Spent Brewer Research Articles

Mathematical Modelling of Tensile Mechanical Behavior of a Bio-Composite Based on Polybutylene-Succinate and Brewer Spent Grains.

A model based on the fitting of stress-strain data by tensile tests of bio-composites made of a bioplastic (polybutylene succinate (PBS)) and brewer spent grain filler (BSGF) is developed. Experimental tests were performed for various concentrations of BSGF in the range from 2% to 30%. The model is suitable for describing the elastic-plastic behavior of these materials in terms of two mechanical parameters, tensile stress and tensile stiffness (or Young's modulus), depending on the filler concentration. The mechanical characteristics, derived from the fit parameters, show good agreement with the experimental data. The mathematical model used here could be an important aid for the experimentation and manufacturing process as it allows the prediction of the mechanical tensile parameters of a mixture with different filler concentrations, avoiding the long and complex preparation cycle of bio-composites, as well as the specific mechanical tests. The physical properties required by the objects created with the PBS-BSGF bio-composite by the partners/stakeholders of the research project co-financing this research can be quite different; therefore, a mathematical model that predicts some of the mechanical properties in terms of the mixture composition may be useful to speed up the selection of the required amount of BSGF in the mixture.

Applying Subcritical Water Extraction to Obtain Bioactive Compounds and Cellulose Fibers from Brewer Spent Grains

Of the three types of waste generated in beer processing, brewer’s spent grain (BSG) is the most abundant and has a high potential for valorization. In this work, defatted BSG (DB) was subjected to an extraction process with subcritical water at different temperatures to obtain extracts rich in phenols and the cellulosic fractions, which were also purified by using hydrogen peroxide (H2O2). The results showed that the dry extracts obtained at 170 °C were richer in phenolics (24 mg Gallic Acid Equivalent (GAE) g−1 DB), but with lower antioxidant capacity (71 mg DB·mg−1 2,2-diphenyl-1-pikryl-hydrazyl). This extract also showed the highest antibacterial potential against L. innocua (80 mg·mL−1) and E. coli (140 mg·mL−1) than those obtained at lower temperatures. The purification of cellulose from the treated residues, using hydrogen peroxide, revealed that DB is a limited source of cellulose material since the bleached fractions showed low yields (20–25%) and low cellulose purity (42–71%), even after four bleaching cycles (1 h) at pH 12 and 8% H2O2. Despite this, the subcritical water extraction method highlights the potential of a simple process as a technological option to convert underutilized side streams like beer bagasse into added-value, potential ingredients for innovative food and pharmaceutical applications.

Isolation and Structural Characterization of Natural Deep Eutectic Solvent Lignin from Brewer's Spent Grains.

Brewer's spent grains (BSG) offer valuable opportunities for valorization beyond its conventional use as animal feed. Among its components, lignin-a natural polymer with inherent antioxidant properties-holds significant industrial potential. This work investigates the use of microwave-assisted extraction combined with acidic natural deep eutectic solvents (NaDESs) for efficient lignin recovery, evaluating three different NaDES formulations. The results indicate that choline chloride-lactic acid (ChCl-LA), a NaDES with superior thermal stability as confirmed via thermogravimetric analysis (TGA), is an ideal solvent for lignin extraction at 150 °C and 15 min, achieving a balance of high yield and quality. ChCl-LA also demonstrated good solubility and cell disruption capabilities, while microwaves significantly reduced processing time and severity. Under optimal conditions, i.e., 150 °C, 15 min, in the presence of ChCl-LA NaDES, the extracted lignin achieved a purity of up to 79% and demonstrated an IC50 (inhibitory concentration 50%) of approximately 0.022 mg/L, indicating a relatively strong antioxidant activity. Fourier transform infrared (FTIR) and 2D-HSQC NMR (heteronuclear single quantum coherence nuclear magnetic resonance) spectroscopy confirmed the successful isolation and preservation of its structural integrity. This study highlights the potential of BSG as a valuable lignocellulosic resource and underscores the effectiveness of acidic NaDESs combined with microwave extraction for lignin recovery.

