Brewery Spent Grain Research Articles

Enhancing the biorefinery of brewery spent grain by deep eutectic solvent pretreatment: Optimisation of polysaccharide enrichment through a response surface methodology

One of the main challenges in biorefinery is the efficient fractionation and use of lignocellulosic biomass. In this sense, pretreatment with deep eutectic solvents (DES) is highlighted as a clean and effective separation method, due to its selective solubilisation of hemicellulose and lignin fractions while preserving cellulose. This study presents a process of the enrichment of polysaccharide content and the improvement of enzymatic digestibility using choline chloride (ChCl) and lactic acid (LA) or glycerol (Gly) in brewery spent grain (BSG) pretreatment. Additionally, it describes how improvements can be made in obtaining polysaccharide-rich material through a response surface methodology, this by means of analysing the operational conditions (temperature, reaction time, and molar ratio) using ChCl:LA. The optimised operational conditions (130 °C, 90 min, and 1:8 mol/mol) generate a 75 % enrichment of polysaccharide fraction and the remotion of 77.13 %, 50.70 %, and 100 % of acid-soluble lignin, xylan, and arabinan, respectively. Moreover, the process enhances the saccharification of glucan and xylan to almost 70 % using Cellic CTec2, and to 80 % of glucan and 40 % of xylan using A. niger CECT 2700 enzymatic extract. This constitutes a promising approach to the fractioning of cellulose and lignin from BSG through DES pretreatment, which is unfeasible using traditional pretreatment methods.

Anaerobic co‑digestion of bovine ruminal waste and brewery spent grain: Effects of inoculum to substrate ratio, mixing ratio, process stability, organic matter removal, and methane yield

The technological potential of co-digesting bovine rumen waste (BRW) with brewery spent grain (BSG) is significant, offering enhanced biogas production and effective waste management. This study's findings demonstrate that the anaerobic digestion process becomes significantly more efficient when difficult to degrade BRW is combined with easily degradable BSG. The highest methane yield obtained in the mono-digestion of BRW was 127.11 NmLCH4 gVS−1 with biodegradability of 33.89 % in inoculum to substrate ratio (ISR) 2, and for de BSG obtained was 304.18 NmLCH4 gVS−1 with biodegradability of 68.26 % in ISR 4. The overall average obtained in co-digestion for volatile solids (VS) removal was 26.28 %, and the concentration of methane present in the biogas was 57.18 %. The VS removal efficiency and the increase in biogas and methane yield were directly proportional to the rise in ISR and the proportion of BSG in the mixture. Specifically, the ideal mix of 25 % BRW with 75 % BSG at ISR 4 resulted in a notable methane yield of 255.30 NmLCH4 gVS−1. This process stabilizes digestion and significantly improves solids removal and methane concentration, making it a highly efficient solution for sustainable energy production and industrial waste management.

Harnessing Brewery Spent Grain for Polyhydroxyalkanoate Production

The utility of brewery spent grain (BSG), a byproduct of the beer production process, for the synthesis of polyhydroxyalkanoates (PHAs), is a significant advancement towards sustainable and cost−effective biopolymer production. This paper reviews the upcycling potential of BSG as a substrate for PHA production, utilizing various biotechnological approaches to convert this abundant waste material into high−value biodegradable polymers. Through a comprehensive review of recent studies, we highlight the biochemical composition of BSG and its suitability for microbial fermentation processes. This research delves into different methodologies for PHA production from BSG, including the use of mixed microbial cultures (MMCs) for the synthesis of volatile fatty acids (VFAs), a critical precursor in PHA production, and solid−state fermentation (SSF) techniques. We also examine the optimization of process parameters such as pH, temperature, and microbial concentration through the application of the Doehlert design, revealing the intricate relationships between these factors and their impact on VFA profiles and PHA yields. Additionally, this paper discusses challenges and future perspectives for enhancing the efficiency and economic viability of PHA production from BSG. By harnessing the untapped potential of BSG, this research contributes to the development of a circular economy model, emphasizing waste valorization and the creation of sustainable alternatives to conventional plastics.

