, Y.A.; Islam, F.; Hussain, M.; Akram, N.; Shah, M.A. Valorization and Food Applications of Okara (Soybean Residue): A Concurrent Review. Food Sci. Nutr. 2023, 11, 3631–3640. [Google Scholar] [CrossRef]
  29. Yimin, C.; Napasirth, V.; Napasirth, P.; Sulinthone, T.; Phommachanh, K. Microbial Population, Chemical Composition and Silage Fermentation of Cassava Residues. Anim. Sci. J. 2015, 86, 842–848. [Google Scholar] [CrossRef]
  30. Fanelli, N.S.; Torres-Mendoza, L.J.; Abelilla, J.J.; Stein, H.H. Chemical Composition of Cassava-Based Feed Ingredients from South-East Asia. Anim. Biosci. 2023, 36, 908–919. [Google Scholar] [CrossRef]
  31. Okrathok, S.; Thumanu, K.; Pukkung, C.; Molee, W.; Khempaka, S. Extraction of Dietary Fibers from Cassava Pulp and Cassava Distiller’s Dried Grains and Assessment of Their Components Using Fourier Transform Infrared Spectroscopy to Determine Their Further Use as a Functional Feed in Animal Diets. Anim. Biosci. 2022, 35, 1048–1058. [Google Scholar] [CrossRef]
  32. Dang, P.K.; Huong, D.T. Protein Enrichment of Cassava Residues by Simultaneous Saccharification and Fermentation. Vietnam. J. Agric. Sci. 2018, 16, 207–214. [Google Scholar]
  33. Zhu, J.; Tan, W.K.; Song, X.; Gao, Z.; Wen, Y.; Ong, C.N.; Loh, C.S.; Swarup, S.; Li, J. Converting Okara to Superabsorbent Hydrogels as Soil Supplements for Enhancing the Growth of Choy Sum (Brassica sp.) under Water-Limited Conditions. ACS Sustain. Chem. Eng. 2020, 8, 9425–9433. [Google Scholar] [CrossRef]
  34. Sabater, C.; Ruiz, L.; Delgado, S.; Ruas-Madiedo, P.; Margolles, A. Valorization of Vegetable Food Waste and By-Products through Fermentation Processes. Front. Microbiol. 2020, 11, 581997. [Google Scholar] [CrossRef]
  35. Oktaviani, N.; Sarwono, K.A.; Utama, G.I. Bioconversion Rice Bran and Cassava Peel into Yeasts Cell Walls Mannoprotein as Environmental Friendly Antioxidant. E3S Web Conf. 2021, 249, 3004. [Google Scholar] [CrossRef]
  36. Suriyapha, C.; Supapong, C.; So, S.; Wanapat, M.; Cherdthong, A. Bioconversion of Agro-Industrial Residues as a Protein Source Supplementation for Multiparous Holstein Thai Crossbreed Cows. PLoS ONE 2022, 17, e0273916. [Google Scholar] [CrossRef]
  37. Verardi, A.; Sangiorgio, P.; Blasi, A.; Lopresto, C.G.; Calabrò, V. Bioconversion of Crop Residues Using Alternative Fermentation-Based Approaches. Front. Biosci. 2023, 15, 17. [Google Scholar] [CrossRef]
  38. Bala, S.; Garg, D.; Sridhar, K.; Inbaraj, B.S.; Singh, R.; Kamma, S.; Tripathi, M.; Sharma, M. Transformation of Agro-Waste into Value-Added Bioproducts and Bioactive Compounds: Micro/Nano Formulations and Application in the Agri-Food-Pharma Sector. Bioengineering 2023, 10, 152. [Google Scholar] [CrossRef]
  39. Blasi, A.; Verardi, A.; Lopresto, C.G.; Siciliano, S.; Sangiorgio, P. Lignocellulosic Agricultural Waste Valorization to Obtain Valuable Products: An Overview. Recycling 2023, 8, 61. [Google Scholar] [CrossRef]
  40. Adnane, I.; Taoumi, H.; Elouahabi, K.; Lahrech, K.; Oulmekki, A. Valorization of Crop Residues and Animal Wastes: Anaerobic Co-Digestion Technology. Heliyon 2024, 10, e26440. [Google Scholar] [CrossRef] [PubMed]
  41. Cruz, I.A.; Santos Andrade, L.R.; Bharagava, R.N.; Nadda, A.K.; Bilal, M.; Figueiredo, R.T.; Romanholo Ferreira, L.F. Valorization of Cassava Residues for Biogas Production in Brazil Based on the Circular Economy: An Updated and Comprehensive Review. Clean. Eng. Technol. 2021, 4, 100196. [Google Scholar] [CrossRef]
  42. Deepalakshmi, K.; Sankaran, M. Pleurotus ostreatus: An Oyster Mushroom with Nutritional and Medicinal Properties. J. Biochem. Technol. 2014, 5, 718–726. [Google Scholar]