Brewer's Spent Grain-Cellulose-Coated Copper Electrode-Based Extended Gate Field-Effect Transistor for Nonenzymatic Glucose Detection toward Diagnosis of Diabetes Mellitus.

The demand for environmentally friendly, reliable, and cost-effective electrodes for glucose sensor technology has become a major research area in the paradigm shift toward green electronics. In this regard, cellulose has emerged as a promising flexible biopolymer solution with unique properties such as biocompatibility, biodegradability, nontoxicity, renewability, and sustainability. Because of their large surface area and porous structure, fibrous cellulose substrates quickly adsorb and disperse analytes at detection sites. This work focuses on utilizing glyoxal-treated cellulose (derived from brewer's spent grain (BSG)) for the fabrication of extended gate field-effect transistor (EGFET)-based glucose sensors. This investigation extends to the utilization of BSG-cellulose for glucose detection in biomimicking electrolytes (phosphate buffer saline) to facilitate glucose detection in human blood samples. The fabricated electrode demonstrates a linear range of glucose detection from 1 to 13.5 mM with a Langmuir adsorption coefficient (K) of 0.102. Also, its selectivity toward glucose over interfering molecules such as sucrose, fructose, ascorbic acid, and uric acid under physiological conditions has been demonstrated. This cellulose-based EGFET electrode exhibits a sensitivity of 6.5 μA mM-1 cm-2 with a limit of detection (LOD) of 0.135 mM. Computational studies by density functional theory calculations confirmed the higher binding affinity of glucose molecules with glyoxal-modified cellulose (-0.95 eV) than with pristine cellulose (-0.46 eV). Here, the novelty lies in the fabrication of electrodes with biodegradable catalysts and their integration into the EGFET configuration.

Catabolic gene indices of hydrocarbon diminution in Ultisol treated with cropped Bacillus altitudinis-amendments

This study evaluated catabolic gene expression as an index of hydrocarbon breakdown in ultisol treated with Bacillus altitudinis-Cropped Biofertilizers derived from Biosolid and Brewer Spent Grain (BSG) using phenotypic and molecular methods. We observed significant reductions in Total Petroleum Hydrocarbons (TPH) concentrations with both amendments, albeit the biosolid based amendment was markedly more effective. Concurrently, there was a substantial increase in hydrocarbon-degrading bacteria. Notably, the bulk of Operational Taxonomic Units (OTUs) in biosolid (95.77 %) and BSG (93.00 %) amended Ultisol were Proteobacteria, Acidobacteria, Actinobacteria, and Planctomycetes, which are key players in hydrocarbon bioremediation. We observed the presence of eleven hydrocarbon-degrading genes through M5nr analysis. These genes encompass essential catalysts for aliphatic hydrocarbon degradation and hydrocarbon desulfurization. Notably, these enzymes/genes include Bacterial Flavin-bound Monooxygenase (AlmA), Alkane Monooxygenase (AlkM), Alpha Ketoglutarate Dependent Dioxygenase (alkB), Propane Monooxygenase (PrM), Cytochrome P450 (cP450), Methane Monooxygenase/Ammonia Monooxygenase (MMO/AMO) subunits A, B, and C, Alkane Sulfonate Monooxygenase (ssuD), Alkane Sulfonates Transport System Permease Protein (ssuC), Dibenzothiophene Monooxygenase (dszC), Dibenzothiophene-Sulfone Monooxygenase (dszA), and Dibenzothiophene-5,5-Dioxide Monooxygenase (dszB). These genes play pivotal roles in the degradation of aliphatic hydrocarbons and hydrocarbon desulfurization. Interestingly, unique gene expression patterns were observed for each amendment, with Actinomycetales and Bulkhoderiales orders expressing the majority of identified genes. These findings have revealed the amendment-specific microbial and genetic alterations and, the diversity and potential of the annotated genes induced by the Bacillus altitudinis-Cropped Biofertilizers (biosolid and BSG amendments) for effective remediation of hydrocarbon-contaminated soils.