Extraction and Characterization of Cellulose from Coffee Husk and Brewery’s Spent Grain Fibers Using Alkali-Hydrogen Peroxide Treatment Method

Coffee husk (CH) and brewery spent grain (BSG) fibers are sustainable industrial residues that consist of cellulose. The present study aimed at the extraction of cellulose from CH and BSG fibers and to study the effect of alkali-hydrogen peroxide (5% NaOH–7% H2O2) treatment during the extraction by characterizing the extracted cellulose. Characterization of cellulose particles, such as crystallinity, functional groups, thermal properties, and morphology, was conducted by performing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyzer (TGA), and scanning electron microscopy (SEM), respectively. The finding shows that the maximum cellulose yields obtained from CH and BSG fibers are 37.3% and 26.5%, respectively. From the XRD results, the cellulose obtained from CH fiber (C-CH) and from BSG fiber (C-BSG) showed diffractive peaks with the highest intensity of approximately 1,003 and 1,236 counted at 2θ = 22°, respectively. A reduction in the absorption of peaks was observed on the FTIR spectrum for both C-BSG and C-CH samples at different wavelengths. SEM demonstrated that the surface roughness of the celluloses was enhanced. TGA showed that the maximum temperature decomposition observed for both C-CH and C-BSG is 360°C and 380°C, respectively. Generally, in this study, alkali-hydrogen peroxide (5% NaOH–7% H2O2) treatment was effectively used for the treatment of BSG and CH fibers for the extraction and surface modification of cellulose particles. The extracted cellulose in the present study can be used as an alternative to conventional cellulose for the manufacturing of biocomposite materials, preparation of particle boards and furniture, and production of food packaging materials.

Engineering of brewery waste-derived graphene quantum dots with ZnO nanoparticles for treating multi-drug resistant bacterial infections

In this study, the antibacterial efficiency of graphene quantum dots (GQDs) derived from brewery spent grain (BSG) in combination with zinc oxide (ZnO) nanoparticles against the methicillin-resistant Staphylococcus aureus (MRSA) isolated from clinical wound specimens is investigated for the first time. The crystallinity, morphology, and structural defects of the nanomaterials were analysed in detail by the X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and Raman spectroscopy techniques. The layered morphology of BSG-derived reduced graphene oxide (BrGO), d-spacing, and the average particle size of GQDs were further examined by a high-resolution transmission electron microscopy (HR-TEM). Compared to individual GQDs and ZnO, ZnO/GQDs composites showed a better antibacterial activity against Escherichia coli, and Staphylococcus aureus. ZnO/GQDs also demonstrated significant efficiency in disinfecting the MRSA (ATCC and clinical isolates from wound specimens). Density functional theory (DFT) calculations confirmed the substantial clustering of functional groups at the edges of nanomaterial. The disinfection mechanism of MRSA is elucidated for the first time with DFT calculations. Cytotoxicity experiments with the 3T3 mouse embryo fibroblasts testified that ZnO/GQDs are not toxic to mammalian cells.

Sustainable Co-Production of Xylanase, Cellulase, and Pectinase through Agroindustrial Residue Valorization Using Solid-State Fermentation: A Techno-Economic Assessment

This work describes the evaluation of the solid-state fermentation (SSF) bioprocess utilizing brewery spent grain (BSG) and apple pomace (AP) as carbon sources and matrices for microorganism growth to produce xylanase, pectinase, and cellulase. The process was assessed at a larger scale by designing a packed column-type bioreactor equipped with sensors for monitoring critical parameters such as CO2 concentration, humidity, and temperature. Then, process simulation was used to evaluate the techno-economic feasibility of the bioprocess at an industrial scale. The analysis centered on evaluating which formulation, primarily containing xylanase (scenario 1), pectinase (scenario 2), or cellulase (scenario 3), yielded the most promising results for advancing to the commercial stage. Additionally, a sensitivity analysis was conducted to explore the influence of variations in raw material costs and enzyme prices. The obtained results at a higher scale were within the expected results obtained under optimum conditions. Scenario 1 exhibited strong economic viability with further optimization potential (base case: 5000 kg/batch with an ROI of 37.59%, payback time of 2.66 years, IRR of 26.8%, and net present value of USD 7,325,537). The sensitivity analysis revealed that changes in enzyme prices, particularly xylanase, could significantly influence the process’s profitability. This study also demonstrated the potential for cost optimization by selecting a more cost-effective inoculum media and optimizing water usage to enhance process efficiency and sustainability.

