Microbial alchemy: upcycling of brewery spent grains into high-value products through fermentation.

Spent grains are one of the lignocellulosic biomasses available in abundance, discarded by breweries as waste. The brewing process generates around 25-30% of waste in different forms and spent grains alone account for 80-85% of that waste, resulting in a significant global waste volume. Despite containing essential nutrients, i.e., carbohydrates, fibers, proteins, fatty acids, lipids, minerals, and vitamins, efficient and economically viable valorization of these grains is lacking. Microbial fermentation enables the valorization of spent grain biomass into numerous commercially valuable products used in energy, food, healthcare, and biomaterials. However, the process still needs more investigation to overcome challenges, such as transportation, cost-effective pretreatment, and fermentation strategy. to lower the product cost and to achieve market feasibility and customer affordability. This review summarizes the potential of spent grains valorization via microbial fermentation and associated challenges.

In vitro strategies to understand the impact of oral intake on the bioavailability and bioactivity of peptides from brewing by-products.

Bioactive peptides from brewer's spent grain (BSG) and brewer's spent yeast (BSY), two by-products of the brewing industry, have great potential as functional food ingredients, dietary supplements or nutraceuticals to reduce the risk of numerous pathological conditions. Nevertheless, the oral administration of these peptides poses great challenges since peptides must undergo gastrointestinal digestion, intestinal absorption and hepatic metabolism, which can affect their bioavailability and, therefore, the expected outcomes. This review provides a comprehensive and critical analysis of the potential impact of the oral route on the bioactivity of BSG/BSY peptides as assessed by in vitro assays and identifies research gaps that require novel approaches/methodologies. The data collected indicate that in addition to the significant influence of gastrointestinal digestion, intestinal absorption and hepatic metabolism also have a major impact on the bioactivity of brewing peptides. The major gap identified was the insufficient evidence regarding hepatic metabolism, which points for the need of employing in vitro assays in this research field to provide such clarification. Thus, to reach the market, the impact of the oral route on the bioactivities of BSG/BSY peptides must be properly studied in vitro to allow adequate/effective administration (dosage/frequency) with a beneficial impact on the population health.

Benzaldehyde acts as a behaviorally active component in brewer's yeast protein powder which attracts B. dorsalis through olfaction.

The Oriental fruit fly, Bactrocera dorsalis, is a significant pest that damages a variety of fruit crops. The effectiveness of chemical pesticides against such pests is limited, raising concerns about pesticide residues and resistance. Proteins naturally attract B. dorsalis and have led to the development of a management strategy known as protein bait attractant technology (BAT). Although the attraction of protein sources to B. dorsalis is well-documented, the biologically active components within these sources are not fully understood. This study employed analytical chemistry, behavioral tests, and electrophysiological techniques to investigate the behaviorally active components of beer yeast protein powder (BYPD), aiming to provide a basis for improving and developing protein baits. An olfactory trap assay confirmed the attractiveness of BYPD, and five components with high abundance were identified from its headspace volatiles using GC-MS. These components included ethanol, isoamyl alcohol, ethyl decanoate, benzaldehyde, and phenylethyl alcohol. Mixtures of these five components demonstrated significant attraction to B. dorsalis adults, with benzaldehyde identified as a potential key component. The attractiveness of benzaldehyde required a relatively large dose, and it was most attractive to adults that had been starved from dusk until the following morning. Attraction of adult flies to benzaldehyde appeared mainly mediated by inputs from olfactory receptors. While EAG data supports that ionotropic receptors could influence the detection of benzaldehyde in female adults, they did not affect female behavior towards benzaldehyde. These findings indicate that benzaldehyde is an important behaviorally active component in BYPD and offer insights for developing novel protein lures to control B. dorsalis in an environmentally friendly manner.

Hydrothermal co-liquefaction of microalgae, sugarcane bagasse, brewer's spent grain, and sludge from a paper recycling mill: Modeling and evaluation of biocrude and biochar yield.