Anti-inflammatory Effect of Brewer's Spent Grain In Vitro

Anti-inflammatory Effect of Brewer's Spent Grain In Vitro

Effects of Alkaline Extraction pH on Amino Acid Compositions, Protein Secondary Structures, Thermal Stability, and Functionalities of Brewer's Spent Grain Proteins.

A high alkaline pH was previously demonstrated to enhance the extraction yield of brewer's spent grains (BSG) proteins. The effects of extraction pH beyond the extraction yield, however, has not been investigated before. The present work examined the effects of extraction pH (pH 8-12) on BSG proteins' (1) amino acid compositions, (2) secondary structures, (3) thermal stability, and (4) functionalities (i.e., water/oil holding capacity, emulsifying, and foaming properties). The ideal extraction temperature (60 °C) and BSG-to-solvent ratio (1:20 w/v) for maximizing the extraction yield were first determined to set the conditions for the pH effect study. The results showed that a higher extraction pH led to more balanced compositions between hydrophilic and hydrophobic amino acids and higher proportions of random coils structures indicating increased protein unfolding. This led to superior emulsifying properties of the extracted proteins with more than twofold improvement between pH 8 and a pH larger than 10. The extraction pH, nevertheless, had minimal impact on the water/oil holding capacity, foaming properties, and thermal denaturation propensity of the proteins. The present work demonstrated that a high alkaline pH at pH 11-12 was indeed ideal for both maximizing the extraction yield (37-46 wt.%) and proteins' functionalities.

A Comparative Study of Composition and Soluble Polysaccharide Content between Brewer's Spent Yeast and Cultured Yeast Cells.

Yeast, crucial in beer production, holds great potential owing to its ability to transform into a valuable by-product resource, known as brewer's spent yeast (BSY), with potentially beneficial physiological effects. This study aimed to compare the composition and soluble polysaccharide content of Brewer's spent yeast with those of cultured yeast strains, namely Saccharomyces cerevisiae (SC) and S. boulardii (SB), to facilitate the utilization of BSY as an alternative source of functional polysaccharides. BSY exhibited significantly higher carbohydrate content and lower crude protein content than SC and SB cells. The residues recovered through autolysis were 53.11%, 43.83%, and 44.99% for BSY, SC, and SB, respectively. Notably, the polysaccharide content of the BSY residue (641.90 μg/mg) was higher than that of SC (553.52 μg/mg) and SB (591.56 μg/mg). The yields of alkali-extracted water-soluble polysaccharides were 33.62%, 40.76%, and 42.97% for BSY, SC, and SB, respectively, with BSY comprising a comparable proportion of water-soluble saccharides made with SC and SB, including 49.31% mannan and 20.18% β-glucan. Furthermore, BSY demonstrated antioxidant activities, including superoxide dismutase (SOD), ABTS, and DPPH scavenging potential, suggesting its ability to mitigate oxidative stress. BSY also exhibited a significantly higher total phenolic compound content, indicating its potential to act as an effective functional food material.

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.

Spent brewer's yeast as a selective biosorbent for metal recovery from polymetallic waste streams.