  43. Murphy, E.J.; Rezoagli, E.; Pogue, R.; Simonassi-Paiva, B.; Abidin, I.I.Z.; Fehrenbach, G.W.; O’neil, E.; Major, I.; Laffey, J.G.; Rowan, N. Immunomodulatory Activity of β-Glucan Polysaccharides Isolated from Different Species of Mushroom—A Potential Treatment for Inflammatory Lung Conditions. Sci. Total Environ. 2022, 809, 152177. [Google Scholar] [CrossRef]
  44. Yang, B.-K.; Gu, Y.-A.; Jeong, Y.-T.; Song, C.-H. Anti-Complementary Activities of Exo- and Endo-Biopolymer Produced by Submerged Mycelial Culture of Eight Different Mushrooms. Mycobiology 2007, 35, 145–149. [Google Scholar] [CrossRef]
  45. Dubois, M.; Gilles, K.A.; Hamilton, J.K.; Rebers, P.A.; Smith, F. Colorimetric Method for Determination of Sugars and Related Substances. Anal. Chem. 1956, 28, 350–356. [Google Scholar] [CrossRef]
  46. Phirom-On, K.; Apiraksakorn, J. Development of Cellulose-Based Prebiotic Fiber from Banana Peel by Enzymatic Hydrolysis. Food Biosci. 2021, 41, 101083. [Google Scholar] [CrossRef]
  47. Elbing, K.L.; Brent, R. Recipes and Tools for Culture of Escherichia coli. Curr. Protoc. Mol. Biol. 2019, 125, e83. [Google Scholar] [CrossRef]
  48. Huebner, J.; Wehling, R.L.; Parkhurst, A.; Hutkins, R.W. Effect of Processing Conditions on the Prebiotic Activity of Commercial Prebiotics. Int. Dairy J. 2008, 18, 287–293. [Google Scholar] [CrossRef]
  49. ISO 5983-2:2009; Animal Feeding Stuffs—Determination of Nitrogen Content and Calculation of Crude Protein Content. International Standard Organization: Geneva, Switzerland, 2009.
  50. ISO 6492:1999; Animal Feeding Stuffs—Determination of Fat Content. International Standard Organization: Geneva, Switzerland, 1999.
  51. ISO 5984:2022; Animal Feeding Stuffs—Determination of Crude Ash. International Standard Organization: Geneva, Switzerland, 2022.
  52. Nair, M.P.; Padmaja, G.; Sankarakutty, S.; Sheriff, T. Bioconversion of Cellulo-Starch Waste from Cassava Starch Industries for Ethanol Production: Pretreatment Techniques and Improved Enzyme Systems. Ind. Biotechnol. 2012, 8, 300–308. [Google Scholar] [CrossRef]
  53. O’Toole, D.K. Characteristics and Use of Okara, the Soybean Residue from Soy Milk Production—A Review. J. Agric. Food Chem. 1999, 47, 363–371. [Google Scholar] [CrossRef] [PubMed]
  54. Adenipekun, C.O.; Jonathan, G. Nutritional Requirements of Pleurotus florida (Mont.) Singer, A Nigerian Mushroom. Pak. J. Nutr. 2006, 5, 597–600. [Google Scholar] [CrossRef]
  55. Lu, X.; Zhao, Y.; Li, F.; Liu, P. Active Polysaccharides from Lentinula edodes and Pleurotus ostreatus by Addition of Corn Straw and Xylosma Sawdust through Solid-State Fermentation. Int. J. Biol. Macromol. 2023, 228, 647–658. [Google Scholar] [CrossRef]
  56. Heidari, F.; Øverland, M.; Hansen, J.Ø.; Mydland, L.T.; Urriola, P.E.; Chen, C.; Shurson, G.C.; Hu, B. Solid-State Fermentation of Pleurotus ostreatus to Improve the Nutritional Profile of Mechanically-Fractionated Canola Meal. Biochem. Eng. J. 2022, 187, 108591. [Google Scholar] [CrossRef]
  57. Tolera, K.D.; Abera, S. Nutritional Quality of Oyster Mushroom (Pleurotus ostreatus) as Affected by Osmotic Pretreatments and Drying Methods. Food Sci. Nutr. 2017, 5, 989–996. [Google Scholar] [CrossRef]
  58. Ayimbila, F.; Keawsompong, S. Nutritional Quality and Biological Application of Mushroom Protein as a Novel Protein Alternative. Curr. Nutr. Rep. 2023, 12, 290–307. [Google Scholar] [CrossRef] [PubMed]
  59. Tu, J.; Brennan, M.; Brennan, C. An Insight into the Mechanism of Interactions between Mushroom Polysaccharides and Starch. Curr. Opin. Food Sci. 2021, 37, 17–25. [Google Scholar] [CrossRef]
  60. Gibson, G.R.; Hutkins, R.; Sanders, M.E.; Prescott, S.L.; Reimer, R.A.; Salminen, S.J.; Scott, K.; Stanton, C.; Swanson, K.S.; Cani, P.D.; et al. Expert Consensus Document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) Consensus Statement on the Definition and Scope of Prebiotics. Nat. Rev. Gastroenterol. Hepatol. 2017, 14, 491–502. [Google Scholar] [CrossRef]