Biomass can be used as an energy source to thermochemical conversion processes to biocrude production. However, the supply and dependence on only one biomass for biocrude production can be an obstacle due to its seasonality, availability, and logistics costs. In this way, biomass waste and agroindustrial residues can be mixture and used as feedstock to the hydrothermal co-liquefaction (co-HTL) process as an alternative to obtaining biocrude. In this sense, the present paper analyzed the biocrude yield influence of the co-HTL from a quaternary unprecedented blend of different biomasses, such as sugarcane bagasse, brewer's spent grain (BSG), sludge from a paper recycling mill (PRM), and microalgae (Chlorella vulgaris). In this way, a simplex lattice design was employed and co-HTL experiments were carried out in a 2000 mL high-pressure stirred autoclave reactor under 275 °C for 60 min, considering 15% of feedstock/water ratio. Significant effects in each feedstock and their blends were analyzed aiming to increase biocrude and biochar yield. It was found that the addition of microalgae is only significant when considered more than 50% into the blend with BSG and PRM sludge to increase biocrude yield.

Effects of brewery by-products based silage on productive performance of crossbred dairy cows.

The present study aimed to evaluate the effect of an increasing levels of brewery by-products based silage on productive performances of 3/4 Friesian x Boran mid-lactating cows. Experimental cows had similar in initial milk yield (11.7 ± 1.0), average days in milk (81.7 ± 6.1) and live weight (LW, 430.7 ± 40.3 kg) but different in parities (2-5).The dietary treatments were arranged randomly in 4 × 4 Latin Square Design that included ad libitum natural pasture hay feeding for all treatments as a roughage source plus a commercial dairy concentrate mix supplemented at 0.5 kg DM (dry matter)/liter of milk produced/day for cows in the control group (T1) and 0.3, 0.5 and 0.7 kg DM of brewery by-products based silage per liter of milk yield/cow/day for cows in T2, T3 and T4 groups, respectively. The study revealed that the daily milk yield of experimental cows was influenced by dietary treatments with relatively higher daily milk yield being recorded (P < 0.05) for cows in the T4 (13.9 l) followed by T3 (13.8 l). Milk composition of cows remained unchanged (P > 0.05) except for fat percentage of the milk that showed a declining trend (P < 0.05) with incremental inclusion levels of brewery by-products based silages. The highest net income (NI, 437.9 Eth. Birr) and marginal rate of return (MRR, 800.7%) was obtained for cows receiving brewery by-products based silage at the rate of 0.7 kg/liter of milk yield as compared to cows in the other treatment groups. Further study is required on the long term effect of brewery by-products based silage supplementation on productive, reproductive performance, and milk microbial qualities.

Carbon and nitrogen sources consumption by ale and lager yeast strains: a comparative study during fermentation.

The rapid and efficient consumption of carbon and nitrogen sources by brewer's yeast is critical for the fermentation process in the brewing industry. The comparison of the growth characterizations of typical ale and lager yeast, as well as their consumption preference to carbon and nitrogen sources were investigated in this study. Results showed that the ale strain grew faster and had a more extended stationary phase than the lager strain. However, the lager strain was more tolerant to the stressful environment in the later stage of fermentation. Meanwhile, the ale and lager yeast strains possessed varying preferences for metabolizing the specific fermentable sugar or free amino acid involved in the wort medium. The lager strain had a strong capacity to synthesize the extracellular invertase required for hydrolyzing sucrose as well as a strong capability to metabolize glucose and fructose. Furthermore, the lager strain had an advantage in consuming Lys, Arg, Val, and Phe, whereas the ale strain had a higher assimilation rate in consuming Tyr. These findings provide valuable insights into selecting the appropriate brewer's yeast strain based on the wort components for the industrial fermentation process. KEY POINTS: • The lager strain is more tolerant to the stressful environment. • The lager strain has the great capability to synthesize the extracellular invertase. • The assimilation efficiency of free amino acid varies between ale and lager.

Study of Brewer's Spent Grain Environmentally Friendly Processing Ways.