Production of Composite Briquette Fuel from Brewery Wastewater Sludge and Spent Grains.

Biomass waste energy recovery is a significant method for recycling energy from waste and capturing it for use in renewable energy sources. The abundance of brewing byproducts, such as brewery spent grain (BSG) and brewery wastewater sludge (BWWS), as well as their high carbon concentrations gives these wastes energy potential. With 20% molasses utilized as a binding agent to maximize the high caloric value of the briquette, this study sought to examine the quality of mixed briquettes made from BSG and BWWS. In order to make composite briquettes with a maximum caloric content of 19.94 MJ/kg, the ideal conditions were chosen, which included a temperature of 350°C, a production period of 60 min, and a 75% BSG mixing ratio. It can be compared to sawdust briquettes, which have a calorific value of 22.88 MJ/kg, by looking at the calorific value of densified with pressure 100 bar for mixed carbonized briquettes vs mixed noncarbonized briquettes (21.13 MJ/kg). The value of R 2 was 0.9607 and indicated that 96.07% of the total validation in the calorific value correlation between experimental and predicted values. The finding of the study showed that the efficiency of the quadratic model in fitting the data would be higher under the conditions of the experiment. Based on ISO 17225-6 fuel quality classes and specifications for graded nonwoody pellets, the study concluded that using BSG and BWWS as alternative energy sources meets those requirements.

Evaluation of Proximate Composition, Physicochemical Properties, and Sensory Attributes of Instant Flour from Brewery Spent Grain, by Blending with Maize (Zea mays L.) and Germinated Chickpea (Cicer arietinum L.).

Brewer's spent grain (BSG) is a nutritional-rich by-product of the brewing industry used in different food product development processes. "Corn Soya Blend" (CSB) is prepared from heat-treated maize and soybeans according to the specifications set by the World Food Program (WFP). Three instant formulations-IF20 (70% maize, 10% chickpea, and 20% BSG), IF15 (70% maize, 15% chickpea, and 15% BSG), and IF10 (70% maize, 20% chickpea, and 10% BSG)-were developed in this research. Proximate composition, functional properties, and antinutritional factors were analysed. The sensory quality of porridge samples developed from the instant flour was evaluated using a consumer-oriented panel (food science and technology students) at a five-point hedonic scale. Accordingly, moisture, crude fibre, crude protein, total ash, and crude fat contents increased significantly (p < 0.05) as a result of BSG ratio inclusion. Bulk density decreased significantly (p < 0.05) while the BSG proportion increased but water absorption capacity increased when the proportion of BSG increased. Phytate and tannin contents were also increased while the BSG proportion increased. However, an increase in germinated chickpea proportion significantly (p < 0.05) decreased phytate and tannin contents. While BSG increased, the overall acceptability of porridge samples decreased, with the exception of mouthfeel. According to this study, up to 15% of BSG, 70% maize, and 15% chickpea could be used for instant flour preparation which has a comparable sensory characteristic with the commercial CSB. Hence, it can be used as a substitute for corn-soya mix.

Biorefinery of brewery spent grain to obtain bioproducts with high value-added in the market

The brewery industry is under economic and environmental pressure to minimize residual management costs, particularly brewery spent grain (BSG), which accounts for 80–85% (w/w) of the total by-products generated. BSG is a lignocellulosic material primarily composed of carbohydrates, proteins and lipids. Developing a biorefinery model for conversion of BSG into value-added products is a plausible idea. Previous work optimized the pretreatment of BSG with the ionic liquid [N1112OH][Gly] and further release of fermentable sugar-containing solutions by enzymatic hydrolysis, using an enzymatic cocktail obtained by solid-state fermentation of BSG with Aspergillus brasiliensis CECT 2700 and Trichoderma reesei CECT 2414. The current work ends the biorefinery process, studying the fermentation of these culture media with two LAB strains, Lactobacillus pentosus CECT 4023 and Lactobacillus plantarum CECT 221, from which the production of organic acids, bacteriocins, and microbial biosurfactants (mBS) was obtained. In addition to the bacteriocin activity observed, a mass balance of the whole biorefinery process quantified the production of 106.4 g lactic acid and 6.76 g mBS with L. plantarum and 116.1 g lactic acid and 4.65 g mBS with L. pentosus from 1 kg of dry BSG. Thus, BSG shows a great potential for waste valorization, playing a major role in the implementation of biomass biorefineries in circular bioeconomy.

