Brewer's spent grain: a valuable feedstock for industrial applications

Integrated Metabolomics and Metagenomics Unveiled Biomarkers of Antioxidant Potential in Fermented Brewer's Grains

About one-third of the global food supply is wasted. Brewers' spent grain (BSG), being produced in enormous amounts by the brewery industry, possesses an eminence nutritional profile, yet its recycling is often neglected for multiple reasons. We employed integrated metagenomics and metabolomics techniques to assess the effects of enzyme treatments and Lactobacillus fermentation on the antioxidant capacity of BSG. The biotreated BSG revealed improved antioxidant capability, as evidenced by significantly increased (p < 0.05) radical scavenging activity and flavonoid and polyphenol content. Untargeted metabolomics revealed that Lactobacillus fermentation led to the prominent synthesis (p < 0.05) of 15 novel antioxidant peptides, as well as significantly higher (p < 0.05) enrichment of isoflavonoid and phenylpropanoid biosynthesis pathways. The correlation analysis demonstrated that Lactiplantibacillus plantarum exhibited strong correlation (p < 0.05) with aucubin and carbohydrate-active enzymes, namely, glycoside hydrolases 25, glycosyl transferases 5, and carbohydrate esterases 9. The fermented BSG has potential applications in the food industry as a culture medium, a functional food component for human consumption, and a bioactive feed ingredient for animals.

Green Methods to Recover Bioactive Compounds from Food Industry Waste: A Sustainable Practice from the Perspective of the Circular Economy

The worrying and constant increase in the quantities of food and beverage industry by-products and wastes is one of the main factors contributing to global environmental pollution. Since this is a direct consequence of continuous population growth, it is imperative to reduce waste production and keep it under control. Re-purposing agro-industrial wastes, giving them new life and new directions of use, is a good first step in this direction, and, in global food production, vegetables and fruits account for a significant percentage. In this paper, brewery waste, cocoa bean shells, banana and citrus peels and pineapple wastes are examined. These are sources of bioactive molecules such as polyphenols, whose regular intake in the human diet is related to the prevention of various diseases linked to oxidative stress. In order to recover such bioactive compounds using more sustainable methods than conventional extraction, innovative solutions have been evaluated in the past decades. Of particular interest is the use of deep eutectic solvents (DESs) and compressed solvents, associated with green techniques such as microwave-assisted extraction (MAE), ultrasonic-assisted extraction (UAE), pressurized liquid extraction (PLE) and pulsed-electric-field-assisted extraction (PEF). These novel techniques are gaining importance because, in most cases, they allow for optimizing the extraction yield, quality, costs and time.

Evaluating the application of an arabinoxylan-rich fraction from brewers' spent grain as a release modifier of drugs

This study evaluated the possible use of a fraction of brewers' spent grain rich in arabinoxylans (BSG-AX) as an excipient that modifies the release of class III drugs (Biopharmaceutics Classification System), by determining the release profile of metformin hydrochloride (MH), in a water medium. The cumulative percentage of MH release showed the best linear fit when modeled with the cumulative distribution function (CDF) of the Weibull distribution (R2 = 0.993 ± 0.001). According to the Korsmeyer-Peppas model, the first stage of MH release is regulated by a super case-II transport mechanism controlled by the expansion and relaxation of BSG-AX. Finally, with the Hixson-Crowell model, a release rate (k HC ) of 0.350 ± 0.026 h - 1 3 was obtained (R2 = 0.996 ± 0.007). BSG-AX constitutes a suitable material for producing prolonged drug release vehicles; however, additional research is required to provide a better encapsulation of the active ingredients to ensure their optimal applicability and performance.

Green biocatalyst for decolorization of azo dyes from industrial wastewater: Coriolopsis trogii 2SMKN laccase immobilized on recycled brewer's spent grain

This study presents an innovative approach for the reuse and recycling of waste material, brewer's spent grain (BSG) for creating a novel green biocatalyst. The same BSG was utilized in several consecutive steps: initially, it served as a substrate for the cultivation and production of laccase by a novel isolated fungal strain, Coriolopsis trogii 2SMKN, then, it was reused as a carrier for laccase immobilization, aiding in the process of azo dye decolorization and finally, reused as recycled BSG for the second successful laccase immobilization for six guaiacol oxidation, contributing to a zero-waste strategy. The novel fungal strain produced laccase with a maximum activity of 171.4 U/g after 6 days of solid-state fermentation using BSG as a substrate. The obtained laccase exhibited excellent performance in the decolorization of azo dyes, both as a free and immobilized, at high temperatures, without addition of harmful mediators, achieving maximum decolorization efficiencies of 99.0%, 71.2%, and 61.0% for Orange G (OG), Congo Red, and Eriochrome Black T (EBT), respectively. The immobilized laccase on BSG was successfully reused across five cycles of azo dye decolorization process. Notably, new green biocatalyst outperformed commercial laccase from Aspergillus spp. in the decolorization of OG and EBT. GC-MS and LC-MS revealed azo-dye degradation products and decomposition pathway. This analysis was complemented by antimicrobial and phytotoxicity tests, which confirmed the non-toxic nature of the degradation products, indicating the potential for safe environmental disposal.

High-Temperature Hydrothermal Extraction of Phenolic Compounds from Brewer's Spent Grain and Malt Dust Biomass Using Natural Deep Eutectic Solvents

Aligned with the EU Sustainable Development Goals 2030 (EU SDG2030), extensive research is dedicated to enhancing the sustainable use of biomass waste for the extraction of pharmaceutical and nutritional compounds, such as (poly-)phenolic compounds (PC). This study proposes an innovative one-step hydrothermal extraction (HTE) at a high temperature (120 °C), utilizing environmentally friendly acidic natural deep eutectic solvents (NADESs) to replace conventional harmful pre-treatment chemicals and organic solvents. Brewer's spent grain (BSG) and novel malt dust (MD) biomass sources, both obtained from beer production, were characterized and studied for their potential as PC sources. HTE, paired with mild acidic malic acid/choline chloride (MA) NADES, was compared against conventional (heated and stirred maceration) and modern (microwave-assisted extraction; MAE) state-of-the-art extraction methods. The quantification of key PC in BSG and MD using liquid chromatography (HPLC) indicated that the combination of elevated temperatures and acidic NADES could provide significant improvements in PC extraction yields ranging from 251% (MD-MAC-MA: 29.3 µg/g; MD-HTE-MA: 103 µg/g) to 381% (BSG-MAC-MA: 78 µg/g; BSG-HTE-MA: 375 µg/g). The superior extraction capacity of MA NADES over non-acidic NADES (glycerol/choline chloride) and a traditional organic solvent mixture (acetone/H2O) could be attributed to in situ acid-catalysed pre-treatment facilitating the release of bound PC from lignin-hemicellulose structures. Qualitative 13C-NMR and pyro-GC-MS analysis was used to verify lignin-hemicellulose breakdown during extraction and the impact of high-temperature MA NADES extraction on the lignin-hemicellulose structure. This in situ acid NADES-catalysed high-temperature pre-treatment during PC extraction offers a potential green pre-treatment for use in cascade valorisation strategies (e.g., lignin valorisation), enabling more intensive usage of available biomass waste stream resources.

