Evaluation of brewer's spent grain as a substrate for production of hydrolytic enzymes by keratinolytic bacteria

Abstract

BACKGROUND Brewer's spent grain (BSG) is the most abundant by‐product of the brewery industry. The current massive output of BSG requires novel methods of bioconversion into added‐value products. Its composition and high biological value, i.e. high protein content, allows for various biotechnological applications. RESULTS Here, BSG was used as a substrate for submerged cultivation of keratinolytic bacteria, Bacillus cereus PCM 2849 and B. subtilis PCM 2850. The strains biosynthesized proteases to decompose proteins within the substrate and amylases to degrade residual starch. Enzymes degrading structural polysaccharides were also present. Bacillus cereus produced multiple proteases with high activity, predominantly with molecular weight (mw) >70 kDa, depending on the presence of minerals. Bacillus subtilis biosynthesised proteases of wide mw range, independently of the mineral components. Crude culture fluids of both bacteria exhibited proteolytic activity on a variety of proteins, including keratins. Structural deterioration of the BSG in microbial cultures was observed. CONCLUSION The BSG was a suitable medium component for the production of bacterial proteases and polysaccharide‐degrading enzymes. Two keratinolytic Bacilli, grown in the presence of BSG utilized residual proteins and biosynthesized proteases exhibiting keratinolytic activity. Bacillus cereus dominated in terms of protease production, while B. subtilis presented higher production of amylases, cellulases and xylanases. © 2016 Society of Chemical Industry

Enzymatic hydrolysis using bacterial cultures as a novel method for obtaining antioxidant peptides from brewers' spent grain

“…In other research, Łaba et al 17 investigated the impact of BSG medium composition on protease production and protein solubilization in cultures of B. cereus PCM 2849 and B. subtilis PCM 2850. There were significant differences between the two tested strains.…”

Physicochemical Characterization and SEM-EDX Analysis of Brewer’s Spent Grain from the Craft Brewery Industry

“…Hence, the investigation of alternative applications of BSG is important from several perspectives, such as valorization of this coproduct, environmental protection and avoiding disposal problems. The BSG can be used for dietary and nutritional applications [12][13][14][15][16]; as a source of high-value bioproducts e.g., xylitol, lactic acid, xylan, carboxylic acid, arabinoxylans, protein, fermentable sugars, and cellulose nanofibers [6,[17][18][19][20][21][22][23]; for biotechnological processes [24][25][26] and for bioenergy production such as biomethane, co-combustion, bioethanol, pyrolysis, bio-oil, and biohydrogen [27][28][29][30][31][32][33].…”

“…On the other hand, BSG is a source of high-value bioproducts such as antioxidants, monosaccharides, oligosaccharides, xylitol, arabitol, lactic acid, carboxylic acids, emulsifiers, plasticizers, among others [19,35,36]. The spent grain has also been used in biotechnological processes such as a substrate for microorganism culture and enzyme production [24,37]. Another reported process is as a carrier in immobilized-cell systems and as material adsorbent [35].…”

Biosourced Disposable Trays Made of Brewer’s Spent Grain and Potato Starch

“…Brewer’s spent grain (BSG) corresponds to the main by-product of the brewery industry, and comprises insoluble fragments of malt remaining after barley malt mashing and filtration [21,22]. Dried BSG is a lignocellulosic material containing about 192 to 284 g/kg of hemicelluloses (xylose and arabinose), 168 to 254 g/kg of cellulose (glucose), 153 to 247 g/kg of proteins, 119 to 278 g/kg of lignin, and 12 to 46 g/kg of ashes [23].…”