Bio-refinery of brewery spent grain utilizing natural deep eutectic solvent-induced subcritical water

This research aimed to valorize brewery spent grain (BSG) using subcritical water hydrolysis (SWH) modified by six different natural deep eutectic solvents (DES) and determining their bipotentialities. DES-induced SWH BSG hydrolysates showed the highest sugar content 46.63 ± 2.10 mg glucose, protein 228.08 ± 5.52 mg BSA, total flavonoids 22.87 ± 0.23 mg RE, phenolic compounds 8.00 ± 0.25 mg GAE from per gram dried BSG. A total of 9 different essential amino acids were identified from the BSG-hydrolysates; among them, leucine, isoleucine, phenylalanine, and histidine were the most prominent. The major phenolic compounds in the hydrolysates are gallic acid, protocatechuic acid, catechin, 4-hydroxybenzoic acid, naringin, and ferulic acid. BSG hydrolysates demonstrated antimicrobial activities and FT-IR analysis confirmed the presence of bioactive compounds. This comprehensive profiling of different bioactive compounds from BSG using DES-mediated SWH can be helpful for the efficient valorization of BSG for industrial purposes.

Agroindustrial and food processing residues valorization for solid-state fermentation processes: A case for optimizing the co-production of hydrolytic enzymes

In the pursuit of sustainability, managing agro-industrial and food processing residues (AFR) efficiently is crucial. This study proposes a systematic approach to convert AFR into valuable products via solid-state fermentation (SSF). Using fungal enzyme production as a case study, this adaptable methodology suits any SSF bioprocess. Initially, AFR's physicochemical properties were evaluated to assess their feasible use as carbon sources and solid matrices for SSF. Then, five strains were screened for their capability to produce enzymes (Xylanase, X; pectinase, P; cellulase, C). Apple pomace (AP) and brewery spent grain (BSG) with Aspergillus sp. (strain G5) were selected. Subsequent steps involved a two-phase statistical approach, identifying critical factors and optimizing them. Process conditions were screened using a Plackett-Burman design, narrowing critical variables to three (BSG/AP, pH, humidity). Response Surface Methodology (Central Composite Design) further optimized these factors for co-synthesis of X, P, and C. The humidity had the most significant effect on the three responses. The optimum conditions depended on each enzyme and were further validated to maximize either X, P or C. The obtained extracts were used for pectin extraction from orange peels. The extract containing primarily xylanase (X = 582.39, P = 22.86, C = 26.10 U mL−1) showed major pectin yield recovery (12.33 ± 0.53%) and it was obtained using the optimal settings of BSG/AP (81/19), humidity (50.40%), and pH (4.58). The findings will enable adjusting process conditions to obtain enzymatic cocktails with a tailored composition for specific applications.

Bacterial community dynamics and associated genes in hydrocarbon contaminated soil during bioremediation using brewery spent grain.

Brewery spent grain (BSG) has previously been exploited in bioremediation. However, detailed knowledge of the associated bacterial community dynamics and changes in relevant metabolites and genes over time is limited. This study investigated the bioremediation of diesel contaminated soil amended with BSG. We observed complete degradation of three total petroleum hydrocarbon (TPH C10-C28) fractions in amended treatments as compared to one fraction in the unamended, natural attenuation treatments. The biodegradation rate constant (k) was higher in amended treatments (0.1021k) than in unamended (0.059k), and bacterial colony forming units increased significantly in amended treatments. The degradation compounds observed fitted into the elucidated diesel degradation pathways and quantitative PCR results showed that the gene copy numbers of all three associated degradation genes, alkB, catA and xylE, were significantly higher in amended treatments. High-throughput sequencing of 16S rRNA gene amplicons showed that amendment with BSG enriched autochthonous hydrocarbon degraders. Also, community shifts of the genera Acinetobacter and Pseudomonas correlated with the abundance of catabolic genes and degradation compounds observed. This study showed that these two genera are present in BSG and thus may be associated with the enhanced biodegradation observed in amended treatments. The results suggest that the combined evaluation of TPH, microbiological, metabolite and genetic analysis provides a useful holistic approach to assessing bioremediation.