Use of Residual Malt from an Artisanal Beer Brewing Process in the Biosynthesis of Silver Nanoparticles Mediated by Nucleating and Structure-Directing Agents

Biosynthesized silver nanoparticles (AgNPs) are widely used in varied applications, which are morphology dependent. Consequently, a morphology-controlled synthesis is mandatory. Although there are several studies focused on the plant extract-based biosynthesis of metallic nanoparticles, the use of extracts obtained from agro-wastes is scant. Furthermore, information regarding morphology modification through the use of additional agents is even more scarce. Thus, in this study, AgNPs were synthesized using a malt extract (ME) obtained from an artisanal beer brewing process residue. Additionally, sodium chloride (NaCl), gum arabic (GA), and talc (T) were used in an attempt to modify the morphology of AgNPs. XRD, DLS, SEM, and TEM results demonstrate that stable AgNPs of different sizes and shapes were synthesized. FTIR, HPLC analysis, and the quantification of total proteins, free amino acids, reducing sugars, and total polyphenols before and after AgNPs synthesis showed that ME biomolecules allowed them to act as a source of reducing and stabilizing agents. Therefore, this study provides evidence that ME can be successfully used to biosynthesize AgNPs. Additionally, the antibacterial activity of AgNPs against Gram-negative and Gram-positive bacteria was evaluated. Results indicate that AgNPs show a higher antibacterial activity against Gram-positive bacteria.

Successive process for efficient biovalorization of Brewers' spent grain to lignocellulolytic enzymes and lactic acid production through simultaneous saccharification and fermentation

This study aimed to increase the value of brewers' spent grain (BSG) by using it as feedstock to produce lignocellulolytic enzymes and lactic acid (LA). Twenty-two fungal strains were screened for lignocellulolytic enzyme production from BSG. Among them, Trichoderma sp. showed the highest cellulase activity (35.84 ± 0.27 U/g-BSG) and considerably high activities of xylanase (599.61 ± 23.09 U/g-BSG) and β-glucosidase (16.97 ± 0.77 U/g-BSG) under successive solid-state and submerged fermentation. The processes were successfully scaled up in a bioreactor. The enzyme cocktail was recovered and characterized. The maximum cellulase and xylanase activities were found at pH 5.0 and 50 °C, and the activities were highly stable at pH 4-8 and 30-50 °C. The enzyme cocktail was applied in simultaneous saccharification and fermentation of acid-pretreated BSG for LA production. The maximum LA obtained was 59.3 ± 1.0 g/L. This study has shown the efficient biovalorization of BSG, and this approach may also be applicable to other agro-industrial wastes.

Substitution of fishmeal: Highlights of potential plant protein sources for aquaculture sustainability

High protein content, excellent amino acid profile, absence of anti-nutritional factors (ANFs), high digestibility and good palatability of fishmeal (FM), make it a major source of protein in aquaculture. Naturally derived FM is at risk due to an increase in its demand, unsustainable practices, and price. Thus, there is an urgent need to find affordable and suitable protein sources to replace FM. Plant protein sources are suitable due to their widespread availability and low cost. However, they contained certain ANFs, deficiency of some amino acids, low nutrient bioavailability and poor digestibility due to presence of starch and fiber. These unfavourable characteristics make them less suitable for feed as compared to FM. Thus, these potential challenges and limitations associated with various plant proteins have to be overcome by using different methods, i.e. enzymatic pretreatments, solvent extraction, heat treatments and fermentation, that are discussed briefly in this review. This review assessed the impacts of plant products on growth performance, body composition, flesh quality, changes in metabolic activities and immune response of fishes. To minimize the negative effects and to enhance nutritional value of plant products, beneficial functional additives such as citric acid, phytase and probiotics could be incorporated into the plant-based FM. Interestingly, these additives improve growth of fishes by increasing digestibility and nutrient utilization of plant based feeds. Overall, this review demonstrated that the substitution of fishmeal by plant protein sources is a plausible, technically-viable and practical option for sustainable aquaculture feed production.

A critical review on the biotechnological potential of Brewers' waste: Challenges and future alternatives

In order to comply with the stringent discharge guidelines issued by governmental organizations to protect the ecosystem, the substantial amounts of effluent and sturdy wastes produced by the beer brewing process need to be discarded or handled in the most affordable and secure manner. Huge quantities of waste material released with each brew bestow a significant opportunity for the brewing sector to move towards sustainability. The concept of circular economy and the development of technological advancements in brewery waste processing have spurred interest to valorize brewery waste for implementation in various sectors of medical and food science, industrial science, and many more intriguing fields. Biotechnological methods for valorizing brewery wastes are showing a path towards green chemistry and are feasible and advantageous to environment. The study unfolds most recent prospectus for brewery waste usage and discusses major challenges with brewery waste treatment and valorization and offers suggestions for further work.

Rice Husk, Brewer's Spent Grain, and Vine Shoot Trimmings as Raw Materials for Sustainable Enzyme Production

Solid by-products with lignocellulosic structures are considered appropriate substrates for solid-state fermentation (SSF) to produce enzymes with diverse industrial applications. In this work, brewer's spent grain (BSG), rice husk (RH), and vine shoot trimmings (VSTs) were employed as substrates in SSF with Aspergillus niger CECT 2088 to produce cellulases, xylanases, and amylases. The addition of 2% (NH4)2SO4 and 1% K2HPO4 to by-products had a positive effect on enzyme production. Substrate particle size influenced enzyme activity and the overall highest activities were achieved at the largest particle size (10 mm) of BSG and RH and a size of 4 mm for VSTs. Optimal substrate composition was predicted using a simplex centroid mixture design. The highest activities were obtained using 100% BSG for β-glucosidase (363 U/g) and endo-1,4-β-glucanase (189 U/g), 87% BSG and 13% RH for xylanase (627 U/g), and 72% BSG and 28% RH for amylase (263 U/g). Besides the optimal values found, mixtures of BSG with RH or VSTs proved to be alternative substrates to BSG alone. These findings demonstrate that SSF bioprocessing of BSG individually or in mixtures with RH and VSTs is an efficient and sustainable strategy to produce enzymes of significant industrial interest within the circular economy guidelines.