  61. Peng, M.; Tabashsum, Z.; Anderson, M.; Truong, A.; Houser, A.K.; Padilla, J.; Akmel, A.; Bhatti, J.; Rahaman, S.O.; Biswas, D. Effectiveness of Probiotics, Prebiotics, and Prebiotic-like Components in Common Functional Foods. Compr. Rev. Food Sci. Food safety 2020, 19, 1908–1933. [Google Scholar] [CrossRef] [PubMed]
  62. De Figueiredo, F.C.; De Barros Ranke, F.F.; De Oliva-Neto, P. Evaluation of Xylooligosaccharides and Fructooligosaccharides on Digestive Enzymes Hydrolysis and as a Nutrient for Different Probiotics and Salmonella typhimurium. LWT 2020, 118, 108761. [Google Scholar] [CrossRef]
  63. Hang, N.T.B.; Cuong, D.C.; Nhat, D.M.; Thang, D.B. Prebiotic Properties of Polysaccharides Isolated from Cordyceps Militaris Mycelia. Vietnam. Trade Ind. Rev. 2023, 4, 413–420. [Google Scholar]
  64. Aida, F.M.N.A.; Shuhaimi, M.; Yazid, M.; Maaruf, A.G. Mushroom as a Potential Source of Prebiotics: A Review. Trends Food Sci. Technol. 2009, 20, 567–575. [Google Scholar] [CrossRef]
  65. Synytsya, A.; Míčková, K.; Synytsya, A.; Jablonský, I.; Spěváček, J.; Erban, V.; Kováříková, E.; Čopíková, J. Glucans from Fruit Bodies of Cultivated Mushrooms Pleurotus ostreatus and Pleurotus eryngii: Structure and Potential Prebiotic Activity. Carbohydr. Polym. 2009, 76, 548–556. [Google Scholar] [CrossRef]
  66. Huebner, J.; Wehling, R.L.; Hutkins, R.W. Functional Activity of Commercial Prebiotics. Int. Dairy. J. 2007, 17, 770–775. [Google Scholar] [CrossRef]
  67. Barrangou, R.; Altermann, E.; Hutkins, R.; Cano, R.; Klaenhammer, T. Functional and Comparative Genomic Analyses of an Operon Involved in Fructooligosaccharide Utilization by Lactobacillus acidophilus. Proc. Natl. Acad. Sci. USA 2003, 100, 8957–8962. [Google Scholar] [CrossRef]
Fermentation 11 00271 g001
Figure 1. The development of the P. ostreatus mycelium during SSF. CT1: 100% cassava residue; CT2: 90% cassava + 10% soybean residue; CT3: 80% cassava + 20% soybean residue; CT4: 70% cassava + 30% soybean residue; and CT5: 60% cassava + 40% soybean residue.
Figure 1. The development of the P. ostreatus mycelium during SSF. CT1: 100% cassava residue; CT2: 90% cassava + 10% soybean residue; CT3: 80% cassava + 20% soybean residue; CT4: 70% cassava + 30% soybean residue; and CT5: 60% cassava + 40% soybean residue.
Fermentation 11 00271 g001
Fermentation 11 00271 g002
Figure 2. Content of PS, protein, starch, total lipid, and total ash (mg/100 g) in the substrate before and after SSF.
Figure 2. Content of PS, protein, starch, total lipid, and total ash (mg/100 g) in the substrate before and after SSF.
Fermentation 11 00271 g002
Fermentation 11 00271 g003
Figure 3. Impact of polysaccharides extracted from fermented substrate on probiotic growth. (a): P. acidilactici NBD8, (b): L. pentosus NH1, (c): L. argentoraten NH15, and (d): L. plantarum WCFS1. Where GF is MRS medium without glucose, Glc is GF medium supplemented with 1 g/L glucose, PS is GF medium supplemented with 1 g/L PS, Pre is GF medium supplemented with 1 g/L commercial prebiotic, GlPs is Glc medium supplemented with 1 g/L PS, and GlPre is Glc medium supplemented with 1 g/L commercial prebiotic.
Figure 3. Impact of polysaccharides extracted from fermented substrate on probiotic growth. (a): P. acidilactici NBD8, (b): L. pentosus NH1, (c): L. argentoraten NH15, and (d): L. plantarum WCFS1. Where GF is MRS medium without glucose, Glc is GF medium supplemented with 1 g/L glucose, PS is GF medium supplemented with 1 g/L PS, Pre is GF medium supplemented with 1 g/L commercial prebiotic, GlPs is Glc medium supplemented with 1 g/L PS, and GlPre is Glc medium supplemented with 1 g/L commercial prebiotic.
