Subcritical water treatment to modify insoluble dietary fibers from brewer's spent grain for improved functionality and gut fermentability

Lactic acid (LA)-assisted subcritical water treatment (SWT) was applied to modify the insoluble dietary fiber (IDF) from brewer's spent grain (BSG) for enhancing its functionality and gut fermentability. Modified IDFs were thoroughly characterized for their chemical and structural properties. The results revealed that increasing the treatment temperature and LA concentration reduced hemicellulose content in IDFs from 38.4 % to 0.7 %, alongside a decreased yield (84.8 %-51.4 %), reduced particle size (519.8-288.6 μm), and more porous structure of IDFs. These modifications were linked to improved functionalities, evidenced by the highest water and oil holding capacity increasing by 36 % and 67 %, respectively. Remarkably, the highest glucose adsorption capacity increased by 6.5 folds. Notably, modified IDFs exhibited slower in-vitro fermentation, elevated short-chain fatty acids (SCFAs) production, and a higher proportion of butyrate in SCFAs. These findings highlight the potential of LA-assisted SWT in transforming BSG-derived IDF into a valuable functional food ingredient.

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

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

Production of single cell protein from brewer's spent grain through enzymatic saccharification and fermentation enhanced by ammoniation pretreatment

Brewer's spent grain (BSG) is a major low-value by-product of beer industry. To realize the high value application of BSG, this work proposed a strategy to produce single cell protein (SCP) with oligosaccharide prebiotics from BSG, via ammoniation pretreatment, enzymatic hydrolysis, and fermentation. The optimum conditions of ammoniation pretreatment obtained by response surface method were 11 % ammonia dosage (w/w), 63 °C for 26 h. Suitable enzyme and yeast were screened to enhance the conversion of cellulose and hemicellulose in BSG into sugars and maximize the SCP yield. It was shown that using lignocellulolytic enzyme SP from Penicillium oxalicum and Trichosporon cutaneum, about 310 g of SCP with 80 g of arabinoxylo-oligosaccharides were obtained from 1000 g of BSG. This process is low cost, high efficiency, and easy to implement, which has good industrial application prospects.

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.

Increased Production of γ-Aminobutyric Acid from Brewer's Spent Grain Through Bacillus Fermentation

Brewer's spent grain (BSG) is a waste product of the beer industry, and γ-aminobutyric acid (GABA) is a physiologically active substance important for brain and neuron physiology. In this study, we used the bacterial strains Bacillus velezensis DMB06 and B. licheniformis 0DA23-1, respectively, to ferment BSG and produce GABA. The GABA biosynthesis pathways were identified through genomic analysis of the genomes of both strains. We then inoculated the strains into BSG to determine changes in pH, acidity, reducing sugar content, amino-type nitrogen content, and GABA production, which was approximately doubled in BSG inoculated with Bacillus compared to that in uninoculated BSG; however, no significant difference was observed in GABA production between the two bacterial strains. These results provide the experimental basis for expanding the use of BSG by demonstrating the potential gain in increasing GABA production from a waste resource.

Surface ion-imprinted brewer's spent grain with low template loading for selective uranyl ions adsorption from simulated wastewater

Efficient removal of uranyl ions from wastewater requires excellent selectivity of the adsorbents. Herein, we report a new strategy using a high monomer/template molar ratio of 500:1 to prepare surface ion-imprinted brewer's spent grain (IIP-BSG) for selective U(VI) removal using binary functional monomers (2-hydroxyethyl methacrylate and diethyl vinylphosphonate) with high site accessibility and easy template removal. IIP-BSG exhibits a maximum U(VI) adsorption capacity of 165.7 mg/g, a high selectivity toward U(VI) in the presence of an excess amount of Eu(III) (Eu/U molar ratio = 20), a good tolerance of salinity, and a high reusability. In addition, mechanism studies have revealed electrostatic interaction and a coordination of uranyl ions by carboxyl and phosphoryl groups, the predominant contribution of high-energy (specific) sites during selective adsorption, and internal mass transfer as the rate-controlling step of U(VI) adsorption. Furthermore, IIP-BSG shows great potentials to separate U(VI) from lanthanides in simulated nuclear wastewater (pH₀ = 3.5) and selectively concentrate U(VI) from simulated mine water (pH₀ = 7.1). This study proves that the ion-imprinting effect can be achieved using a very low template amount with reduced production cost and secondary pollution, which benefits large-scale promotion of the ion-imprinted materials for selective uranyl ions removal.