Preparation of potential organic fertilizer rich in γ-polyglutamic acid via microbial fermentation using brewer's spent grain as basic substrate

Brewer's spent grain (BSG) is a main byproduct of the beer industry. BSG is rich in a variety of nutrients, and the search for its effective, high-value utilization is ongoing. Environmental probiotic factor γ-PGA was produced by fermenting Bacillus subtilis with BSG substrate and the fermenting grain components were analyzed. The γ-PGA yield reached 31.58 ± 0.21 g/kg of BSG. Gas chromatography-mass spectrometry and non-targeted metabolomics analyses revealed 73 new volatile substances in the fermenting grains. Furthermore, 2,376 metabolites were upregulated after fermentation and several components were beneficial for plant growth and development (such as ectoine, acetyl eugenol, L-phenylalanine, niacin, isoprene, pantothenic acid, dopamine, glycine, proline, jasmonic acid, etc). These results show that it is possible to synthesize adequate amounts of γ-PGA for use as a functional fertilizer.

Life-cycle assessment as a prospection stage for the biochemical methane potential of pretreated lignocellulosic biomass

The goal of neutrality in greenhouse gas emissions has intensified the search for renewable fuels. However, it is crucial to ensure sustainability of new technologies before proposing their implementation. This study proposes the use of life-cycle assessment (LCA) as an intermediary tool to identify critical hotspots in the exploration of hydrothermal pretreatment of lignocellulosic biomass, followed by biochemical methane potential assessment. Brewer s spent grain (BSG) was investigated, and laboratory-scale results were applied in an attributional assessment model with business-as-usual serving as the baseline. The LCA revealed that assumptions made in the lab could pose limitations. In Brazil, the two-stage co-digestion of pretreated hydrothermal BSG showed promising prospects, with a reduction to a new value of -54 kg CO2-eq Ton-1 BSG compared to 90 kg CO2-eq Ton-1 BSG in the business-as-usual scenario. Within the top ten global beer producing countries, only Brazil and Spain demonstrated potential for exploring this proposal.

The Rheology and Textural Properties of Bakery Products Upcycling Brewers' Spent Grain

This study aimed to evaluate the rheological properties of doughs with 50% brewers' spent grain (BSG) derived from a rye-based (RBSG) and barley-based (BBSG) beer added, and the textural profile of the related baked products. Simple model systems using BSG flour mixed with water were studied. Two bakery products, focaccia and cookies, were made as food systems using BSG in a 1:1 ratio with wheat flour (WF). Their rheological properties and texture after baking were characterized. BSG-added dough exhibited viscoelastic properties with a solid gel-like behavior. The addition of BSG increased G' > G″ and decreased the dough flexibility. BSG addition in baked RBSG focaccia increased the hardness, gumminess, and chewiness by 10%, 9%, and 12%, respectively. BBSG cookies had a 20% increase in fracturability. A positive correlation was found between the rheological metrics of the dough and the textural parameters of BBSG-added cookies. PCA analysis revealed that complex viscosity, G', G″, and cohesiveness separated BBSG focaccia from RBSG focaccia and the control. Therefore, the rheological properties of BSG dough will have industrial relevance for 3D-printed customized food products with fiber. Adding RBSG and BBSG to selected foods will increase the up-cycling potential by combining techno-functional properties.

Potential of Nanocellulose as a Dietary Fiber Isolated from Brewer's Spent Grain

Steady growth in beer production is increasing the number of by-products named brewers' spent grain. Such by-products are a source of several components, where cellulose is usually present in high amounts. The aim of this study was to develop a protocol to obtain a mix of cellulose microfibers with an average diameter of 8-12 µm and cellulose nanoplatelets with an average thickness of 100 nm, which has several applications in the food industry. The process comprised one alkaline treatment followed by acid hydrolysis, giving a new mix of micro and nanocellulose. This mix was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and laser scanning microscopy corroborating the presence and measurements of the cellulose nanostructure, showing an aspect ratio of up to 500. Finally, we demonstrated that the administration of this new type of nanocellulose allowed us to control the weight of mice (feed intake), showing a significant percentage of weight reduction (4.96%) after 15 days compared with their initial weight, indicating the possibility of using this material as a dietary fiber.

A specific H2/CO2 consumption molar ratio of 3 as a signature for the chain elongation of carboxylates from brewer's spent grain acidogenesis

Brewer's spent grain (BSG) is an undervalorized organic feedstock residue composed of fermentable macromolecules, such as proteins, starch, and residual soluble carbohydrates. It also contains at least 50% (as dry weight) of lignocellulose. Methane-arrested anaerobic digestion is one of the promising microbial technologies to valorize such complex organic feedstock into value-added metabolic intermediates, such as ethanol, H₂, and short-chain carboxylates (SCC). Under specific fermentation conditions, these intermediates can be microbially transformed into medium-chain carboxylates through a chain elongation pathway. Medium-chain carboxylates are of great interest as they can be used as bio-based pesticides, food additives, or components of drug formulations. They can also be easily upgraded by classical organic chemistry into bio-based fuels and chemicals. This study investigates the production potential of medium-chain carboxylates driven by a mixed microbial culture in the presence of BSG as an organic substrate. Because the conversion of complex organic feedstock to medium-chain carboxylates is limited by the electron donor content, we assessed the supplementation of H₂ in the headspace to improve the chain elongation yield and increase the production of medium-chain carboxylates. The supply of CO₂ as a carbon source was tested as well. The additions of H₂ alone, CO₂ alone, and both H₂ and CO₂ were compared. The exogenous supply of H₂ alone allowed CO₂ produced during acidogenesis to be consumed and nearly doubled the medium-chain carboxylate production yield. The exogenous supply of CO₂ alone inhibited the whole fermentation. The supplementation of both H₂ and CO₂ allowed a second elongation phase when the organic feedstock was exhausted, which increased the medium-chain carboxylate production by 285% compared to the N₂ reference condition. Carbon- and electron-equivalent balances, and the stoichiometric ratio of 3 observed for the consumed H₂/CO₂, suggest an H₂- and CO₂-driven second elongation phase, converting SCC to medium-chain carboxylates without an organic electron donor. The thermodynamic assessment confirmed the feasibility of such elongation.

Protein recovery from brewery solid wastes

Brewing produces significant amounts of solid waste during the process: spent cereals (BSG), hops and spent yeast (BSY). These residues are sustainable sources of valuable nutrients and functional compounds like proteins, polyphenols, and polysaccharides. This review describes the three solid wastes and the different extraction techniques for protein recovery. The protein obtained can be used as a new source of non-animal protein or as a functional and bioactive ingredient. Particular attention was given to methods using conventional technologies (alkaline and ethanolic extraction) and more innovative approaches (enzymes, microwaves, ultrasound, pressurized liquids and sub-critical water extraction). Although the BSG is used in some industrial applications, studies in operating conditions, cost, energy efficiency, and product performance are still required to consolidate these solid wastes as a source of non-animal protein. The application of proteins is also an important question when choosing the extraction method.

Stabilization and Valorization of Beer Bagasse to Obtain Bioplastics

Beer bagasse is a residue produced in large quantities, though it is undervalued in the industry. Its high protein and polysaccharide content make it attractive for use in sectors such as the manufacture of bioplastics. However, its high water content makes it necessary to stabilize it before being considered as a raw material. The main objective of this work was to evaluate the stabilization of beer bagasse and the production of bioplastics from it. In this sense, different drying methods (freeze-drying and heat treatment at 45 and 105 °C) were studied. The bagasse was also characterized physicochemically to evaluate its potential. In addition, bagasse was used in combination with glycerol (plasticizer) to make bioplastics by injection molding, analyzing their mechanical properties, water absorption capacity and biodegradability. The results showed the great potential of bagasse, presenting a high content of proteins (18-20%) and polysaccharides (60-67%) after its stabilization, with freeze-drying being the most suitable method to avoid its denaturation. Bioplastics present appropriate properties for use in applications such as horticulture and agriculture.

Variability of Micro- and Macro-Elements in Anaerobic Co-Digestion of Municipal Sewage Sludge and Food Industrial By-Products

The main aim of this study was to evaluate the effect of the addition of selected industrial food wastes on the fate of micro- and macro-elements within an anaerobic digestion process (AD), as well as define the relationship between their content and AD efficiency. Orange peels, (OP), orange pulp (PL) and brewery spent grain (BSG) were used as co-substrates, while municipal sewage sludge (SS) was applied as the main component. The introduction of co-substrates resulted in improvements in feedstock composition in terms of macro-elements, with a simultaneous decrease in the content of HMs (heavy metals). Such beneficial effects led to enhanced methane production, and improved process performance at the highest doses of PL and BSG. In turn, reduced biogas and methane production was found in the three-component digestion mixtures in the presence of OP and BSG; therein, the highest accumulation of most HMs within the process was also revealed. Considering the agricultural application of all digestates, exceedances for Cu, Zn and Hg were recorded, thereby excluding their further use for that purpose.

Foaming properties are improved by interactions between brewer's spent grain proteins and carrageenans in aqueous solution

BACKGROUND

Foaming properties and macromolecular interactions in solution among brewer's spent grain proteins (CP) and iota and lambda carrageenans (i-CG and l-CG, respectively) as a function of aqueous medium pH (2-6) and protein-polysaccharide ratio, R_CP:CG (1:1, 2:1 and 4:1), were studied. At these conditions, the CP colloidal stability was favored by the formation of soluble electrostatic complexes with CG. Fluorescence (intrinsic and extrinsic) spectroscopy and dynamic light scattering techniques, including particle size and ζ-potential analysis, were applied to know the phase behavior of the biopolymer systems. The bubbling method was used to produce foams, and the foam expansion (%) and half-life time (t_1/2 ) were determined.

RESULTS

Both CG promoted an increased Trp fluorescence emission depending on the pH, suggesting conformational changes in CP. The CG in mixed systems produced a significant decrease in the extrinsic fluorescence intensity, mainly at low pH values, highlighting a reduction in CP surface hydrophobicity. At the examined pH range, the ζ-potential values for mixed-systems were negative, and their magnitudes were intermediate between CP and CG, revealing the associative electrostatic nature of biopolymer interactions, which were dependent on the R_CP:CG . The particle size analysis confirmed the formation of soluble electrostatic complexes in solution. Finally, using i-CG at pH 2 or 3 and 2:1 R_CP:CG , the best foaming properties for mixed systems were observed.

CONCLUSION

The formation of electrostatic complexes with a compact assembly among biopolymers, high negative net charge, and colloidal stability convert the CP-CG mixed solutions into promising biopolymer systems for food foams production. © 2022 Society of Chemical Industry.

Brewer's Spent Grain, Coffee Grounds, Burdock, and Willow-Four Examples of Biowaste and Biomass Valorization through Advanced Green Extraction Technologies

This paper explores the transformation of biowastes from food industry and agriculture into high-value products through four examples. The objective is to provide insight into the principles of green transition and a circular economy. The first two case studies focus on the waste generated from the production of widely consumed food items, such as beer and coffee, while the other two examine the potential of underutilized plants, such as burdock and willow, as sources of valuable compounds. Phenolic compounds are the main target in the case of brewer's spent grain, with p-coumaric acid and ferulic acid being the most common. Lipids are a possible target in the case of spent coffee grounds with palmitic (C16:0) and linoleic (C18:2) acid being the major fatty acids among those recovered. In the case of burdock, different targets are reported based on which part of the plant is used. Extracts rich in linoleic and oleic acids are expected from the seeds, while the roots extracts are rich in sugars, phenolic acids such as chlorogenic, caffeic, o-coumaric, syringic, cinnamic, gentisitic, etc. acids, and, interestingly, the high-value compound epicatechin gallate. Willow is well known for being rich in salicin, but picein, (+)-catechin, triandrin, glucose, and fructose are also obtained from the extracts. The study thoroughly analyzes different extraction methods, with a particular emphasis on cutting-edge green technologies. The goal is to promote the sustainable utilization of biowaste and support the green transition to a more environmentally conscious economy.

Trends and innovations in the formulation of plant-based foods

Globally, the production, distribution, sale and consumption of plant-based foods (PBFs) are on the increase due to heightened consumer awareness, a growing demand for clean label products, widespread efforts to promote and embrace sustainable practices, and ethical concerns over animal-derived counterparts. This has led to the exploration of several strategies by researchers and the food industry to develop alternative milk, cheese, meat, and egg products from various plant-based sources using technologies such as precision fermentation (PF), scaffolding, extrusion, and muscle fibre simulation. This work explores current alternative protein sources and PBFs, production trends, innovations in formulation, nutritional quality, as well as challenges restricting full utilization and other limitations. However, PBFs have several limitations which constrain their acceptance, including the beany flavour of legumes, concerns about genetically modified foods, cost, nutritional inadequacies associated micronutrient deficiencies, absence of safety regulations, and the addition of ingredients that are contrary to their intended health-promoting purpose. The review concludes that investing in the development of PBFs now, has the potential to facilitate a rapid shift to large scale consumption of sustainable and healthy diets in the near future.

Graphical Abstract

Characterization of brewer's spent grain extracts by tandem mass spectrometry and HPLC‐DAD : Ferulic acid dehydrodimers, phenolamides, and oxylipins

Brewer's spent grain (BSG) is a major by-product of the brewing industry which is generated in high amounts. In recent years, sustainable food production has become more and more important. BSG mainly used as cattle feed has gained high interest due to not only its valuable ingredients such as fiber and proteins but also secondary metabolites remaining in BSG after the brewing process and known for many biological effects. In the present study, various methods were applied, such as acetone extraction (A), alkaline hydrolysis followed by ethyl acetate extraction (HE), and acetone extraction of alkaline hydrolysis residue (HA). Compounds present in the respective bioactive extracts were characterized by mass spectrometry to identify the active compounds. Various hydroxycinnamic acid derivatives as well as oxylipins and some dicarboxylic acids, such as azelaic acid, were present in HE and HA extracts. In contrast, some catechins and phenolamides, such as numerous hordatines, as well as oxylipins and phospholipids were detected in A extracts. Quantification using HPLC-DAD revealed hordatine contents up to 172.2 ± 2.1 μg p-coumaric acid equivalents/mg extract. Hydroxycinnamic acid derivatives content accounted for up to 48% of the total extract (HE extracts) but only around 3% of the total HA extracts. In summary, all extracts contained secondary plant metabolites belonging to different classes, ranging from hydroxycinnamic acids to phenolamides, such as not only hordatines but also oxylipins, which were identified for the first time in BSG.

Subcritical water pretreatment enhanced methane-rich biogas production from the anaerobic digestion of brewer's spent grains

ABSTRACTThis study evaluated the effectiveness of a semi-continuous flow-through subcritical water hydrolysis (SWH) pretreatment of brewer's spent grains (BSG) for subsequent application in the anaerobic digestion (AD) process. BSG pretreatment was conducted at 160 °C and 15 MPa with a flow rate of 10 mL water min-1 and 15 g water g-1 BSG. The results revealed that SWH attacked the hemicellulose structure, releasing arabinose (46.54 mg g-1) and xylose (39.90 mg g-1) sugars, and proteins (34.89 mg g-1). The start-up of anaerobic reactors using pretreated BSG (747.71 L CH4 kg-1 TVS) increased the methane yield compared with the reactor without pretreatment (53.21 L CH4 kg-1 TVS). For the process with pretreatment, the generation of electricity (134 kWh t-1 BSG) and heat (604 MJ t-1) are responsible for the mitigation of 43.90 kg CO2 eq t-1 BSG. The adoption of SWH as an eco-friendly pretreatment of biomass for AD could be a technological route to increase methane-rich biogas and bioenergy production, supporting the circular economy transition by reducing the carbon footprint of the beer industry.

Barley in the Production of Cereal-Based Products

Barley (Hordeum vulgare L.) is unjustly neglected today as a food grain. Interest in the use of barley in the food industry has increased recently. The reason for this is its content of dietary fibre, especially β-glucan, which has been shown to reduce blood cholesterol and lower blood sugar levels. The main nutritional components of barley and barley products, besides the mentioned β-glucan, are starch, sugar, proteins, fat and ash. Although not common in the production of bakery products, barley can be very easily involved in the production of the same products, and such products have improved nutritional characteristics and acceptable sensory characteristics, which make them desirable. Barley has great potential for use in a wide range of cereal-based foods as a partial or full replacement for currently used grains (such as wheat, oats, rice and corn). This article provides basic and general information about the use of barley in food and the processing of barley grains for use in the manufacturing of cereal-based products, with particular attention to the use of barley in the manufacturing of bread (flatbread and leavened bread), noodles and pasta, muffins and cakes and cookies and biscuits.

Upcycled foods: A nudge toward nutrition

One of the aims of the United Nations Sustainable Development Goals (SDG) is to end hunger and ensure access by all people to safe, nutritious, and sufficient food all year round. An obvious synergy exists between the second SDG “Zero Hunger” and SDG target 12.3 which focuses on halving food waste and reducing food losses. In addition to helping improve global food security, reducing food waste provides financial and environmental benefits. Upcycling food is a technical solution for food waste reduction that retains the nutritional and financial value of food by-products. However, many of the upcycled foods produced are discretionary foods such as biscuits, crackers, and other snack food that are not part of a healthy dietary pattern, and should only be eaten sometimes in small amounts. Given the importance of ensuring a sustainable healthy diet, this paper discusses opportunities for upcycled food manufacturers to produce more nutritious products.

Biorefinery of Brewery Spent Grain by Solid-State Fermentation and Ionic Liquids

Novel environmentally friendly pretreatments have been developed in recent years to improve biomass fractionation. Solid-state fermentation (SSF) and treatment with ionic liquids show low environmental impact and can be used in biorefinery of biomass. In this work, these processes were assessed with brewery spent grain (BSG). First, BSG was used as a substrate to produce cellulases and xylanases by SSF with the fungi Aspergillus brasiliensis CECT 2700 and Trichoderma reesei CECT 2414. Then, BSG was pretreated with the ionic liquid [N₁₁₁₂OH][Gly] and hydrolyzed with the crude enzymatic extracts. Results showed that SSF of BSG with A. brasiliensis achieved the highest enzyme production; meanwhile, the pretreatment with ionic liquids allowed glucan and xylan fractions to increase and reduce the lignin content. In addition, a mixture of the extracts from both fungi in a ratio of 2.5:0.5 Aspergillus/Trichoderma (v/v) efficiently hydrolyzed the BSG previously treated with the ionic liquid [N₁₁₁₂OH][Gly], reaching saccharification percentages of 80.68%, 54.29%, and 19.58% for glucan, xylan, and arabinan, respectively. In conclusion, the results demonstrated that the BSG biorefinery process developed in this work is an effective way to obtain fermentable sugar-containing solutions, which can be used to produce value-added products.

Sustainable plant-based ingredients as wheat flour substitutes in bread making

Bread as a staple food has been predominantly prepared from refined wheat flour. The world’s demand for food is rising with increased bread consumption in developing countries where climate conditions are unsuitable for wheat cultivation. This reliance on wheat increases the vulnerability to wheat supply shocks caused by force majeure or man-made events, in addition to negative environmental and health consequences. In this review, we discuss the contribution to the sustainability of food systems by partially replacing wheat flour with various types of plant ingredients in bread making, also known as composite bread. The sustainable sources of non-wheat flours, their example use in bread making and potential health and nutritional benefits are summarized. Non-wheat flours pose techno-functional challenges due to significantly different properties of their proteins compared to wheat gluten, and they often contain off-favor compounds that altogether limit the consumer acceptability of final bread products. Therefore, we detail recent advances in processing strategies to improve the sensory and nutritional profiles of composite bread. A special focus is laid on fermentation, for its accessibility and versatility to apply to different ingredients and scenarios. Finally, we outline research needs that require the synergism between sustainability science, human nutrition, microbiomics and food science.

Evaluating the potential applications of brewers' spent grain in biogas generation, food and biotechnology industry: A review

Breweries, as the major users of fossil fuels, are constantly under economic and environmental pressure to minimize energy consumption and residual management costs. Biogas generation from brewing wastes is a realistic solution for significantly reducing fossil fuel use. Brewers' spent grain (BSG) forms about eighty per cent of the total wastes from a brewing plant. BSG has a high cellulose and non-cellulosic polysaccharides content which makes it potential for biogas production. This paper reviews the potential applications of BSG as an alternative substrate for production of biogas and the recent achievements which have been attained in anaerobic digestion (AD) technology. The usability of BSG in diverse technologies including production of animal and human food and as a medium for growing microorganisms and enzymes is reviewed. The chemical processes involved in producing biogas from BSG are discussed.

Mixtures of mycotoxins, phytoestrogens and pesticides co-occurring in wet spent brewery grains (BSG) intended for dairy cattle feeding in Austria

Spent brewery grains (BSG) are the main by-product of beer production and are incorporated in rations of food-delivering animals, mainly dairy cows. Like other agricultural commodities, BSG can be contaminated by a broad spectrum of natural and synthetic undesirable substances, which can be hazardous to animal and human health as well as to the environment. The co-occurrence of mycotoxins, phytoestrogens, other fungal and plant secondary metabolites, along with pesticides, was investigated in 21 BSG samples collected in dairy farms in Austria. For this purpose, a validated multi-metabolite liquid chromatography/electrospray ionisation tandem mass spectrometry (LC/ESI-MS/MS) was employed. Metabolites derived from Fusarium, Aspergillus, Alternaria and pesticide residues, were ubiquitous in the samples. Zearalenone (ZEN), T-2 and HT-2 toxins were the only regulated mycotoxin detected, albeit at concentrations below the European guidance values for animal feeds. Ergot alkaloids, Penicillium-derived metabolites, and phytoestrogens had occurrence rates of 90, 48 and 29%, respectively. Penicillium metabolites presented the highest levels among the fungal compounds, indicating contamination during storage. Aflatoxins (AFs), ochratoxins and deoxynivalenol (DON) were not detected. Out of the 16 detected pesticides, two fungicides, ametoctradin (9.5%) and mandipropamid (14.3%) revealed concentrations exceeding their respective maximum residue level (MRL) (0.01 mg kg^-1) for barley in two samples. Although based on European guidance and MRL values the levels of the detected compounds probably do not pose acute risks for cattle, the impact of the long-time exposure to such mixtures of natural and synthetic toxicants on animal health and food safety are unknown and must be elucidated.

Regulation of the cecal microbiota community and the fatty liver deposition by the addition of brewers’ spent grain to feed of Landes geese

The effects of brewers’ spent grain (BSG) diets on the fatty liver deposition and the cecal microbial community were investigated in a total of 320 healthy 5-day-old Landes geese. These geese were randomly and evenly divided into 4 groups each containing 8 replicates and 10 geese per replicate. These four groups of geese were fed from the rearing stage (days 5–60) to the overfeeding stage (days 61–90). The Landes geese in group C (control) were fed with basal diet (days 5–90); group B fed first with basal diet in the rearing stage and then basal diet + 4% BSG in the overfeeding stage; group F first with basal diet + 4% BSG during the rearing stage and then basal diet in the overfeeding stage; and group W with basal diet + 4% BSG (days 5–90). The results showed that during the rearing stage, the body weight (BW) and the average daily gain (ADG) of Landes geese were significantly increased in groups F and W, while during the overfeeding stage, the liver weights of groups W and B were significantly higher than that of group C. The taxonomic structure of the intestinal microbiota revealed that during the overfeeding period, the relative abundance of Bacteroides in group W was increased compared to group C, while the relative abundances of Escherichia–Shigella and prevotellaceae_Ga6A1_group were decreased. Results of the transcriptomics analysis showed that addition of BSG to Landes geese diets altered the expression of genes involved in PI3K-Akt signaling pathway and sphingolipid metabolism in the liver. Our study provided novel experimental evidence based on the cecal microbiota to support the application of BSG in the regulation of fatty liver deposition by modulating the gut microbiota in Landes geese.

An Updated Review on Prebiotics: Insights on Potentials of Food Seeds Waste as Source of Potential Prebiotics

Prebiotics are a group of biological nutrients that are capable of being degraded by microflora in the gastrointestinal tract (GIT), primarily Lactobacilli and Bifidobacteria. When prebiotics are ingested, either as a food additive or as a supplement, the colonic microflora degrade them, producing short-chain fatty acids (SCFA), which are simultaneously released in the colon and absorbed into the blood circulatory system. The two major groups of prebiotics that have been extensively studied in relation to human health are fructo-oligosaccharides (FOS) and galactooligosaccharides (GOS). The candidature of a compound to be regarded as a prebiotic is a function of how much of dietary fiber it contains. The seeds of fruits such as date palms have been reported to contain dietary fiber. An increasing awareness of the consumption of fruits and seeds as part of the daily diet, as well as poor storage systems for seeds, have generated an enormous amount of seed waste, which is traditionally discarded in landfills or incinerated. This cultural practice is hazardous to the environment because seed waste is rich in organic compounds that can produce hazardous gases. Therefore, this review discusses the potential use of seed wastes in prebiotic production, consequently reducing the environmental hazards posed by these wastes.

Selenite and tellurite reduction by Aspergillus niger fungal pellets using lignocellulosic hydrolysate

The performance of Aspergillus niger pellets to remove selenite and tellurite from wastewater using batch and continuous fungal pelleted bioreactors was investigated. The acid hydrolysate of brewer's spent grain (BSG) was utilized by A. niger as the electron donor for selenite and tellurite reduction. The dilution of BSG hydrolysate using mineral medium had a positive effect on the selenite and tellurite removal efficiency with a 1:3 ratio giving the best efficiency. However, selenite and tellurite inhibited fungal growth with a 40.9% and 27.3% decrease in the A. niger biomass yield in the presence of 50 mg/L selenite and tellurite, respectively. The maximum selenite and tellurite removal efficiency using 25% BSG hydrolysate in batch incubations amounted to 72.8% and 99.5% Two fungal pelleted bioreactors were operated in continuous mode using BSG hydrolysate as the substrate. Both the selenite and tellurite removal efficiencies during steady state operation were > 80% with tellurite showing a maximum removal efficiency of 98.5% at 10 mg/L influent concentration. Elemental Se nanospheres for selenite and both Te nanospheres and nanorods for tellurite were formed within the fungal pellets. This study demonstrates the suitability BSG hydrolysate as a low cost carbon source for removal of selenite and tellurite using fungal pellet bioreactors.

Valorization of Brewery Waste through Polyhydroxyalkanoates Production Supported by a Metabolic Specialized Microbiome

Simple Summary

Raw brewers’ spent grain, a by-product of beer production, is produced at a large scale and is usually used as animal feed or is landfilled. However, its composition shows that this feedstock has the potential for other applications, such as bioplastics production (e.g., polyhydroxyalkanoates). In this way, the aim of this work was to assess the use of raw brewers’ spent grain for polyhydroxyalkanoates production, adding new value to this feedstock. The results confirm the potential of raw brewers’ spent grain to produce polyhydroxyalkanoates, as the population was enriched in the microorganisms able to accumulate these biopolymers. These results will contribute to society’s knowledge and competence via the development of a treatment process for brewery waste of both environmental (productive waste treatment) and economic interest (production of biopolymers), which will certainly attract its application to the brewery industry worldwide.