BACKGROUND: This article is devoted to the study of the effect of electrochemically activated water (catholyte with pH 9.3) on organic compounds of the plant matrix of brewer's spent grain in order to extract various compounds from it. METHODS: Brewer's spent grain was obtained from barley malt at a pilot plant by mashing the malt followed by filtration and washing of the grain in water and storing it at (0 ± 2) °C in craft bags. For the organic compound quantitative determination, instrumental methods of analysis (HPLC) were used, and the results were subjected to mathematical analysis. RESULTS: The study results showed that at atmospheric pressure, the alkaline properties of the catholyte showed better results compared to aqueous extraction with respect to ß-glucan, sugars, nitrogenous and phenolic compounds, and 120 min was the best period for extraction at 50 °C. The excess pressure conditions used (0.5 ÷ 1 atm) revealed an increase in the accumulation of non-starch polysaccharide and nitrogenous compounds, while the level of sugars, furan and phenolic compounds decreased with increasing treatment duration. The waste grain extract ultrasonic treatment used revealed the effectiveness of catholyte in relation to the extraction of ß-glucan and nitrogenous fractions; however, sugars and phenolic compounds did not significantly accumulate. The correlation method made it possible to reveal the regularities in the formation of furan compounds under the conditions of extraction with the catholyte: Syringic acid had the greatest effect on the formation of 5-OH-methylfurfural at atmospheric pressure and 50 °C and vanillic acid under conditions of excess pressure. Regarding furfural and 5-methylfurfural, amino acids had a direct effect at excess pressure. It was shown that the content of all furan compounds depends on amino acids with thiol groups and gallic acid; the formation of 5-hydroxymethylfurfural and 5-methylfurfural is influenced by gallic and vanillic acids; the release of furfural and 5-methylfurfural is determined by amino acids and gallic acid; excess pressure conditions promote the formation of furan compounds under the action of gallic and lilac acids. CONCLUSIONS: This study showed that a catholyte allows for efficient extraction of carbohydrate, nitrogenous and monophenolic compounds under pressure conditions, while flavonoids require a reduction in extraction time under pressure conditions.

Proteases as Tools for Modulating the Antioxidant Activity and Functionality of the Spent Brewer's Yeast Proteins.

The functionality of the peptides obtained through enzymatic hydrolysis of spent brewer's yeast was investigated. Hydrolysis was carried out for 4-67 h with bromelain, neutrase and trypsin. The resulting hydrolysates were characterized in terms of physical-chemical, antioxidant and techno-functional properties. The solid residues and soluble protein contents increased with the hydrolysis time, the highest values being measured in samples hydrolyzed with neutrase. Regardless of the hydrolysis time, the maximum degree of hydrolysis was measured in the sample hydrolyzed with neutrase, while the lowest was in the sample hydrolyzed with trypsin. The protein hydrolysate obtained with neutrase exhibited the highest DPPH radical scavenging activity (116.9 ± 2.9 µM TE/g dw), followed by the sample hydrolyzed with trypsin (102.8 ± 2.7 µM TE/g dw). Upon ultrafiltration, the fraction of low molecular weight peptides (<3 kDa) released by bromelain presented the highest antioxidant activity (50.06 ± 0.39 µM TE/g dw). The enzymes influenced the foaming properties and the emulsions-forming ability of the hydrolysates. The trypsin ensured the obtaining of proteins hydrolysate with the highest foam overrun and stability. The emulsions based on hydrolysates obtained with neutrase exhibited the highest viscosity at a shear rate over 10 s-1. These results indicate that the investigated proteases are suitable for modulating the overall functionality of the yeast proteins.

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.

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, RCP: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 (t1/2 ) 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 RCP: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 RCP: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.

One-pot synthesis of brewer's spent grain-supported superabsorbent polymer for highly efficient uranium adsorption from wastewater.

High-efficient and fast adsorption of uranium is important to reduce the hazards caused by the uranium contamination of water environment due to the increased human activities. Herein, brewer's spent grain (BSG)-supported superabsorbent polymers (SAP) with different cross-linking densities are prepared as cheap and eco-friendly adsorbents for the first time via one-pot swelling and graft polymerization. A 7 wt% NaOH solution is used to swell BSG before grafting and subsequently neutralize the acrylic acid to control the reaction rate without producing alkaline wastewater. Compared with the traditional methods, swelling improves the grafting density and the utilization of raw materials due to the increased disorder degree of the BSG fibers. This results in the grafting of abundant carboxyl and amide groups onto the BSG backbone, forming a strongly hydrophilic polymer network of the BSG-SAP. Compared with the reference polymers without BSG, BSG-SAP presents higher adsorption capacity and enhanced reusability. The highly cross-linked BSG-SAP (BSG-SAP-H) shows an outstanding adsorption capacity of U(VI) (1465 mg/g at pH0 = 4.6), a fast adsorption rate (81% of equilibrium adsorption capacity in 15 min), and a high selectivity in the presence of competing ions. Adsorption mechanism studies reveal the involvement of amide groups, a bidentate binding structure between UO22+ and the carboxyl groups, and a cation exchange between Na+ and UO22+. More importantly, the adsorption capacity of BSG-SAP-H reaches 254.4 mg/g in the fixed-bed column experiment at a low initial concentration (c0(U) = 30 mg/L) and keeps 80% of the adsorption capacity after four cycles, indicating a great potential for uranium removal from wastewater. This work shows a suitable approach to explore the untreated biomass to prepare SAP with enhanced adsorption performance via a general and low-cost strategy.

Improved osmotic stress tolerance in brewer's yeast induced by wheat gluten peptides.

The influences of three wheat gluten peptides (WGP-LL, WGP-LML, and WGP-LLL) on the osmotic stress tolerance and membrane lipid component in brewer's yeast were investigated. The results demonstrated that the growth and survival of yeast under osmotic stress were enhanced by WGP supplementation. The addition of WGP upregulated the expressions of OLE1 (encoded the delta-9 fatty acid desaturase) and ERG1 (encoded squalene epoxidase) genes under osmotic stress. At the same time, WGP addition enhanced palmitoleic acid (C16:1) content, unsaturated fatty acids/saturated fatty acids ratio, and the amount of ergosterol in yeast cells under osmotic stress. Furthermore, yeast cells in WGP-LL and WGP-LLL groups were more resistant to osmotic stress. WGP-LL and WGP-LLL addition caused 25.08% and 27.02% increase in membrane fluidity, 22.36% and 29.54% reduction in membrane permeability, 18.38% and 14.26% rise in membrane integrity in yeast cells, respectively. In addition, scanning electron microscopy analysis revealed that the addition of WGP was capable of maintaining yeast cell morphology and reducing cell membrane damage under osmotic stress. Thus, alteration of membrane lipid component by WGP was an effective approach for increasing the growth and survival of yeast cells under osmotic stress. KEY POINTS: •WGP addition enhanced cell growth and survival of yeast under osmotic stress. •WGP addition increased unsaturated fatty acids and ergosterol contents in yeast. •WGP supplementation improved membrane homeostasis in yeast at osmotic stress.

Protective effects of peptides on the cell wall structure of yeast under osmotic stress.

Three peptides (LL, LML, and LLL) were used to examine their influences on the osmotic stress tolerance and cell wall properties of brewer's yeast. Results suggested that peptide supplementation improved the osmotic stress tolerance of yeast through enhancing the integrity and stability of the cell wall. Transmission electron micrographs showed that the thickness of yeast cell wall was increased by peptide addition under osmotic stress. Additionally, quantitative analysis of cell wall polysaccharide components in the LL and LLL groups revealed that they had 27.34% and 24.41% higher chitin levels, 25.73% and 22.59% higher mannan levels, and 17.86% and 21.35% higher ß-1,3-glucan levels, respectively, than the control. Furthermore, peptide supplementation could positively modulate the cell wall integrity pathway and up-regulate the expressions of cell wall remodeling-related genes, including FKS1, FKS2, KRE6, MNN9, and CRH1. Thus, these results demonstrated that peptides improved the osmotic stress tolerance of yeast via remodeling the yeast cell wall and reinforcing the structure of the cell wall. KEY POINTS: • Peptide supplementation improved yeast osmotic stress tolerance via cell wall remodeling. • Peptide supplementation enhanced cell wall thickness and stability under osmotic stress. • Peptide supplementation positively modulated the CWI pathway under osmotic stress.

Effect of Added Brewer's Spent Grain on the Baking Value of Flour and the Quality of Wheat Bread.