Aqueous ethanol organosolv process for the valorization of Brewer's spent grain (BSG)

Brewers spent grain (BSG), the main solid byproduct of brewing, is annually generated by ca 37 million tons worldwide, which due to limited application, mostly ends up in landfills. This study aims to separate BSG's fractions (lignin, cellulose, and hemicellulose) by ethanol organosolv pretreatment. Lignin-rich fractions were recovered using a two-step separation technique. The effects of temperature, retention time, and ethanol concentration on the quantity and quality of fractions were studied. The temperature considerably impacted the quality and quantity of obtained fractions, while other parameter effects greatly depended on the temperature. Substantial hemicellulose removal (90 %) along with lignin removal (56 %) and recovery (57 %) were obtained at 180 °C. The highest lignin purity (95 %) was obtained at the pretreatment conditions of 180 °C, 120 min, and 50 % ethanol concentration. This work provides an alternative route for BSG utilization, mitigating its environmental impact while enhancing the economy of a brewery.

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

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

Impact of the use of pressurized liquids on the extraction and functionality of proteins and bioactives from brewer's spent grain

A green methodology based on pressurized liquids (PLE) to extract proteins and obtain highly active extracts from brewer's spent grain (BSG) is proposed. Box-Behnken experimental design was employed to study the effect of extraction parameters on the protein content (PC), the total phenolic content (TPC), and the antioxidant activity of extracts. Results were compared with those obtained by conventional alkaline extraction assisted with ultrasounds (UAE). The selection of PLE conditions enabled to tailor the PC and TPC of extracts. PLE extracted 36 % more proteins than UAE. PLE extracts showed higher antioxidant, cholesterol esterase inhibition, and ACE inhibitory activities than UAE extract. HPLC-MS/MS enabled to observe that the extraction technique and experimental conditions significantly affected to the kind and amount of extracted proteins, and released peptides, and phenolic compounds. A higher ratio of hydrophobic peptides was observed in PLE extracts, which justified their higher bioactivity.

An evaluation of sonication pretreatment for enhancing saccharification of brewers' spent grain

This paper deals with the investigation of ultrasound (US) pretreatment of brewer's spent grain (BSG) as a means of releasing fermentable sugars, and the subsequent production of ethanol from this lignocellulosic biomass. Using response surface methodology (RSM), the influence of US power, time, temperature and biomass loading on fermentable sugar yield from BSG was studied. The optimal conditions were found to be 20% US power, 60 min, 26.3 °C, and 17.3% w/v of biomass in water. Under these conditions, an approximate 2.1-fold increase in reducing sugar yield (325 ± 6 mg/g of biomass) was achieved, relative to untreated BSG (151.1 ± 10 mg/g of biomass). In contrast to acid or alkaline pretreatment approaches, the use of water obviated the need for neutralization for the recovery of sugars. The characterization of native and pretreated BSG was performed by HPLC, FTIR, SEM and DSC. Fermentation studies using S. cerevisiae growing on pretreated BSG resulted in a conversion of 66% of the total sugar content ininto ethanol with an ethanol content of 17.73 ± 2 g/ 100 g of pretreated BSG. These results suggest that ultrasound pretreatment is a promising technology for increased valorization of BSG as a feedstock for production of bioethanol, and points ton the need for further work in this area.

Effect of protein during hydrothermal carbonization of brewer's spent grain

This study has two targets: Studying the extraction of the initial protein content from brewer's spent grain and the impact of protein's extraction on the chemical-physical properties of produced hydrochars. The protein was extracted from brewer's spent grains using the pH-shifting method. The extracted protein was quantified and characterized by their amino acid profile. The hydrothermal treatment was applied at 190 °C and 220 °C for 0.5 h, 1 h, 2 h, and 4 h. The hydrochars and process water were collected and assayed. The hydrochar after protein extraction reveals the lowest yield to hydrochars (67.10-45.14%), higher C/N ratio (19.66-21.33) and lower ash content (1.52-1.72 wt%) compared to the hydrochar without extraction.