Abstract

Raw brewers’ spent grain (BSG), a by-product of beer production and produced at a large scale, presents a composition that has been shown to have potential as feedstock for several biological processes, such as polyhydroxyalkanoates (PHAs) production. Although the high interest in the PHA production from waste, the bioconversion of BSG into PHA using microbial mixed cultures (MMC) has not yet been explored. This study explored the feasibility to produce PHA from BSG through the enrichment of a mixed microbial culture in PHA-storing organisms. The increase in organic loading rate (OLR) was shown to have only a slight influence on the process performance, although a high selectivity in PHA-storing microorganisms accumulation was reached. The culture was enriched on various PHA-storing microorganisms, such as bacteria belonging to the Meganema, Carnobacterium, Leucobacter, and Paracocccus genera. The enrichment process led to specialization of the microbiome, but the high diversity in PHA-storing microorganisms could have contributed to the process stability and efficiency, allowing for achieving a maximum PHA content of 35.2 ± 5.5 wt.% (VSS basis) and a yield of 0.61 ± 0.09 Cmmol_PHA/Cmmol_VFA in the accumulation assays. Overall, the production of PHA from fermented BSG is a feasible process confirming the valorization potential of the feedstock through the production of added-value products.

In Vitro Digestibility of Minerals and B Group Vitamins from Different Brewers’ Spent Grains

Brewers’ spent grain (BSG), the main by-product of the brewing industry, is a rich source of minerals and water-soluble vitamins such as thiamine, pyridoxine, niacin, and cobalamin. Bioaccessibility through in vitro digestion is an important step toward the complete absorption of minerals and B group vitamins in the gastrointestinal system. Inductively coupled plasma optical emission spectrometry (ICP-OES) together with inductively coupled plasma quadrupole mass spectrometry (ICP-MS) was used for the quantification of the macro- and micro-minerals. An ultra-high performance liquid chromatography (UHPLC) system coupled with a diode array detector (DAD) was used for B group vitamin identification. Four different industrial BSG samples were used in the present study, with different percentages of malted cereals such as barley, wheat, and degermed corn. Calcium’s bioaccessibility was higher in the BSG4 sample composed of 50% malted barley and 50% malted wheat (16.03%), while iron presented the highest bioaccessibility value in the BSG2 sample (30.03%) composed of 65% Pale Ale malt and 35% Vienna malt. On the other hand, vitamin B1 had the highest bioaccessibility value (72.45%) in the BSG3 sample, whilst B6 registered the lowest bioaccessibility value (16.47%) in the BSG2 sample. Therefore, measuring the bioaccessibilty of bioactive BSG compounds before their further use is crucial in assessing their bioavailability.

Emerging sources and applications of alternative proteins: An introduction

Food protein is an essential macronutrient. Even though daily per capita supply of protein has increased globally from 61g in 1961 to 81g in 2013, and most people in the developed world have sufficient protein intake from their diets, however, protein deficiencies continue to be pervasive globally. Protein deficiency is the single major factor responsible for impaired growth and suboptimal health worldwide. Animal proteins are high quality and contain adequate and balanced amino acids, animal protein production however is inefficient and resource intensive. Alternative proteins are expected to provide the solution to meet the growing protein demand within the environmental limits. Alternative proteins include proteins from plants (i.e., grains, legumes, pulse, and nuts), fungus (i.e., mushrooms), algae, insects and cultured (lab-grown) meat that can be used to replace conventional animal proteins. Major concerns for human consumption of alternative proteins are inferior organoleptic properties, consumer acceptability, affordability, and sustainability. There is a need to develop culturally diversified alternative proteins to mitigate global protein malnutrition. Food proteins are also found applications in biomaterials and as a source of bioactive peptides.

Potential for the valorisation of brewer's spent grains: A case study for the sequential extraction of saccharides and lignin

This study highlights the possibility of using brewers' grains (BSGs) for the successive extraction of the main lignocellulosic biopolymers, namely, cellulose, hemicelluloses and lignin. An exhaustive chemical characterisation revealed a variability of composition in distinct batches of BSGs, depending on their origin and the brewing process used. In particular, the protein content can vary from 13wt% to 23wt%, which is accompanied by a change in the hemicelluloses content from 9% to 23% (in the samples of our study). By applying a two-step aqueous treatment, involving an acid (1.25% v/v aq. H₂SO₄) and a base (3% w/v aq. NaOH) at a temperature of 120°C and fixed reaction time of a few tens of minutes (15-90 minutes), more than 80% of hemicelluloses could be recovered. Cellulose could be isolated at more than 68%, while a high purity lignin could be recovered from a lignin-rich fraction (70wt%). Our work also suggests that the variability of the chemical composition of these BSGs is a hindrance to achieving process standardisation and large-scale exploitation. The pooling of various materials is therefore not a recommended option, and the preliminary chemical analysis of the composition is therefore a prerequisite for an efficient extraction process.

Development of Sustainable Biorefinery Processes Applying Deep Eutectic Solvents to Agrofood Wastes

The growing demand for renewable energies and the application of sustainable and economically viable biorefinery processes have increased the study and application of lignocellulosic biomass. However, due to lignocellulosic biomass recalcitrance hindering its efficient utilization, the pretreatment in the biorefinery is an essential stage for success in the process. Therefore, Deep Eutectic Solvent (DES) has emerged as a promising green pretreatment. During this study, the effect of choline chloride [ChCl]:glycerol and [ChCl]:urea on sugarcane bagasse and brewery bagasse is evaluated. Results have demonstrated that using [ChCl]:glycerol in SCB reduced about 80% and 15% for acid-soluble lignin and Klason lignin, respectively, and improved efficiency on saccharification yields, achieving conversions of 60, 80, and 100% for glucan, xylan, and arabinan, correspondingly. In the case of BSG saccharification yields, about 65% and 98% are attained for glucan and xylan, respectively, when [ChCl]:glycerol was employed. These results confirm the effectiveness and facility of DES pretreatment as a suitable method that can improve the biorefinery processes.