Fermentation 11 00271 g003
Fermentation 11 00271 g004
Figure 4. The optical density values of bacteria when cultivated in medium with different carbon sources at 37 °C over 24 h. Where GF: MRS medium without glucose, Glc: GF medium supplemented with 1 g/L glucose, Pre: GF medium supplemented with 1 g/L commercial prebiotic; and PS: GF medium supplemented with 1 g/L PS.
Figure 4. The optical density values of bacteria when cultivated in medium with different carbon sources at 37 °C over 24 h. Where GF: MRS medium without glucose, Glc: GF medium supplemented with 1 g/L glucose, Pre: GF medium supplemented with 1 g/L commercial prebiotic; and PS: GF medium supplemented with 1 g/L PS.
Fermentation 11 00271 g004
Fermentation 11 00271 g005
Figure 5. Selective prebiotic stimulation characteristics of bacterial strains through the prebiotic index.
Figure 5. Selective prebiotic stimulation characteristics of bacterial strains through the prebiotic index.
Fermentation 11 00271 g005
Table 1. Blending treatments for cassava and soybean residues.
Table 1. Blending treatments for cassava and soybean residues.
Treatments 1Cassava Residue (%)Soybean Residue (%)
CT1 (n = 15)1000
CT2 (n = 15)9010
CT3 (n = 15)8020
CT4 (n = 15)7030
CT5 (n = 15)6040
1 Each treatment was prepared in 5 samples and repeated three times. Both cassava and soybean residues were in dry substrate.
Table 2. Changes in the diameter (mm) of P. ostreatus mycelium on treatments during cultivation.
Table 2. Changes in the diameter (mm) of P. ostreatus mycelium on treatments during cultivation.
TreatmentsCulture Time (Days)Characteristics of Mycelium
1st3rd5th7th9th
CT1 (n = 15)1.77 ± 0.15 a19.37 ± 1.32 a51.8 ± 3.93 a110.62 ± 3.45 a120 ± 0 aFine, low density
CT2 (n = 15)0.91 ± 0.05 b10.26 ± 1.42 c33.99 ± 2.04 b83.18 ± 3.59 b120 ± 0 aFine, evenly white, low density
CT3 (n = 15)1.73 ± 0.17 a13.32 ± 1.04 b34.56 ± 2.41 b82.51 ± 3.66 b120 ± 0 aThick, evenly white, high density
CT4 (n = 15)0.97 ± 0.03 b6.47 ± 0.81 d24.01 ± 1.68 c60.06 ± 2.99 c108.07 ± 3.85 bThick, fluffy, evenly white, high density
CT5 (n = 15)0.91 ± 0.03 b2.69 ± 0.53 e11.56 ± 1.29 d41.61 ± 2.35 d84.29 ± 3.52 cThick, fluffy, high density
Note: Values are mean ± standard error of the mean (n = 15). Means followed by the same letter within a column are not significantly different according to the Tukey HSD test for a significance level of 95%.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Hang, N.T.B.; Doan, C.C. Improving Nutrition Facts of Cassava and Soybean Residue Through Solid-State Fermentation by Pleurotus ostreatus Mycelium: A Pathway to Safety Animal Feed Production. Fermentation 2025, 11, 271. https://doi.org/10.3390/fermentation11050271

AMA Style

Hang NTB, Doan CC. Improving Nutrition Facts of Cassava and Soybean Residue Through Solid-State Fermentation by Pleurotus ostreatus Mycelium: A Pathway to Safety Animal Feed Production. Fermentation. 2025; 11(5):271. https://doi.org/10.3390/fermentation11050271

Chicago/Turabian Style

Hang, Nguyen Thi Bich, and Chi Cuong Doan. 2025. "Improving Nutrition Facts of Cassava and Soybean Residue Through Solid-State Fermentation by Pleurotus ostreatus Mycelium: A Pathway to Safety Animal Feed Production" Fermentation 11, no. 5: 271. https://doi.org/10.3390/fermentation11050271

APA Style

Hang, N. T. B., & Doan, C. C. (2025). Improving Nutrition Facts of Cassava and Soybean Residue Through Solid-State Fermentation by Pleurotus ostreatus Mycelium: A Pathway to Safety Animal Feed Production. Fermentation, 11(5), 271. https://doi.org/10.3390/fermentation11050271

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop