Sustainable Valorization of Plant Residues Through Enzymatic Hydrolysis for the Extraction of Bioactive Compounds: Applications as Functional Ingredients in Cosmetics

Abstract

The growing demand for sustainable and environmentally friendly cosmetic products has driven innovations using plant residues as raw materials for high-value-added applications. This study focuses on the enzymatic hydrolysis of plant residues to extract bioactive compounds, with the potential for application as functional ingredients in cosmetics. Enzymatic processes are highlighted for their ability to optimize extraction, preserving the bioactivity of the compounds while significantly reducing the environmental footprint compared to conventional resource-intensive methods. This work emphasizes scientific articles that incorporate the principles of the circular economy, promoting the reuse of solid waste and mitigating the need to extract new natural resources. The valorization of waste through advanced biotechnological technologies addresses critical environmental challenges and offers innovative solutions that transform agro-industrial by-products into high-value inputs for the cosmetic industry. The results presented reinforce this approach’s feasibility and positive impact, promoting economic and environmental benefits. This study highlights the transformative role of enzymatic hydrolysis in the transition toward a more sustainable, efficient cosmetics industry integrated with global decarbonization goals.

1. Introduction

The escalating demand for food, driven by population growth, has intensified waste generation at all stages of the agri-food chain, from production to end-user consumption [1]. Approximately one-third of all food produced globally is lost or wasted annually, corresponding to 2.5 billion tons [2]. This scenario raises social and economic concerns and environmental issues due to inadequate disposal methods (landfills and incineration), which are characterized by high energy consumption and substantial greenhouse gas emissions [3].

To address the pressing issues of waste generation and environmental impact, implementing sustainable valorization strategies for agro-industrial and food waste has become imperative. These approaches aim to recover high-value compounds while reducing ecological harm from landfill-dependent disposal systems. Figure 1 illustrates the trend in the number of scientific publications indexed in the ScienceDirect database between 2014 and 2024 based on the keywords “Plant residues waste”, “Plant waste”, and “Plant residue”. This growth reflects heightened scientific and industrial interest in circular-economy solutions, which is driven by regulatory incentives and consumer demand for greener practices.

Various agro-industrial residues, such as peels, seeds, bagasse, and wastewater from extraction and purification processes, exhibit high potential for the production of bioproducts, including biofertilizers, bioethanol, biolipids, and biodegradable polymers [4,5,6,7]. The soybean industry, for example, seeks to implement integrated systems to fully utilize by-products such as okara, soy whey, and hulls, applying biorefinery technologies and circular-economy principles to achieve zero-waste processing models [8]. Similarly, lignocellulosic residues derived from Camellia oleifera oil extraction have been converted into fermentable sugars through optimized acid pretreatments and enzymatic hydrolysis, balancing process efficiency with resource conservation [9].

Advanced technologies have played a fundamental role in enabling these alternatives, with particular attention to processes such as subcritical hydrolysis, which transforms biomass into sugars without harsh chemical reagents. However, challenges related to solid-to-liquid ratios continue to limit its application on an industrial scale [10]. Furthermore, green solvents, such as deep eutectic solvents (DESs) and natural deep eutectic solvents (NADESs), have emerged as promising alternatives for the sustainable extraction of bioactive compounds from agro-industrial residues, offering lower toxicity and environmental impact compared to conventional organic solvents [11].

Nevertheless, despite technological advances and identified opportunities, the implementation of waste valorization strategies still faces challenges related to the variability of waste composition, the presence of antinutritional factors, and technical and economic limitations in integrating these processes into established production chains [12]. In this regard, studies exploring integrated and innovative approaches to the recovery of food and agro-industrial waste are important to support the transition toward more sustainable, resilient, and circular food systems.

The valorization of agro-industrial waste through sustainable and innovative processes becomes an opportunity for bioenergy and biomaterials production and for generating high-value compounds applicable in other industries, such as cosmetics. The cosmetic industry has prioritized safety and sustainability, developing cosmetics and cosmeceuticals formulated with safe, environmentally friendly, and cruelty-free ingredients. This trend responds to the growing demand for products that replace or reduce the use of active ingredients and components that do not meet these criteria [13,14,15].

The application of native proteins in cosmetic formulations is mainly limited by their low water solubility. However, this limitation can be overcome through enzymatic hydrolysis, which enhances the solubility and improves the functional properties of hydrolysates, such as surface hydrophobicity, emulsifying and foaming capacity, substantivity, film-forming ability, improved skin penetration, and increased moisture retention and shine [16,17,18,19,20]. These characteristics make hydrolysates promising ingredients for high-performance cosmetic products.

Protein hydrolysates and their derivatives—polypeptides, oligopeptides, and peptides in particular—are widely used in the cosmetic industry as conditioning agents for hair and skin, owing to their ability to perform various biological functions in skin cells. These compounds can activate signaling pathways and regulate key genetic mechanisms, resulting in beneficial effects on the skin. Furthermore, unlike larger proteins, peptides exhibit superior penetration into the deeper layers of the skin, offering a more efficient and effective delivery system [21,22].

Bioactive peptides are compounds with specific biological functions, including enzyme inhibition, as well as antimicrobial, antioxidant, and anti-inflammatory activities [23,24,25,26]. Enzymatic hydrolysis can also serve as an effective pretreatment to facilitate the recovery of phenolic compounds from agro-industrial residues such as brewer’s spent grain, fruit peels, bran, and other plant by-products [27,28,29,30,31,32]. This pretreatment disrupts the lignocellulosic matrix, releasing phenolic compounds that are often bound to polysaccharides and proteins, thereby increasing their bioavailability and extraction efficiency. Consequently, enzymatic hydrolysis optimizes the recovery of bioactive compounds and contributes to waste valorization by promoting the development of high-value functional ingredients for the cosmetic industry and other applications.

Agro-industrial by-products are emerging as valuable sources of peptides and phenolic compounds, particularly through hydrolysis [33,34]. Protein concentrations in food-industry residues typically range from 5.5% to 42.2% (mean ≈ 20.5%), underscoring their suitability for bioconversion into biopeptides and amino acids [35].

Among these residues, brewer’s spent grain (BSG) and brewer’s spent hops (BSHs) stand out as rich sources of natural antioxidants. BSG contains 12–25% cellulose, 20–25% hemicellulose, and 12–28% lignin, along with 7.5–13.3% sugars, 15.9–35% proteins, and 6.4–13% lipids. In contrast, BSHs are low in lipids (~1%) but particularly high in proteins and amino acids (40–52%). The total phenolic content in BSG has been reported at 7–10 mg gallic-acid equivalents (GAEs)/g, whereas BSHs range from 10 to 18 mg GAEs/g [36]. Through optimized extraction, BSG can yield 24.84–38.83 µmol of GAEs/g of polyphenols, with ferulic acid as the predominant compound, a molecule not detected in BSHs extracts [37].

Citrus peels (sweet oranges, grapefruits, Ellendale mandarins, and Yen Ben lemons) are also prolific sources of high-value phenolic acids—ferulic, p-coumaric, sinapic, caffeic, vanillic, gallic, and chlorogenic. Sweet orange residues exhibit the highest total phenolic content (1790 mg GAEs/g), followed by grapefruit (1550 mg GAEs/g), mandarin (1211 mg GAEs/g), and lemon (1190 mg GAEs/g) [38]. Upcycling these residues provides a cost-effective source of natural antioxidants and advances circular economy practices by transforming materials that would otherwise be discarded or underutilized into high-value bioactive ingredients (Figure 2).

Therefore, this article explores the potential for sustainable valorization of plant-based residues through enzymatic hydrolysis, focusing on the extraction of bioactive compounds for application as functional ingredients in cosmetic formulations. The growing demand for sustainable and environmentally friendly cosmetics, combined with the need for industrial practices that promote circularity and waste reduction, underscores the importance of developing innovative processes with minimal environmental impact.

2. Fundamental Principles of Enzymatic Hydrolysis

Enzymatic hydrolysis cleaves large biomolecules into smaller fragments by incorporating water across specific chemical bonds. Unlike chemical hydrolysis, which relies on strong acids or bases, enzymatic processes employ enzymes that operate under mild temperature and pH conditions [39,40]. This selectivity lowers energy requirements and minimizes hazardous by-products, but it also preserves the structural integrity and bioactivity of the released compounds [41,42].

Beyond its environmental advantages, enzymatic hydrolysis aligns with broader sustainability goals due to the renewable and biodegradable nature of enzymes. These biological catalysts naturally integrate into ecological cycles, supporting principles of the circular economy [43]. The valorization of agro-industrial by-products has gained momentum in response to increasing sustainability demands and the scarcity of natural resources.

The application of enzymatic hydrolysis enables the efficient conversion of plant residues into high-value raw materials, thereby facilitating the recycling and reuse of these by-products [44]. This strategy not only mitigates greenhouse gas emissions and reduces the volume of waste destined for landfills but also ensures that the process aligns with global sustainable development objectives [45,46].

Different enzymes, including cellulases, hemicellulases, pectinases, and proteases, target distinct components of plant cell walls and intracellular matrices. These enzymes facilitate the degradation of complex carbohydrates, proteins, and other macromolecules [42,47]. The proteases can be applied individually or in combinations to optimize reaction efficiency and the peptide profile.

Among the most commonly used proteases is Alcalase^®, which is a serine endoprotease derived from Bacillus licheniformis and commercially formulated as a liquid preparation containing glycerol, water, and protease extract [48,49]. Bromelain, a cysteine endoprotease extracted from the stem of Ananas comosus, is another widely utilized enzyme known for its broad substrate specificity [50]. Neutrase^®, a zinc-dependent metalloprotease from Bacillus amyloliquefaciens, is valued for its neutral activity and broad cleavage profile [51]. Flavourzyme^®, produced by Aspergillus oryzae, combines exo- and endoproteolytic activity, including aminopeptidases and carboxypeptidases, resulting in hydrolysates with low bitterness and improved sensory properties [51]. Protamex^®, another protease complex derived from Bacillus spp., is known for its versatility in producing hydrolysates with various degrees of hydrolysis and functional profiles [52].

For carbohydrate breakdown, Viscozyme^® L (Aspergillus aculeatus) combines arabinase, cellulase, β-glucanase, hemicellulase, and xylanase activities to dismantle lignocellulosic scaffolds, thereby enhancing protein and phenolic release [53,54].

Enzymatic hydrolysis valorizes plant by-products through a multistep mechanism, starting with an initial pretreatment to disrupt lignocellulosic structures and expose cell wall polymers followed by adsorption of hydrolytic enzymes onto substrate surfaces through specific interactions between active sites [55,56]. Cellulases, hemicellulases, and pectinases synergistically cleave β-1,4-glycosidic bonds, ester bonds, and pectic galacturonan, releasing soluble oligosaccharides, monosaccharides, and phenolic glycosides [57]. This hydrolytic release generates phenolic aglycones and bioactive peptides through the rupture of glycosidic and peptide bonds, which significantly increases molecular solubility and bioavailability.

Despite its potential, the integration of enzymatic hydrolysis into large-scale industrial processes presents challenges. These include high operational costs, difficulties in scaling up, and limitations of enzymes in breaking down complex plant cell wall structures [58]. Enzymes require controlled conditions to maintain their activity and stability, which may not be easily replicated in industrial settings, limiting their efficiency and increasing production costs.

To overcome these challenges, process design and technology are needed to establish databases of hydrolysate properties, coupled with comprehensive techno-economic assessments that can inform enzyme selection and operational planning [59]. Additionally, leveraging modern computational tools, such as in silico simulations and bioinformatics, can significantly enhance enzyme and substrate selection, while the incorporation of green technologies like ultrasound, microwave-assisted extraction, and pulsed electric fields offers promising avenues to improve yield and reduce environmental impact [60].

The development of continuous bioreactors, including membrane-based and immobilized enzyme systems, further supports prolonged, stable operations and lower production costs. Equally important is the need to navigate the regulatory landscape to secure market acceptance, a challenge best met through strengthened collaboration between academic researchers and industry stakeholders, ensuring that scientific innovations translate effectively into commercially viable products [59].

3. Valorization of Plant By-Products Through Enzymatic Hydrolysis

The valorization of plant by-products through enzymatic hydrolysis has gained increasing prominence as a sustainable strategy to recover high-value compounds from agro-industrial residues, which are often rich in fibers, proteins, lipids, and bioactive molecules [61]. By-products, including husks and seeds, have demonstrated significant potential for applications in the pharmaceutical, cosmetic, and nutraceutical sectors due to their high content of phenolic compounds, such as polyphenols, oligophenols, and monophenols [62,63,64,65].

After enzymatic hydrolysis of plant by-products, the resulting bioactive compounds are typically characterized by a combination of physicochemical (protein content, aminogram, degree of hydrolysis, yield, content of phenolic compounds, high-performance liquid chromatography, gas chromatography, solubility, and stability) and biological (antioxidant, antimicrobial, anti-inflammatory activity, and enzyme inhibition) analyses to assess their potential for industrial applications, particularly in cosmetics and pharmaceuticals.

Numerous studies attest to the versatility of enzyme-assisted extractions (EAEs). For instance, [66] reported the effective valorization of chokeberry pomace through EAEs using cellulolytic and xylanolytic enzymes, which significantly enhanced the recovery of water-soluble fractions, monosaccharides, and phenolic compounds while also improving antioxidant properties.

Similarly, El Kantar et al. [67] optimized the release of fermentable sugars and polyphenols from orange peels through enzymatic hydrolysis with Viscozyme^® L, both independently and in combination with high-voltage electrical discharges, demonstrating the synergistic effect of physical and enzymatic treatments. In the context of fruit seed valorization, the enzymatic hydrolysis of plum seeds generated bioactive peptides with antioxidant and antihypertensive activities, particularly through the use of Alcalase^® [68], while a one-pot protease-based extraction enabled the sustainable recovery of oils and proteins from various fruit seeds and kernels, with oils rich in unsaturated fatty acids and protein hydrolysates showing moderate degrees of hydrolysis [69].

Furthermore, Meini et al. [70] optimized the aqueous enzymatic extraction of phenolic compounds from grape pomace using a combination of pectinase, cellulase, and tannase, achieving a 66% increase in phenolic yield and an 80% enhancement in antioxidant capacity. These studies collectively demonstrate the versatility of enzymatic hydrolysis as a sustainable and efficient approach for the valorization of diverse plant by-products, enabling the recovery of high-value bioactive compounds with potential applications across various industrial sectors.

Additionally, innovative applications include the extraction of natural pigments, such as the brown pigments from Camellia oleifera shells, which exhibited promising stability and bioactivity, including antioxidant and antimicrobial properties, following ultrasound-assisted enzymatic extraction [71]. Polysaccharides with anticancer potential have been obtained from Rosa roxburghii fruit through ultrasound-assisted enzymatic methods, with purified fractions inducing apoptosis in cancer cells via ROS-dependent pathways [72]. Furthermore, aqueous enzymatic extraction (AEE) has proven highly effective for oil recovery from various plant residues, including gardenia fruit [73], passion fruit peels [74], and Idesia polycarpa fruit [75].

These approaches, often optimized through statistical methodologies such as response surface designs, have resulted in higher extraction yields, improved nutritional profiles, and enhanced functional properties of oils, pectins, and other biomolecules when compared to conventional chemical or solvent-based methods.

Table 1. Studies on obtaining bioactive compounds through enzymatic hydrolysis.

By-Product	Enzymatic Treatment	Bioactive Compounds Obtained	Result	Reference
Various agro-industrial waste	Commercial enzymes (Cellulase, β-glucosidase, xylanase)	Phenolic compounds	Increase of up to 38.5% in the extraction of phenolic compounds and an increase in antioxidant activity by up to 3.5 times	[76]
Soybean hulls, straw, and corn cobs	Cellulase and Pectinase	Cellulose, hemicellulose	Increased digestibility and release of nutrients	[77]
Jatropha curcas cake (non-toxic)	Protease Alcalase	Bioactive peptides with antioxidant activity, antihypertensive, and antidiabetic capacity	Increased free radical reduction capacity and potential for treatment of chronic degenerative diseases	[78]
Jiuzao by-product of the Baijiu distillation process	Protease	Polyphenols, polypeptides, and alkaloids	Increased antioxidant capacity	[79]
Camellia (Camellia japonica) and rose (Rosa hybrida), and rosella (Hibiscus sabdariffa) flowers	Cellulase and Pectinase	Phenolic compounds and biosugars	Increased antioxidant capacity	[80]

summarizes key studies, highlighting improvements in extract quality and extraction efficiency achieved via enzymatic treatments.

The hemicellulase-assisted extract exhibited the highest antioxidant capacity in the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assay (5075 ± 43 mg Trolox equivalent (TE)/100 g), while the cellulase-assisted extract performed best in the 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay (8138 ± 31 mg TE/100 g dw). Enzyme-assisted extraction facilitated the release of phenolic compounds from the plant matrix, increasing their bioavailability and antioxidant properties [47]. Enzyme-treated chicory extract was able to inhibit the growth of S. aureus and P. aeruginosa after only 7 days of incubation [81]. Cold-pressed oil cake from pumpkin seed (Cucurbita pepo L.) inhibited 50% of the free radicals DPPH and ABTS at a concentration of 13.07 μg/mL and 64.70 μg/mL, respectively [82]. The protein extract derived from rice husks showed antioxidant capacity similar to the standards (25,327 ± 0.44%), such as those used in the cosmetic and food industry: butylated hydroxyanisole (BHA) with DPPH of 22.16%, butylhydroxytoluene (BHT) with DPPH of 31.31 ± 2.4, vitamin C with DPPH of 28.8 ± 1.47, and vitamin E with DPPH of 25.1 ± 3.04. This activity was possibly due to the presence of highly reactive amino acids [22].

4. Cosmetic Applications and Benefits of Bioactive Compounds Derived from Plant By-Products

Hydrolysates derived from soy, rice, and corn proteins have been evaluated by the Cosmetic Ingredient Review Expert Panel and are deemed safe for use in cosmetic products. These compounds play a critical role as skin and hair conditioning agents and are widely utilized due to their hydrating and protective properties. Similarly, hydrolyzed wheat gluten and hydrolyzed wheat protein have been classified as safe for cosmetic use, provided they are formulated with peptides of a molecular weight (MW) not exceeding 3500 Da. This specification ensures safety, efficacy, and a reduced risk of skin sensitization [83,84].

Bioactive peptides obtained through the hydrolysis of protein matrices demonstrate a broad spectrum of biological activities, making them up-and-coming candidates for innovative cosmeceutical product development. Notably, these peptides exhibit antioxidant, antimicrobial, and anti-inflammatory properties and can inhibit enzymes associated with skin aging, such as elastase, collagenase, tyrosinase, and hyaluronidase. By acting on these targets, they contribute directly to maintaining skin integrity and delaying the visible signs of aging [85].

Among bioactive peptides, those derived from the enzymatic hydrolysis of soy protein (Glycine max L.) and its by-products have been extensively studied for their antioxidant, anti-inflammatory, antiatherosclerotic, and anticarcinogenic effects [86,87]. Incorporating these peptides into cosmetic formulations enhances oxidative stress protection and promotes cellular renewal, yielding significant skin health benefits and multifunctional product opportunities.

Table 2. Studies on the enzymatic hydrolysis of by-products to extract peptides and bioactive compounds for application in the cosmetics industry.

By-Product	Enzymatic Hydrolysis Conditions	Results and Potential Applications	Reference
Grape marc seeds	Lallzyme EX-V enzyme, temperature of 48 °C, extraction time of 2 h and 43 min, pH 3.5, and enzyme dosage of 20.00 mg/g	Optimization of the extraction method for the recovery of phenols. The obtained extracts can be used in the cosmetic industry.	[88]
Rice starch processing by-product	Enzyme/substrate ratios of 0.5, 0.2, and 0.05 U enzyme/g protein; temperatures of 60 and 55 °C; volumes of 1 and 2 L; pH (Alcalase pH 7 and Protamex pH 8); and stirring at 300 rpm.	Putative application of these peptides as natural tyrosinase inhibitors in the cosmetics industry. Tyrosinase inhibition blocks melanin production in the skin, lightening and evening out skin tone.	[89]
Cichorium intybus bagasse	The samples were suspended in 0.05 M acetate buffer (pH 5.0) to a dry matter content of 5% (w/v) and mixed at 50 °C for 24 h. The enzymes were used alone or in combinations: inulinase, pectinase, cellulase, β-glucosidase, xylanase, and ferulic acid esterase. The enzyme dose was based on the protein content.	The hydrolysate showed antimicrobial activity against human skin pathogens but not beneficial skin microbes such as lactobacilli.	[81]
Hemp Seed Oil Cake	Protein concentration of 6.25 g/100 mL with 0.1 M phosphate buffer (pH 6.5). Bromelain was added at concentrations of 1%, 2%, or 3% relative to the protein content. Temperature reactions of 20 °C, 30 °C, or 40 °C for 60, 120, or 180 min.	Optimal conditions for obtaining protein hydrolysates with the highest antioxidant activity were achieved using a bromelain concentration of 3.0% at 40 °C for 60 min. The resulting product has potential applications in developing antiaging cosmetics and skin protection creams.	[82]
Rice husk	Protein concentration of 20 mg/mL, enzyme/substrate ratio of 1:10 (v/v), pH 10, and 50 °C. The reaction was performed in a water bath (80–90 °C), with constant stirring and pH controlled using 1 N NaOH. Reaction times ranged from 2.5 to 75 min.	Residue with low levels of gums, mucilage, and pectin and a high concentration of insoluble polysaccharides. Iβ cellulose presented potential for cosmetic applications. Degree of hydrolysis of 30.41% and a DPPH radical absorption rate of more than 70%.	[22]

presents studies highlighting the application of enzymatic hydrolysis as a method for extracting bioactive compounds from plant by-products, with a focus on their use as cosmetic ingredients.

From a circular economy perspective, agro-industrial residues, such as brewers’ spent grain (BSG), have garnered increasing attention as sustainable sources of bioactive compounds for the cosmetic industry. The enzymatic hydrolysis of BSG enhances the bioavailability of phenolic compounds and peptides, broadening their potential for industrial applications [90].

Peptides derived from BSG exhibit antioxidant, anti-inflammatory, and wound-healing properties, making them valuable ingredients for skin care and protective products [91]. Additionally, hydroxycinnamic acids in BSG, such as ferulic acid and p-coumaric acid, can be recovered and incorporated into cosmetic formulations to protect against premature aging and UV-induced damage [92].

Phenolic acids are particularly effective in preventing photoaging due to their high antioxidant capacity [93]. Furthermore, they exhibit depigmenting effects by inhibiting tyrosinase activity, thereby aiding in the reduction of hyperpigmentation [94]. These compounds also demonstrate antibacterial and anti-inflammatory properties, making them effective in wound healing and treating dermatological conditions such as acne, seborrheic dermatitis, and atopic dermatitis [95].

The extraction of polyphenols for the development of sustainable and high-performance cosmetics, exploiting their antioxidant, anti-inflammatory, and UV protection properties, requires enzymes specialized in degrading the cell wall, breaking down structural barriers, and releasing intracellular bioactives. The success of these extractions depends both on the appropriate choice of enzyme (alone or in customized enzyme cocktails) and on the fine-tuning of reaction conditions—pH, temperature, and ionic strength—to maximize catalytic activity and release efficiency of target compounds [96].

Enzymatic hydrolysis is a highly effective strategy for extracting bioactive compounds from grape pomace, including resveratrol, a potent antioxidant and anti-inflammatory agent widely used in cosmetic and pharmaceutical industries for its proven efficacy in preventing premature aging and reducing inflammation [64,65,67]. This process also facilitates the extraction of additional bioactive compounds from wine by-products, such as those with antiaging, anti-inflammatory, and wound-healing properties, thereby expanding the potential application of these agro-industrial residues in high-value cosmetic formulations [97,98].

Upcycling can be a promising business alternative for valorizing plant residues by transforming waste into profit. Innovative companies and startups are investing in the potential of ingredients derived from plant residues. TransferTech from Brazil, for instance, uses enzymatic technology to produce protein hydrolysates. Similarly, Upgrain employs the concept of upcycling to convert plant residues into sustainable raw materials. This process demonstrates how the strategic utilization of by-products can yield highly functional ingredients for biocosmetic applications, thereby bridging environmental sustainability with technological innovation. In parallel, the Brazilian startup Nun Tecnologia Sustentável has developed an exclusive extract from the secondary processing of olives.

Furthermore, waste valorization is also a central strategy for the Brazilian startup Cacaus Biocosméticos. By utilizing cocoa residues to formulate products, the company harnesses potent antioxidant properties and imparts anti-inflammatory and antimicrobial activities to its formulations. This approach significantly enhances the value of food-industry by-products and broadens the opportunities for developing effective and sustainable biocosmetic products.

5. Economic and Environmental Benefits of By-Products Recovery

Globalization, population growth, and the need for large-scale food production have led to the adoption of a linear agricultural model focused on immediate economic outcomes, often at the expense of environmental health. In contrast to traditional agriculture, which adhered to circular sustainability models by reintegrating waste into the production cycle, modern agriculture accumulates tons of waste in landfills. This practice squanders resources and hinders the recovery of bioactive compounds, such as polyphenols, flavonoids, tannins, and essential oils that possess significant antioxidant and anti-inflammatory properties and could be transformed into high-value-added products [97,98].

Despite their richness in bioactive compounds, plant by-products are commonly utilized in animal feed production. While this approach is considered a sustainable alternative, adding value to generated waste and reducing environmental impacts, it fails to exploit its potential fully. Valuable components that could be allocated to higher-value applications, such as human nutrition, nutraceutical products, and cosmetics, are lost. Consequently, recovering these ingredients through the valorization of agro-industrial by-products emerges as an innovative and promising strategy [99,100,101].

Utilizing agro-industrial waste for the extraction of bioactive compounds in cosmetics offers a new approach that transforms low-value by-products into high-value ingredients, reducing raw material costs and adding revenue streams for both agricultural and industrial sectors [102,103]. In addition, by repurposing waste, companies can lower disposal expenses and mitigate the risks associated with environmental regulations [104,105], minimizing the ecological footprint of agro-industrial operations by reducing landfill burden and associated greenhouse gas emissions while promoting sustainable resource management [106].

Waste reduction and the valorization of by-products are essential strategies for strengthening sustainability in the industry. With increasing environmental awareness, several sectors have rethought the destination of their waste. In agribusiness, for example, plant residues represent a significant portion of by-products, and their high volume can cause serious environmental impacts. The accumulation of organic waste in landfills brings significant environmental challenges. The slow degradation of these wastes occupies large volumes and releases greenhouse gases, such as methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O), that contribute to global warming [107,108]. In the specific case of protein waste, it is estimated that between 15 and 750 kg of carbon dioxide are emitted per kilogram of wasted edible protein [109,110].

The proper disposal and the reuse of waste are essential for the economy and environmental preservation. The circular economy aims to add value to waste by diverting it from methods such as environmental disposal, incineration, or landfill. This concept introduces a new perspective on the reuse and valorization of agro-industrial waste, reducing the need for additional natural resources [111].

In this way, transforming this waste into new products presents a promising opportunity to mitigate environmental damage and generate economic value. An effective strategy is the recovery of bioactive compounds from plant waste, which can be incorporated into the food, cosmetics, and pharmaceutical industries [112,113].

By converting plant waste into high-value-added ingredients, companies not only open up new sources of revenue but also reduce the costs related to the final disposal of waste. This practice reduces dependence on the extraction of new raw materials, contributing to the preservation of ecosystems, water, and energy resources. Thus, a business model based on the circular economy drives innovation and competitiveness, creating a virtuous cycle of sustainable production [114].

6. Conclusions

Plant residues and by-products contain a wide diversity of bioactive molecules with significant potential for application in the cosmetic industry. These compounds, including antioxidants, polyphenols, vitamins, amino acids, and peptides, provide functional benefits to cosmetic formulations, such as moisturizing, anti-inflammatory, and antiaging effects.

The upcycling of residual materials that would otherwise be discarded or undervalued adds economic value to these by-products and represents an important step toward strengthening the circular economy. This process significantly reduces the demand for virgin raw materials, thereby minimizing the environmental impacts associated with the extraction of new natural resources. Moreover, it contributes to the mitigation of greenhouse gas emissions and, consequently, enhances the sustainability of the sector.