This study was undertaken to determine the effect of the partial replacement of wheat flour (WF) with barley brewer's spent grain (BBSG) and barley-buckwheat brewer's spent grain (BBSG + B) on dough quality and bread properties, including nutritional value. The contents of brewer's spent grain (BSG) in the blend with wheat flour were 0, 10, and 20%. The quality of the flour blends was assessed with intermediate methods and based on laboratory baking. Analyses were also carried out to determine contents of basic nutrients and energy value. The replacement of part of wheat flour with BBSG and BBSG + B diminished gluten yield and deteriorated its quality (a decreased sedimentation value and stability, and increased dough softening). Changes were also observed in the starch-enzymatic system, resulting in a decreased falling number and maximum paste viscosity. Breads containing both BSG types featured higher yield and lower loaf volume. They had also higher contents of protein, dietary fibre, fat, and ash as well as a lower energy value compared to the wheat bread. Considering the organoleptic traits of breads, the 10% replacement of wheat flour with BSG is recommended in the blend. The BBSG + B was found to elicit more beneficial effects on bread properties than BBSG.

Feeding rice fermented beer waste improves growth performance, nutrient digestibility and nitrogen utilization in growing rabbits.

This study was conducted to investigate the effects of dietary rice brewer waste (RBW) on growth performance, nutrient utilization and nitrogen balance in growing rabbits. Thirty growing rabbits (758 ± 25.7 g initial body weight) were randomly assigned to control and four treatment groups (containing RBW) in a completely randomized design with six rabbits per group. The study lasted 6 weeks for measurements of feed intake and growth performance followed by a five-day metabolic trial to determine nutrient digestibility and nitrogen balance. The five diets contained RBW at 0% RBW (control group), unsterilized RBW at 10% and 20% and sterilized RBW at 10% and 20% in the concentrates. The average daily body weight gain (ADG) in the 20% unsterilized RBW group was higher (p < 0.01) than the control group. No statistically significant difference (p = 0.089) of ADG was observed for the control vs. the sterilized groups, but the overall ADG was better (p = 0.044) in the unsterilized RBW groups than the sterilized RBW groups. The daily dry matter intake in unsterilized and sterilized RBW groups was higher (p < 0.01) than the control group. However, no difference (p = 0.22) was found between the unsterilized and sterilized RBW. The feed conversion ratio (FCR) was lower for the unsterilized RBW groups vs. the control group (p = 0.041), but there was no difference of FCR in the control vs. sterilized RBW groups (p = 0.37) and the unsterilized RBW groups vs. unsterilized RBW groups (p = 0.14). The digestibility of organic matter, crude protein and crude fibre was greater (p < 0.01) in the unsterilized and sterilized RBW groups than the control group. The nitrogen balance and efficiency of nitrogen utilization were also higher in the unsterilized and sterilized RBW groups than the control group (p < 0.01). The study showed that the dietary RBW could improve growth performance and nutrient utilization in growing rabbits with superior responses for the unsterilized RBW.

Brewer's spent yeast replacement in carp diet leads to muscle biomass production, recycling, waste management and resource conservation.

Brewer's spent yeast (BSY) is among the most voluminous by-products generated in brewery industry that adds to the waste; however, smart utilization of BSY could lead to edible biomass production besides waste management. To utilize it for biomass production, it is being used in fish feeds; however, its effect on the fish physiology has been scantily studied. The present study investigated the proteomic changes in muscle tissues of carp Labeo rohita fed with BSY-based diet, to understand its impact on muscle physiology and biomass. Six feeds were prepared with different grades of BSY (0, 20, 30, 40, 50, 100% replacement of fishmeal with BSY) and fishes were fed for 90 days. Highest weight gain%, feed conversion efficiency, specific growth rate% were observed in 30% BSY-replaced group and this group was considered for the proteomic study. Comparative shotgun proteomic analysis was carried out by LC-MS/MS and data generated have been deposited in ProteomeXchange Consortium with dataset identifier PXD020093. A total of 62 proteins showed differential abundance; 29 increased and 33 decreased in the 30% BSY-replaced group. Pathway analysis using IPA and Panther tools revealed that the proteins tyrosine protein kinase, PDGFα, PKRCB and Collagen promote muscle growth by inducing the PI3K-AKT pathway. Conversely, the proteins Serine/threonine-protein phosphatase, Phosphatidylinositol 3,4,5-trisphosphate5-phosphatase 2A and Ras-specific guanine- nucleotide-releasing factor inhibit muscle growth indicating that 30% BSY-replaced feed promote muscle growth in a highly controlled manner. Findings suggest that BSY could be recycled for carp feed production in large scale thereby leading to resource conservation, reducing environmental effects.