While the amount of electronic waste is increasing worldwide, the heterogeneity of electronic scrap makes the recycling very complicated. Hydrometallurgical methods are currently applied in e-waste recycling which tend to generate complex polymetallic solutions due to dissolution of all metal components. Although biosorption has previously been described as a viable option for metal recovery and removal from low-concentration or single-metal solutions, information about the application of selective metal biosorption from polymetallic solutions is missing. In this study, an environmentally friendly and selective biosorption approach, based on the pH-dependency of metal sorption processes is presented using spent brewer's yeast to efficiently recover metals like aluminum, copper, zinc and nickel out of polymetallic solutions. Therefore, a design of experiment (DoE) approach was used to identify the effects of pH, metal, and biomass concentration, and optimize the biosorption efficiency for each individual metal. After process optimization with single-metal solutions, biosorption experiments with lyophilized waste yeast biomass were performed with synthetic polymetallic solutions where over 50% of aluminum at pH 3.5, over 40% of copper at pH 5.0 and over 70% of zinc at pH 7.5 could be removed. Moreover, more than 50% of copper at pH 3.5 and over 90% of zinc at pH 7.5 were recovered from a real polymetallic waste stream after leaching of printed-circuit boards. The reusability of yeast biomass was confirmed in five consecutive biosorption steps with little loss in metal recovery abilities. This proves that spent brewer's yeast can be sustainably used to selectively recover metals from polymetallic waste streams different to previously reported studies.

Spent brewer’s yeast encapsulated by spray drying: a promising bioproduct for dairy cow feeding supplementation

Spent brewer’s yeast encapsulated by spray drying: a promising bioproduct for dairy cow feeding supplementation

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.

Using Spent Brewer’s Yeast to Encapsulate and Enhance the Bioavailability of Sonochemically Nanostructured Curcumin

This study is aimed at investigating the possibility of using spent cells of brewer’s yeast Saccharomyces cerevisiae to encapsulate the plant antioxidant curcumin and the effect of such an approach on the bioavailability of BAS in an in vitro digestion model. Spent brewer’s yeast is a significant volume organic waste that is difficult to dispose of, which makes additional options for its use very promising. Encapsulation of curcumin into spent yeast cells was carried out in a nanostructured manner. The encapsulation process was studied using laser dynamic light scattering, inverted and luminescence microscopy, and FTIR analysis. The efficiency and feasibility of curcumin encapsulation process was evaluated by determining the encapsulation efficiency index and modeling the in vitro digestion process. From these studies, it was found that spent yeast cells are capable of acting as a “delivery system” for curcumin. Encapsulation efficiencies of 47.7% can be achieved if curcumin is prenanostructured. Analysis of the potential bioavailability of the plant antioxidant in an in vitro gastric digestion model showed that the technology of encapsulation into yeast cells allows for curcumin retention of 79.5%.

Recycling of yeast multifunctional autolysates and extracts in the food industry

Recycling of industrial waste is one of the most crucial problems for the food industry. The forces of modern researchers are focused on solving this problem and using the biopotential of spent resources. Residual yeast from fermentation industries, in particular brewing, is of particular interest among the variety of food production waste. This is due to the extremely rich chemical composition of the yeast cell, and the possibility of obtaining a wide range of ingredients that exhibit both biological activity and technologically significant properties. Spent brewer's yeast is rich in proteins and carbohydrates, as well as vitamins B and minerals. The protein fraction, which accounts for 45–60% by dry weight (dw), contains all essential amino acids in sufficient quantities, which allows considering this secondary material resource an excellent source of protein with high biological value and a well-balanced AA profile. The carbohydrate fraction, comprising approximately 40% by dw, consists of intracellular carbohydrates (such as simple sugars and glycogen) as well as cell wall polysaccharides (such as β-glucan and α-mannan). Special emphasis is placed on the cell wall components due to their significant multidirectional biological activity and technologically important properties. Thus, β-glucan and α-mannan, along with emulsifying, sorbing and stabilizing properties, exhibit antioxidant and antimicrobial activity, immunomodulatory and prebiotic properties. This review presents an analysis of yeast autolysates and extracts sources as well as the influence of cultivation conditions and production methods on their chemical composition.

Sequential Extraction and Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy Monitoring in the Biorefining of Brewer's Spent Grain.