Improving enzymatic hydrolysis of brewer spent grain with nonthermal plasma

In this study, a new pre-treatment method based on novel non-thermal plasma technology was developed to improve the enzymatic hydrolysis of brewer's spent grain (BSG) and subsequent bioethanol production. A submerged dielectric barrier discharge plasma reactor system was applied for this purpose. Pre-treatments were performed by taking into account variables including; voltages (22 kV, 25 kV and 28 kV), solvent (acid, alkali and water) and time (5, 10, 15 min). The resulting treated biomass was subjected to enzymatic hydrolysis. A 2.14-fold increase in yield of the reducing sugar was achieved post hydrolysis when the biomass was treated in water for 10 min at a voltage setting of 28 kV (162.90 mg/g of BSG) compared to control (75.94 mg/g of BSG). This research suggests that subjecting lignocellulose to plasma discharges can enhance the efficiency of enzymatic hydrolysis. A high ethanol titre was also obtained upon fermentation of the hydrolysate (25.062 g/l).

Natural Red Pigment Production by Monascus Purpureus in Submerged Fermentation Systems Using a Food Industry Waste: Brewer's Spent Grain

This paper studies the production of natural red pigments by Monascus purpureus CMU001 in the submerged fermentation system using a brewery waste hydrolysate, brewer's spent grain (BSG). The chemical, structural and elemental characterization of the BSG was performed with Van-Soest method, Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. The lignocellulosic structure of BSG was hydrolyzed with a dilute sulfuric acid solution (2% (w/v)) followed by detoxification with Ca(OH)2. Maximum red pigment production (22.25 UA500) was achieved with the following conditions: 350 rpm shake speed, 50 mL fermentation volume, initial pH of 6.5, inoculation ratio of 2% (v/v), and monosodium glutamate (MSG) as the most effective nitrogen source. Plackett-Burman design was used to assess the significance of the fermentation medium components, and MSG and ZnSO4·7H2O were found to be the significant medium variables. This study is the first study showing the compatibility of BSG hydrolysate to red pigment production by Monascus purpureus in a submerged fermentation system.

Enzymatic hydrolysis of brewer's spent grain to obtain fermentable sugars

Lignocellulosic biomass is a feedstock with the potential to be converted into value-added bioproducts. The use of enzymatic hydrolysis allows the cleavage of lignocellulose into their monomeric units, but there are some drawbacks that make its use in industrial biocatalysis unfeasible. In the present study, we describe the hydrolysis of brewer's spent grain (BSG) with an enzymatic cocktail produced by Aspergillus niger CECT 2700 and its comparison with commercial enzymes. In addition, it was determined whether pretreating the BSG (non-pressurized alkaline hydrolysis or treatment with cholinium glycinate ionic liquid) is necessary. Results show that both pretreatments enhanced xylose release (10.55 ± 0.07 g/L and 8.14 ± 0.13 g/L respectively), meanwhile the hydrolysis of raw BSG with the enzymatic cocktail produced solutions containing high levels of glucose (18.45 ± 1.66 g/L) and xylose (6.38 ± 0.26 g/L).

Utilization of brewing and malting by-products as carrier and raw materials in l-(+)-lactic acid production and feed application

Application of agro-industrial by-products for the production of lactic acid was studied in this paper. Brewer's spent grain (BSG), malt rootlets (MR), brewer's yeast (BY), and soy lecithin (SL) were used as raw materials in L-(+)-LA fermentation by free and immobilized Lactobacillus rhamnosus ATCC 7469. The BSG, solid remains after BSG and MR hydrolysis (BSGMRSR), and MR were evaluated as carriers for batch and repeated batch fermentations with immobilized cells. During batch fermentations with immobilized cells, high cell viability (10 to 11 log CFU/g) was achieved on all carriers. In batch fermentation with BSG as a carrier, the highest LA yield of 93.79% and volumetric productivity of 1.15 g/L/h were obtained. Furthermore, very high LA yield (95.46%), volumetric productivity (1.98 g/L/h) and L. rhamnosus viability (11.5 log CFU/g) were achieved in repeated batch fermentations with the cells immobilized on this carrier. The immobilized cells showed high survival rate (94-95%) during exposure to simulated gut condition. Based on the analysis of BSGMRSR, and BY solid remains, and on in vitro evaluation of the probiotic characteristics of immobilized cells, it was observed that they could satisfy the recommendations for high-quality feed preparation.

Valorization of Brewers' Spent Grain for the Production of Lipids by Oleaginous Yeast

Brewers’ spent grain (BSG) accounts for 85% of the total amount of by-products generated by the brewing industries. BSG is a lignocellulosic biomass that is rich in proteins, lipids, minerals, and vitamins. In the present study, BSG was subjected to pretreatment by two different methods (microwave assisted alkaline pretreatment and organosolv) and was evaluated for the liberation of glucose and xylose during enzymatic saccharification trials. The highest amount of glucose (46.45 ± 1.43 g/L) and xylose (25.15 ± 1.36 g/L) were observed after enzymatic saccharification of the organosolv pretreated BSG. The glucose and xylose yield for the microwave assisted alkaline pretreated BSG were 34.86 ± 1.27 g/L and 16.54 ± 2.1 g/L, respectively. The hydrolysates from the organosolv pretreated BSG were used as substrate for the cultivation of the oleaginous yeast Rhodosporidium toruloides, aiming to produce microbial lipids. The yeast synthesized as high as 18.44 ± 0.96 g/L of cell dry weight and 10.41 ± 0.34 g/L lipids (lipid content of 56.45 ± 0.76%) when cultivated on BSG hydrolysate with a C/N ratio of 500. The cell dry weight, total lipid concentration and lipid content were higher compared to the results obtained when grown on synthetic media containing glucose, xylose or mixture of glucose and xylose. To the best of our knowledge, this is the first report using hydrolysates of organosolv pretreated BSG for the growth and lipid production of oleaginous yeast in literature. The lipid profile of this oleaginous yeast showed similar fatty acid contents to vegetable oils, which can result in good biodiesel properties of the produced biodiesel.

Possibility of L-(+)-lactic acid fermentation using malting, brewing, and oil production by-products

Industrial by-products such as brewer's spent grain (BSG) hydrolysate, malt rootlets extract (MRE) and soybean meal extract (SME) were used for L-(+) lactic acid (LA) production by a pure L. rhamnosus ATCC 7469 strain. The effect of the addition of MRE (10-50%) or SME (10-50%) in BSG hydrolysate on batch and fed-batch LA fermentation was evaluated. The addition of MRE and SME increased the concentration of free amino nitrogen (FAN) and essential minerals (Fe, Mg, Mn, and Zn), which had a positive effect on the fermentation. Also, the MRE addition significantly lowered C/N ration to a more favorable level for the efficient LA fermentation. In batch fermentation, the highest LA concentration (25.73 g/L), yield (86.31%), and volumetric productivity (0.95 g/L h^-1), were obtained with the addition of 50% MRE. Further increase in LA concentration to 58.01 g/L, yield to 88.54%, and volumetric productivity to 1.19 g/L h^-1 was achieved in fed-batch fermentation with addition of 50% MRE. A high optical purity of LA with 99.7% of L-(+)-isomer was obtained on the substrate based on industrial by-products. In addition, solid remains after BSG hydrolysis and MRE and SME preparation, together with the biomass of L. rhamnosus separated after the fermentation could be a good base for feed preparation.

Enhanced cesium removal from real matrices by nickel-hexacyanoferrate modified activated carbons

After nuclear disasters, radioactive cesium partitions to soils and surface water, where it decays slowly. Hexacyanoferrates (HCFs) have excellent cesium removal properties but their structure is typically powdery. Many carrier materials, such as biomass or magnetic particles, have been used to provide a suitable substrate for HCFs that can be used in filters. This research uses the sorption properties of activated carbon (AC) to incorporate Ni-HCF, resulting in good structural properties of the hybrid material. These HCF-modified ACs show drastically improved sorption properties towards Cs after one, two and three HCF impregnation cycles. The activated carbon from brewer's spent grain with one modification cycle removes more than 80% of 1 mg L^-1 Cs in a sea water solution and more than 98% of 1 mg L^-1 Cs from surface water at a low AC dosage (0.5 g L^-1). Iron and nickel leaching is studied and found to be dependent on the type of modified AC used and the leaching solution. Iron leaching can be problematic in surface and seawater, whereas nickel leaching is especially pronounced in seawater.