Performance, metabolism, and meat quality of broilers fed dry brewery residue.

A study was conducted to assess the chemical composition and apparent metabolizable energy (AME), nitrogen-corrected AME (AMEn), and their respective coefficients of dry brewery residue (DBR) for broilers. A second study was conducted to evaluate the increasing inclusions of DBR in broiler diets and its effects on growth performance, carcass traits, blood metabolites, and meat quality. In the first trial (metabolism assay), a total of 250 male broilers were assigned to 5 diets (0, 100, 200, 300, and 400 g DBR/kg) composed by 5 replications with 10 animals per cage in a completely randomized design in the period from days 11 to 21. There was an increasing linear effect for AME, AMEn, metabolizable coefficient of gross energy (MCGE), and MCGE corrected for N (MCGEn). In the second experiment, a total of 840 one-day-old male broiler chickens were assigned to 6 treatments (0, 20, 40, 60, 80, and 100 g DBR/kg) with 7 replications and 20 animals per pen, from days 0 to 42. Growth performance was determined at days 21 and 42. There was an increasing linear effect for weight gain in the period from days 0 to 21 and for feed intake from days 0 to 42. A linear decreasing effect was observed at day 21 for cholesterol and quadratic effect for uric acid (UA), aspartate aminotransferase, and albumin. At day 42, there was a quadratic effect for UA and creatinine. At day 21, an increasing linear effect was observed for protein deposition rate. In conclusion, the inclusion of DBR up to 100 g/kg improved WG in the starter phase and did not negatively affect the productive parameters of broilers from days 0 to 42.

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.

Spent Brewer's Yeast as a Source of Insoluble ß-Glucans.

In the brewing process, the consumption of resources and the amount of waste generated are high and due to a lot of organic compounds in waste-water, the capacity of natural regeneration of the environment is exceeded. Residual yeast, the second by-product of brewing is considered to have an important chemical composition. An approach with nutritional potential refers to the extraction of bioactive compounds from the yeast cell wall, such as ß-glucans. Concerning the potential food applications with better textural characteristics, spent brewer's yeast glucan has high emulsion stability and water-holding capacity fitting best as a fat replacer in different food matrices. Few studies demonstrate the importance and nutritional role of ß-glucans from brewer's yeast, and even less for spent brewer's yeast, due to additional steps in the extraction process. This review focuses on describing the process of obtaining insoluble ß-glucans (particulate) from spent brewer's yeast and provides an insight into how a by-product from brewing can be converted to potential food applications.

Current extraction techniques towards bioactive compounds from brewer's spent grain - A review.

Background: Brewer's spent grain is one of the most abundant by-products of the brewing industry and is rich in various bioactive compounds (phenolic acids, insoluble dietary fiber and proteins). While at the present brewer's spent grain is mainly used as animal feed its rich nutritional content makes it an interesting alternative for food applications. Scope and approach: As the range of applications of the bioactive compounds extracted from by-products has been growing in recent years, there is the need to obtain and characterize these bioactive compounds. Extraction methods (supercritical carbon dioxide, autohydrolysis, alkaline hydrolysis, solvent extraction, ultrasound assisted extraction, dilute acid hydrolysis, enzymatic hydrolysis, microwave assisted extraction) have been developed and are always being subjected to new approaches to allow better extraction yields of the bioactive compounds. Key findings and conclusions: This review aims to provide a better understanding of the current advantages and limitations of brewer's spent grain extraction processes and to provide a background of brewer's spent grain composition and applications.HighlightsThe re-use of agro-industrial by-products can origin new added-value productsBSG is an agro-industrial by-product and is a source of various bioactive compoundsExtraction methods have been applied to extract these compounds from BSGIt is needed to find new techniques and new possible applications to the BSG.