The brewing industry plays a significant role in producing a substantial annual volume of by-products, which contributes to the global accumulation of food waste. The primary by-product generated is brewer's spent grain (BSG), a lignocellulosic biomass rich in proteins, fiber, and moisture content. Leveraging biorefining and valorization techniques for BSG represents a promising strategy to enhance sustainability, resilience, and circularity within the brewing chain. To date, most studies have focused on extracting proteins from BSG. Yet, it is crucial to note that the fiber part of BSG also holds considerable potential for biorefining processes. This study introduces a novel sequential extraction method designed to integrally recover the major components of BSG. Notably, it introduces a reactive extraction approach that enables the simultaneous extraction and tuneable functionalization of the hemicellulose component. Additionally, the study assesses the utility of the attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy as a user-friendly tool to monitor and evaluate the effectiveness of the fractionation process. This spectroscopic technique can provide valuable insights into the changes and composition of BSG throughout the extraction process.

Nutritional Potential of Spent Brewer's Yeast, A Residual By-Product of Beer Production in Breweries for Future Applications

The recovery of by-products from food processing chains represents an area of interest in the current world. Waste from beer production, such as beer lees or spent brewer's yeast, constitutes between 1.5 and 3 kg/100 L of beer, representing a source of pollution but a by-product available in quantity. This study aims to characterize the beer lees from breweries and propose possible ways of recovery. The scientific methods have been applied to highlight the nutritional potential of this by-product. Spent brewer's yeast is a high-biological value protein source (46.77%) with a well-balanced amino acid profile. Amino acids (glutamic acid and aspartic acid) and the essential amino acids leucine, lysine and valine are the most abundant, while sulfur amino acids, such as methionine and cysteine, are the least abundant. With a high mineral content (7.3%), the spent brewer's yeast contains significant amounts of manganese 5.54x10-2 mg/k, sodium 3.92x10-2 mg/k, and potassium 3.59x10-2 mg /k. The B complex vitamins are present in large quantities, followed by vitamins C, A and D. Less than 3% of the composition of the spent brewer's yeast is made up of lipids. The most abundant of fatty acids determined for the saturated category is palmitic acid, while oleic acid represents monounsaturated fatty acids, and polyunsaturated fatty acids are represented by linoleic acid and linolenic acid. Carbohydrates (32.77 %) are also important constituents of the dry matter of this by-product. This study showed that spent beer yeast is a source of polyphenol. Spent brewer's yeast has advantages for being incorporated into animal nutrition to meet nutritional needs. Further studies could lead to the production of activated carbon and hydrogen as excellent sources of alternative energy.

Versatile Applications of Brewer's Spent Grain: Solid-State Fermentation and Nutritional Added Value.

Brewer's spent grain (BSG) is a major by-product in the beer-brewing process which contributes to 85% of the entire generated by-product in the brewing process. BSG is rich in proteins, and most of the malt proteins (74-78%) remain insoluble in BSG after the mashing process. Solid-state fermentation (SSF) is a promising bioprocess that enables microorganisms to survive in environments with minimal water and has shown to enhance the nutritional composition of BSG. In this review, the potential application of protein, amino acids (proline, threonine, and serine), phenolic contents, and soluble sugars (glucose, fructose, xylose, arabinose, and cellobiose) extracted from BSG by various microorganisms using SSF is explored. Incorporation of BSG into animal feed, human diets, and as a substrate for microorganisms are the prospects that could be implemented in the industrial scale. This review also discussed various advances to improve the fermentation yield such as symbiotic fermentation, the addition of nitrogen supplements, and an optimal mixture of the agro-industrial waste substrate. Future perspectives on SSF are also addressed to provide important ideas for immediate and future studies. However, challenges include optimizing SSF conditions and design of bioreactors, and operational costs must be addressed in the future to overcome current obstacles. Overall, this mini review highlights the potential benefits of BSG utilization and SSF in a sustainable way.

