Methane Production Using Brewery Spent Grain: Optimal Hydrothermolysis, Fermentation of Waste and Role of Microbial Populations

Abstract

The hydrothermolysis variables temperature (150 -210 °C) and time (10 -20 minutes) were assessed to improve hydrolysis e ciency of brewery spent grain (BSG) for renewable energy generation. The intensi cation of the pretreatment was expressed by the severity variation (2.8 -4.5) and the process was optimized with methane production of 411.6 ± 7.2 mL. g -1 STV (severity 4.2). The fermentationmethanogenesis of BSG and hydrolysate resulting from BSG hydrothermolysis process under severity of 4.2 (210 o C for 10 min.) was evaluated by central composite design (CCD) with the variables operation temperature (30 -60 °C), BSG concentration (7.3 -20.7 g.L -1 ) and hydrolysate (0 -12.4 mL). The higher methane production observed was 305.8 mL.g -1 STV, with 14 g.L -1 of BSG, without hydrolysate at 45 °C.The main soluble metabolites were acetic acid (233.17 mg.L -1 ) and butyric acid (156.0 mg.L -1 ). On other hand, the lower methane production (108.5 ± 2.0 mL. g -1 STV) veri ed was 14 g.L -1 of BSG, 6.5 mL of hydrolysate at 60 °C, which revealed that in this condition propionic acid (947.4 mg.L -1 ) and acetic acid (599.2 mg.L -1 ) were expressive. In the optimal fermentation-methanogenic condition of pretreated BSG, Macellibacteroides and Sphaerochaeta (15.9 and 14.7%, respectively) were identi ed, as well as archaea similar to Methanosaeta (80.4%), favoring the acetoclastic methanogenic pathway.

Evaluating the performance of an integrated membrane-aerated biofilm reactor (MABR) system for high-strength brewery wastewater treatment

“…Sphaerochaeta , 35 Bacteroides 36 and Macellibacteroides are 37 are fermentative microbes that can consume organic compounds such as starch, textile, and protein and produce volatile organic acids, predominantly acetate, formate, and butyrate. The aforementioned taxa have been reported to coexist in anaerobic systems of brewery grain fermentation 38 and raw textile effluent treatment. 39 On the other hand, Prevotella , Caproiciproducens and Ruminiclostridium were found to be beneficial together for the degradation of polysaccharides and protein, such as cellulose and hemicellulose and contribute to the acidification process.…”

Valorization of Brewers’ Spent Grains: Pretreatments and Fermentation, a Review

“…Therefore, breaking down the spent grains into their constituents will yield a number of value-added components including carbohydrates and proteins, which constitute a suitable medium or substrate for the fermentative production of various bioactive compounds [18]. Consequently, pretreatments will prepare the lignocellulosic substrate for microbial activity, making it more accessible to the microbial consortium [19]. These pretreatments will break cellulose into glucose and hemicellulose into mainly xylose and arabinose, which are the most abundant monosaccharides present in the hydrolyzed spent grains [20].…”

“…A study done by Gomes et al reported that hydrothermolysis led to a 10% increase in methane production from BSG. Particularly, 467.6 NmL/g methane was produced by a pretreated sample (hydrothermolysis at 140 • C for 15 min) compared to 409.8 NmL/g produced by the unpretreated sample [19]. Finally, ultrasonic pretreatment holds potential for large-scale processes.…”

“…Particularly, using biomass from agro-industrial waste materials as a substrate in these biotechnological applications, to produce microbial cell biomass and to grow different fungi without the need for extra nutrients, has been at the center of attention [8]. Due to the high nutritional value of BSG, mainly its high hemicellulose content ranging between 19 and 42% [19], this secondary raw material can produce through fermentation several value-added products, such as organic acids, amino acids, volatile fatty acids, enzymes, vitamins, second-generation biofuels and other products [23,39]. For instance, a study done by Marcus and Fox reported that BSG can be processed into various enzymes, including α-amylase, β-amylase, cellulases, glucanases, hemicellulases, etc., and to other products such as xylitol, bioethanol, and citric acid through fungal fermentation of BSG [40].…”

Bio-based agricultural products: a sustainable alternative to agrochemicals for promoting a circular economy

“…84 Hydrothermolysis is performed at 150°C–210 °C for a period (10–20 minutes), which accelerates the rate of OW degradation. 85…”