Valorization of Brewer's spent grain to prebiotic oligosaccharide: Production, xylanase catalyzed hydrolysis, in-vitro evaluation with probiotic strains and in a batch human fecal fermentation model

Brewer's spent grain (BSG) accounts for around 85% of the solid by-products from beer production. BSG was first extracted to obtain water-soluble arabinoxylan (AX). Using subsequent alkali extraction (0.5 M KOH) it was possible to dissolve additional AX. In total, about 57% of the AX in BSG was extracted with the purity of 45-55%. After comparison of nine xylanases, Pentopan mono BG, a GH11 enzyme, was selected for hydrolysis of the extracts to oligosaccharides with minimal formation of monosaccharides. Growth of Bifidobacterium adolescentis (ATCC 15703) was promoted by the enzymatic hydrolysis to arabinoxylooligosaccharides, while Lactobacillus brevis (DSMZ 1264) utilized only unsubstituted xylooligosaccharides. Furthermore, utilization of the hydrolysates by human gut microbiota was also assessed in a batch human fecal fermentation model. Results revealed that the rates of fermentation of the BSG hydrolysates by human gut microbiota were similar to that of commercial prebiotic fructooligosaccharides, while inulin was fermented at a slower rate. In summary, a sustainable process to valorize BSG to functional food ingredients has been proposed.

A comparative analysis of pretreatment strategies on the properties and hydrolysis of brewers' spent grain

In this study, brewer's spent grain (BSG) was subjected to a range pretreatments to study the effect on reducing sugar yield. Glucose and xylose were found to be the predominant sugars in BSG. Brewers spent grain was high in cellulose (19.21g/100g of BSG) and lignin content (30.84g/100g of BSG). Microwave assisted alkali (MAA) pretreatment was found to be the most effective pretreatment for BSG, where the pretreatment was conducted at 400W for 60s. A maximum reducing yield was observed with high biomass loading (1g/10ml), cellulase (158.76μl/10ml), hemicellulase (153.3μl/10ml), pH (5.4) and an incubation time (120h). Upon enzymatic hydrolysis, MAA pretreated BSG yielded 228.25mg of reducing sugar/g of BSG which was 2.86-fold higher compared to native BSG (79.67mg/g of BSG); simultaneously BSG was de-lignified significantly. The changes in functional groups, crystallinity and thermal behaviour was studies by means of FTIR, XRD and DSC, respectively.

Effects of process parameters on the properties of barley containing snacks enriched with brewer's spent grain

Brewer's spent grain (BSG), a by-product of malting of barley in the production of malt extract, was used as an ingredient in extruded barley-based snacks in order to improve the nutritional value of the snacks and widen the applications of this by-product in food sector. The effects of the extrusion parameters on the selected properties of the snacks were studied. Snacks with different ingredients including whole grain barley flour, BSG, whey protein isolate (WPI), barley starch and waxy corn starch were produced in 5 separate trials using a co-rotating twin-screw extruder. Extrusion parameters were water content of the mass (17-23 %), screw speed (200-500 rpm) and temperature of the last section and die (110-150 °C). Expansion, hardness and water content of the snacks were determined. Snacks containing barley flour and BSG (10 % of solids) had small expansion and high hardness. Addition of WPI (20 % of solids) increased expansion only slightly. Snacks with high expansion and small hardness were obtained when part of the barley flour was replaced with starch (barley or waxy corn). Yet, the highest expansion and the smallest hardness were achieved when barley flour was used with barley starch and WPI without BSG. Furthermore, expansion increased by increasing screw speed and decreasing water content of the mass in most of the trials. This study showed that BSG is a suitable material for extruded snacks rich in dietary fiber. Physical properties of the snacks could be improved by using barley or waxy corn starch and WPI.

Organic breakdown products resulting from hydrothermal carbonization of brewer's spent grain

Hydrothermal carbonization of brewer's spent grain resulted in a solid hydrochar and an aqueous phase rich in macromolecular dissolved organic matter. Both phases were analyzed with regard to low molecular weight organic compounds (MW<500 Da) in lyophilized form by exhaustive solvent extraction followed by pre-chromatographic derivatization and GC/MS-analysis. Low molecular weight acids, O-functionalized phenols, cyclopentenone derivatives, and benzenediols accounted for the majority of organic analytes in both hydrothermal carbonization product streams while being absent in solvent extracts of the pristine biomass. The pattern of short chain functionalized acids in the pristine biomass and in the hydrothermally produced matrices turned out very different. Acylglycerines as the most abundant lipids in pristine brewer's spent grain were quantitatively hydrolyzed under hydrothermal conditions. The recovery of total fatty acids present in the pristine biomass amounted to 19%. The major fraction of hydrophobic breakdown products including fatty acids, fatty alcohols, and sterols was sorbed onto the hydrochar.