Effects of brewer's spent yeast inclusion level and ensiling duration on fermentative, fungal load dynamics, and nutritional characteristics of brewer's spent yeast-based silage

ObjectiveThis study was conducted to evaluate the effect of brewer's spent yeast (BSY) inclusion level and ensiling duration (ED) on fermentative, fungal load dynamics, and nutritional characteristics of brewer's spent-yeast based silage. Materials and methodsTo prepare the silages materials, 4 BSY inclusion levels (0, 10, 20, and 30%) to replace BSG and 3 ED (2,4 and 6 weeks) were arranged in 4 × 3 factorial combination using a completely randomized design (CRD) in 5 replications. The ratio of brewery spent grain (BSG) to wheat bran (WB) used majorly as protein and energy sources, respectively was 30:69 with a 1% salt addition. Parameters measured include observation for surface spoilage, yeast and mold colony count, silage temperature, pH, total dry matter loss (TDML), major proximate, detergent fractions and permanganate lignin, in-vitro organic matter digestibility (IVOMD) and estimated metabolizable energy (EME) values. ResultsThe study revealed that at any BSY inclusion level and ED, extensive mold growths and discolorations were not observed. However, slightly higher values of 6.5, 5.7, and 12.2 colonies forming unit (CFU)/g DM yeast, mold, and total fungal counts (TFC), respectively were recorded only at the 6 weeks of the fermentation period with 30% BSY inclusion level. Brewer's spent yeast inclusion level and ED had a significant (P < 0.05) effect on silage temperature (mean = 18.05 °C) and pH (mean = 4.16). Among proximate and detergent values, crude protein (mean CP g/kg DM = 204.5), neutral detergent fiber (mean NDF g/kg DM = 552.9), and acid detergent fiber (mean ADF g/kg DM = 115.9) responded significantly (P < 0.05) to both BSY inclusion levels and ED. ConclusionAmong nutritional quality, CP, IVOMD, and EME of silage samples were subjected to substantial improvements when silage masses were prepared from 20% BSY inclusion levels and when the same silage materials were allowed to ferment for four weeks. In addition, the lab-based experiment should be supported with additional silage quality parameters like volatile fatty acid content of the silage materials and supplementation of ruminant livestock under both on-station and on-farm conditions using either a pilot and/or target animals.

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.

Effects of Brewery Spent Grain (BSG) included poultry diet on growth performance and meat quality of New Hampshire chicken

An experiment was conducted to evaluate the inclusion effects of Dried Brewery Spent Grain (DBSG) to know its effect on growth performance and meat quality on poultry. Completely randomized design was used to compare the treatments in five replications. The treatments used were 15% DBSG (T1), 20% DBSG (T2), 25% DBSG (T3), Commercial feed (T4) and (0% DBSG) scavenging bird was used as a control. Each treatment contained 10 birds including 200 chickens in the whole investigation. The major factors body weight, carcasses and organs weight, cholesterol, total protein, albumin, and calcium were evaluated. Results showed that mean body weight of the experimental bird after 60 days was not significantly different (p&gt;0.05) among the dietary treatments, i.e., T1 (781.46 g), T2 (738.36 g), T3 (728.91 g) and T4 (753.38 g). Carcass, breast muscle, thigh, wing, shank, liver and spleen were not significantly different (p&gt;0.05) in weight between DBSG included diet and commercial feed. However, dressing percentage (59.3%) of T4 and gizzard (43.20 gm.) in T3 was significantly higher than other treatments. The significantly higher (p&lt;0.05) amount of cholesterol found in T4 (312.01 mg/dl) followed by control diet (239.46 mg/dl), both of which were above than reference range (129-297 mg/dl). However, in other treatments i.e., T1, T2 and T3, the cholesterol content was in between the reference range. Similarly, same level (p&gt;0.05) of total protein, albumin and calcium content in blood serum observed in BSG included diet and commercial diet. Hence, 15% to 20% inclusion of BSG could be the optimum level in diets of New Hampshire chickens.

Effects of Brewery Spent Grain Ash on Lime-Stabilized Clayey Soil

Effects of Brewery Spent Grain Ash on Lime-Stabilized Clayey Soil

Dairy farmer’s perception on feeding, conservation, and constraints of brewery by-products utilization in selected districts of Ethiopia

A survey was conducted in Ada’a, Sululta, and Debre Birhan districts. The districts are located in the vicinity of brewery factories. A semi-structured questionnaire was used to collect data from purposively selected dairy farmers (160). Data were analyzed with a statistical package for social sciences (Version 21). The majority of farmers (69.4%) used wet brewery-spent grain (WBSG), whereas 30% of them used both WBSG and wet brewery spent yeast (WBSY). Farmers obtained WBSG and WBSY only in fresh form from the distributors. The majority of farmers (66.67%) blended WBSG and WBSY with concentrate and roughage feed before feeding it to their animals, while 14.47% fed the by-products alone to their animals. Several farmers (60.1%) responded that the key reason for providing WBSG and WBSY to their livestock was higher production (increased milk and growth rates). The majority (82.78%) of farmers used common salt to extend the shelf life of WBSG and WBSY. Out of 128 (80%) farmers who reported spoilage in WBSG, 49 (38.28%) farmers observed sever mold development, while the remaining 12 (9.38%) and 28 (21.88%) saw change in colour and unpleasant odor. According to 68 (53.13%) of the farmers who experienced in WBSG spoiling, the amount of spoilt was less than 9% and 10–20% of the total purchased. The majority of farmers (87.8%) reported that storage time and storage conditions (temperature, moisture, and humidity) were the primary reasons of WBSG spoilage, whereas 12.2% of the farmers reported that inadequate sanitation of feeding troughs, transportation, and storage facilities were the primary causes of spoilage. The key restrictions of brewery by-product utilization were found as scarcity and high purchasing costs. Farmers (44.38% and 41.86%) believed that feeding WBSG and WBSY to dairy cattle have negative health effect, respectively. In conclusion, insufficient and irregular supply, rising cost of material and transport, spoilage, and health-related hazards are the main constraints of WBSG and WBSY usage. It is suggested that there is a dire need for consistent supply, staying away from the brokers, and preserving the brewery by-products through sun drying, and ensiling. Additionally, more research is required to determine the negative health impact of feeding brewer by-products for dairy cattle.

Health Benefits of High Protein and Dietary Fiber Dry-Fractioned Brewery Spent Grain Fines

Health Benefits of High Protein and Dietary Fiber Dry-Fractioned Brewery Spent Grain Fines

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.

Effect of metals on the regulation of acidogenic metabolism enhancing biohydrogen and carboxylic acids production from brewery spent grains: Microbial dynamics and biochemical analysis.

The present study reports the mixed culture acidogenic production of biohydrogen and carboxylic acids (CA) from brewery spent grains (BSG) in the presence of high concentrations of cobalt, iron, nickel, and zinc. The metals enhanced biohydrogen output by 2.39 times along with CA biosynthesis by 1.73 times. Cobalt and iron promoted the acetate and butyrate pathways, leading to the accumulation of 5.14 gCOD/L of acetic and 11.36 gCOD/L of butyric acid. The production of solvents (ethanol + butanol) was higher with zinc (4.68 gCOD/L) and cobalt (4.45 gCOD/L). A combination of all four metals further enhanced CA accumulation to 42.98 gCOD/L, thus surpassing the benefits accrued from supplementation with individual metals. Additionally, 0.36 and 0.31 mol green ammonium were obtained from protein‐rich brewery spent grain upon supplementation with iron and cobalt, respectively. Metagenomic analysis revealed the high relative abundance of Firmicutes (>90%), of which 85.02% were Clostridium, in mixed metal‐containing reactors. Finally, a significant correlation of dehydrogenase activity with CA and biohydrogen evolution was observed upon metal addition.