Purification of bioactive peptides from spent yeast autolysates

Spent brewer’s yeast have been described as an important source for bioactive peptides, with their properties well proven over the years. Besides the brewing sector, growing of large-scale processes on synthetic biology industry has generated a substantial amount of spent engineered yeast with further potential to be valued in a circular economy approach. In line with this perception, in this work, peptide-rich fractions were obtained from spent yeast peptide-rich extract autolysate (“ESY1”), using two different techniques, namely protein ultrafiltration and size-exclusion chromatography (SEC). Both methods allowed the production of different peptide fractions with diverse protein content, molecular weight distribution and peptides sequences. Overall, fractions with higher protein content and more purified reveal higher bioactivities, namely antihypertensive and anticholesterolemic, emphasizing that the purification process is an important step to include in production process of a dietary supplement with these specific features. In addition, significant antioxidant capacity values for peptide fractions purified by SEC were obtained, highlighting their potential use in economic sectors where antioxidant capacity has a massive impact, such as cosmetics.

Influence of Hydrothermal Treatment of Brewer's Spent Grain on the Concentration and Molecular Weight Distribution of 1,3-1,4-β-D-Glucan and Arabinoxylan.

Brewer's spent grain (BSG) is the most abundant residual in the brewing process. Non-starch polysaccharides such as 1,3-1,4-β-D-glucan (β-glucan) and arabinoxylan (AX) with proven beneficial effects on human health remain in this by-product in high amounts. Incorporating the valuable dietary fiber into the food industry could contribute to a healthy diet. However, a major challenge is extracting these dietary fibers (i.e., β-glucan and AX) from the solid residue. In this study, hydrothermal treatment (HT) was applied to dissolve the remaining water-insoluble carbohydrates from BSG with the aim to extract high amounts of β-glucan and AX. Particular focus was placed on the molecular weight (MW) range above 50 kDa and 20 kDa, respectively, as these are considered to have health-promoting effects. Different treatment temperatures, reaction times, and internal reactor pressures were tested to determine the best process settings to achieve high yields of β-glucan and AX and to examine the influence on their molecular weight distribution (MWD). Overall, 85.1% β-glucan and 77.3% AX were extracted corresponding to 6.3 g per kg BSG at 160 °C and 178.3 g kg-1 at 170 °C, respectively. However, less than 20% of both fiber substances were in the desirable MW range above 50 kDa and 20 kDa, respectively. When lower temperatures of 140 and 150 °C were applied, yields of only 3.0 g kg-1 β-glucan and 128.8 g kg-1 AX were obtained, whereby the proportion of desirable fiber fractions increased up to 45%. Further investigations focused on the heat-induced degradation of monosaccharides and the formation of undesirable by-products (i.e., HMF and furfural) that might pose a health risk.

Effects of Iron, Lime, and Porous Ceramic Powder Additives on Methane Production from Brewer's Spent Grain in the Anaerobic Digestion Process.

The process of anaerobic digestion used for methane production can be enhanced by dosing various additive materials. The effects of these materials are dependent on various factors, including the processed substrate, process conditions, and the type and amount of the additive material. As part of the study, three different materials-iron powder, lime, and milled porous ceramic-were added to the 30-day anaerobic digestion of the brewer's spent grain to improve its performance. Different doses ranging from 0.2 to 2.3 gTS × L-1 were tested, and methane production kinetics were determined using the first-order model. The results showed that the methane yield ranged from 281.4 ± 8.0 to 326.1 ± 9.3 mL × gVS-1, while substrate biodegradation ranged from 56.0 ± 1.6 to 68.1 ± 0.7%. The addition of lime reduced the methane yield at almost all doses by -6.7% to -3.3%, while the addition of iron powder increased the methane yield from 0.8% to 9.8%. The addition of ceramic powder resulted in a methane yield change ranging from -2.6% to 4.6%. These findings suggest that the use of additive materials should be approached with caution, as even slight changes in the amount used can impact methane production.