Improved efficiency of brewer's spent grain arabinoxylans by ultrasound-assisted extraction

Arabinoxylan (AX) rich extracts from brewer's spent grain (BSG) were produced by the application of ultrasound-assisted extraction (UAE) and conventional alkaline extraction (AKE). UAE and AKE were optimised for the production of the highest yield of ethanol insoluble material using response surface methodology (RSM). The efficiency of UAE was established by the significant reduction of time (7h to 25 min) and energy when compared to AKE, to recover similar amounts of AX (60%) from BSG, leading to the production of starch-free AX-rich extracts.

Carboxylic acid production from brewer's spent grain via mixed culture fermentation

This study aimed at investigating carboxylic acid production from brewer's spent grain (BSG) via mixed culture fermentation. The results showed that the distribution of fermentation products was significantly affected by pH conditions and the addition of electron donors. Lactic acid was the dominant component under acidic and alkaline conditions while volatile fatty acids (VFAs) became dominant under the neutral condition. Furthermore, the neutral condition favored the chain elongation of carboxylic acids, especially with ethanol as the electron donor. Ethanol addition enhanced valeric acid and caproic acid production by 44% and 167%, respectively. Lactic acid addition also had positive effects on VFAs production under the neutral condition but limited to C2-C4 products. As a result, propionic acid and butyric acid production was increased by 109% and 152%, respectively. These findings provide substantial evidence for regulating carboxylic acid production during mixed culture fermentation of BSG by controlling pH and adding electron donors.

Characterization of biocoals and dissolved organic matter phases obtained upon hydrothermal carbonization of brewer's spent grain

The wet biomass brewer's spent grain was subjected to hydrothermal carbonization to produce biocoal. Mass balance considerations indicate for about two thirds of the organic carbon of the input biomass to be transferred into the biocoal. The van Krevelen plot refers to a high degree of defunctionalization with decarboxylation prevailing over dehydration. Calorific data revealed a significant energy densification of biocoals as compared to the input substrate. Sorption coefficients of organic analytes covering a wide range of hydrophobicities and polarities on biocoal were similar to those for dissolved humic acids. Data from GC/MS analysis indicated that phenols and benzenediols along with fatty acids released from bound lipids during the hydrothermal process constituted abundant products. Our findings demonstrate that the brewer's spent grain by-product is a good feedstock for hydrothermal carbonization to produce biocoal, the latter offering good prospects for energetic and soil-improving application fields.

"A comparison between sugar consumption and ethanol production in wort by immobilized Saccharomyces Cerevisiae, Saccharomyces Ludwigii and Saccharomyces Rouxii on Brewer'S Spent Grain"

The immobilization of Saccharomyces cerevisiae DSM 70424, Saccharomyces ludwigii DSM 3447 and Saccharomyces rouxii DSM 2531 on brewer’s spent grain and then ethanol production and sugar consumption of these immobilized yeasts were investigated. The aim of this study was to investigate the abilities of these three immobilized yeasts for producing alcohol for brewing at two temperatures (7 and 12 °C) using two different sugar levels (one at original level supplied in the brewery and one with 2.5% (w/v), added glucose to the wort).

Increasing both parameters resulted in higher alcohol production by all the yeasts studied. At 7 °C and with original wort density the ethanol content at the end of fermentation was 2.7% (v/v) for S. cerevisiae, 1.7% for S. ludwigii and 2.0% for S. rouxii. After the addition of 2.5% (w/v) glucose at the same temperature (7 °C), the alcohol production was increased to 4.1, 2.8 and 4.1%, respectively. Similar improvements were observed when the fermentation was carried out at 12 °C with/without the addition of glucose to the wort. However, temperature indicated greater influence on S. ludwigii than did on S. rouxii and S. cerevisiae. The immobilization as carried out in this study impacted both S. ludwigii and S. rouxii in a way that they could consume maltose under certain conditions.