Valorisation of brewer's spent grain flour (BSGF) through wheat-maize-BSGF composite flour bread: optimization using D-optimal mixture design

Inclusion of brewer's spent grain flour (BSGF) in food formulations has been reported to have nutritional and health benefits due to the contents like, protein, fibre and phenolic compounds. Bread has been used as common vehicle for functional and nutritive ingredients due to its wide consumption. Several studies attempted to incorporate BSGF flour in baked products. Studies also have reported on the application of maize flour in bread and baked products. However, there is limited information on the possibility of producing bread from composite flour using BSGF with other widely consumed cereals like maize together with wheat flour. The study investigated the optimization of bread recipe made from wheat flour, maize flour and BSGF in order to attain optimal physicochemical and sensory attributes using D-optimal mixture design. A total of 16 runs were formulated using design expert software. The blend proportions of wheat, maize and BSGF had a significant (p < 0.05) influence on bread specific volume, volume and density. Increase in BSGF proportion decreased the specific volume and volume whereas the loaf density increased. The specific volume increased with increase in wheat flour proportion. The combination of high levels of BSGF and maize, however, brought about a slight increase in specific volume compared to combinations of low levels of BSGF and maize flour. The fibre, protein and ash content of bread significantly (p < 0.05) increased with increase in BSGF and maize proportion whereas the effect of maize flour was less pronounced compared to BSGF. The sensory attributes including colour, taste, flavour, texture and overall acceptability were significantly (p < 0.05) reduced with increase in BSGF and maize flour content. Using the optimization criteria where all sensory attributes have to be at least “like slightly” intensity, maximized, specific volume, fiber and protein, that the best results were found between 73 to 87% of wheat, 9–20% maize, and 0–11% BSGF based on graphical optimization. Numerical optimization indicated that best results were using combination of 65% wheat, 20% maize flour, and 15% BSGF with a desirability value of 0.524. According to the results of the study, BSGF can be incorporated up 10% and maize flour up to 20% obtain an acceptable product.

Study of the influence of exogenous fibrolytic enzyme additive on chemical composition, fermentation characteristics, and nutritional value of brewer's spent grain

This study explores the influence of different doses of two exogenous fibrolytic enzyme (EFE) additives (liquid (EFE₁: 1, 2, and 4 μΙ/g DM (dry matter)) and powder (EFE₂: 1, 2, and 4 mg/g DM)) on the chemical composition, fermentation characteristics, and nutritional value of brewer's spent grain (BSG). The results indicate that EFE₁ at low doses does not affect the chemical composition, fermentation characteristics, and the nutritional value of BSG. The medium dose EFE₁ decreases the fiber compound but increases the nonfiber carbohydrates (NFC) and soluble dry matter. Also, this dose modified the fermentation of BSG by increasing the amount of gas and its fermentation rate and decreasing the time between the inoculation and start of fermentation. Therefore, it increases the digestibility, metabolizable energy, net energy‐lactation (NE_L), total volatile fatty acids, and the microbial crude protein production of BSG. The high dose of EFE₁ decreases the fiber compound and increases the nonfiber carbohydrates and soluble dry matter; however, it also decreases the potential of gas production and does not affect the nutritional value of BSG. For EFE₂, all the doses do not modify the chemical composition, fermentation characteristics, and the nutritional value of BSG. These results suggest that the effectiveness of EFE varied, depending on the type of EFE and dose. Increase in the nutritional value of BSG by EFE₁ at the medium dose can encourage breeders to use these wastes as feed at low cost in cow nutrition.

The Use of Brewer’s Spent Grain after Beer Production for Energy Purposes

The aim of this study was to assess the possibilities to use brewer’s spent grains (BSGs) left over from beer production for energy purposes, and to determine its calorific value and chemical composition. The research materials were samples of wet spent grain from a brewery in Poland. Three samples, that are different in ingredient composition, were examined. The examined samples of BSGs were characterised by humidity that is typical for this product (approx. 77–80%). Convective drying of the spent grain contributed to a reduction in the water content in the biomass to below 10%. Samples of dry spent grain that were examined contained a similar amount of ash (3.8–4.1% d.m.) and organic matter (91.0–91.9% d.m.). All the examined spent grain samples demonstrated similar volatile matter content—approx. 77.8–78.7% d.m. and calorific value—approx. 15.6–15.9 MJ/kg. The estimated calorific value for wet samples (approx. 1.4–2.0 MJ/kg) indicated that it is necessary to lower water content in the biomass in order to improve its energy properties.

Bioelectrochemical Treatment Technology—The New Practical Approach for Wastewater Management and GHG Emissions Reduction

This study presents BioElectrochemical Treatment Technology (BETT) as a new wastewater management solution toward the Net-Zero future. The results reported herein were collected from a BETT pilot system installed at a large brewery in Los Angeles, CA, United States processing 0.6 m3. day-1 of raw brewery wastewater with a high content of fruit pulp. Removal of Chemical Oxygen Demand (COD), Total Suspended Solids (TSS) and protein in mg.L-1 per day or percentage were evaluated over 2 months of continuous operation of the Demo Unit. The GHG emissions associated with the power consumed, biomass produced, and carbon dioxide emitted were estimated and compared to aerobic and anaerobic solutions. It was demonstrated that BETT can process wastewater with higher organic load than most conventional anaerobic systems. The inflow COD loading varied between 48,550 mg/L to 116,200 mg/L, and BETT achieved up to 33% COD removal in 4-h HRT. The TSS removal reached values as high as 79% with incoming TSS concentrations up to 34,000 mg/L TSS. BETT did not directly generate methane and demonstrated 89 and 49% lower landfill methane emissions than aerobic and anaerobic technologies, respectively. The overall reduction in CO2 emissions, both direct and indirect, was estimated to be 85–90% compared to existing practices.

Arabinoxylans Release from Brewers’ Spent Grain Using Extrusion and Solid-State Fermentation with Fusarium oxysporum and the Antioxidant Capacity of the Extracts

Brewers’ spent grain (BSG) is the most abundant byproduct generated from the beer-brewing process. BSG is a material rich in hemicellulose, composed of arabinoxylans (AX). However, the high crosslinking of this material causes low availability of AX, for which it is necessary to apply different treatments. The objective of this research is to increase the release of arabinoxylans through solid-state fermentation with Fusarium oxysporum f. sp. lycopersici using extruded brewery spent grain. First, the BSG is subjected to two types of physical treatments: extrusion at 20% moisture, 200 rpm and 50 °C (BSGe), and blade milling (BSGm). The chemical composition is determined for each sample (BSG, BSGe and BSGm). Subsequently, the solid-state fermentation process (SSF) is carried out on each sample. The fermentation kinetics at 30 °C are monitored for 7 days. Once the SSF concludes, AX are extracted, and the purity of AX is determined by the phloroglucinol colorimetric assay. Finally, the total phenolic compounds, phenolic acids and antioxidant capacity by DPPH are quantified. No significant differences (p ≥ 0.05) in the protein, lipid, ash or total dietary fiber contents are found among the samples. No significant difference (p ≥ 0.05) in the content of soluble fiber is found, although BSGe and BSGm have higher values than BSG. On the other hand, the yields of soluble AX exhibit significant differences (p ≤ 0.05) among nonfermented samples (BSG, 0.03%; BSGm, 0.53%; BSGe, 0.70%) and with SSF (BSG, 2.95%; BSGm, 6.24%; and BSGe, 9.58%). In addition, the contents of free phenolic compounds and free phenolic acids and the percent inhibition of free extracts by 2,2-diphenyl-1-picrylhydrazyl (DPPH) differ significantly (p ≤ 0.05) between samples subjected to SSF and nonfermented samples. Therefore, extrusion and SSF treatment increase AX release from BSG as well as the antioxidant capacity of the extracts.