Brewers’ spent grain as substrate for dextran biosynthesis by Leuconostoc pseudomesenteroides DSM20193 and Weissella confusa A16

Abstract

Background Lactic acid bacteria can synthesize dextran and oligosaccharides with different functionality, depending on the strain and fermentation conditions. As natural structure-forming agent, dextran has proven useful as food additive, improving the properties of several raw materials with poor technological quality, such as cereal by-products, fiber-and protein-rich matrices, enabling their use in food applications. In this study, we assessed dextran biosynthesis in situ during fermentation of brewers´ spent grain (BSG), the main by-product of beer brewing industry, with Leuconostoc pseudomesenteroides DSM20193 and Weissella confusa A16. The starters performance and the primary metabolites formed during 24 h of fermentation with and without 4% sucrose (w/w) were followed. Results The starters showed similar growth and acidification kinetics, but different sugar utilization, especially in presence of sucrose. Viscosity increase in fermented BSG containing sucrose occurred first after 10 h, and it kept increasing until 24 h concomitantly with dextran formation. Dextran content after 24 h was approximately 1% on the total weight of the BSG. Oligosaccharides with different degree of polymerization were formed together with dextran from 10 to 24 h. Three dextransucrase genes were identified in L. pseudomesenteroides DSM20193, one of which was significantly upregulated and remained active throughout the fermentation time. One dextransucrase gene was identified in W. confusa A16 also showing a typical induction profile, with highest upregulation at 10 h. Conclusions Selected lactic acid bacteria starters produced significant amount of dextran in brewers’ spent grain while forming oligosaccharides with different degree of polymerization. Putative dextransucrase genes identified in the starters showed a typical induction profile. Formation of dextran and oligosaccharides in BSG during lactic acid bacteria fermentation can be tailored to achieve specific technological properties of this raw material, contributing to its reintegration into the food chain.

Sustainable Applications for the Valorization of Cereal Processing By-Products

“…The proteins of barley, wheat, corn, and rice processing by-products have better functional properties compared to those of the endosperm due to their content in essential amino acids and their valorization potential in the market of extruded and cereal-based baked products is high [ 18 , 55 ]. The fermentation of BSG with different lactic acid bacteria (e.g., with Leuconostoc pseudomesenteroides DSM20193 and Weissella confusa A16 as suggested by Koirola et al [ 56 ]) has been examined in different applications such as yoghurt [ 57 ], pasta [ 58 ] and bread [ 59 ].…”

Production of Sucrolytic Enzyme by Bacillus licheniformis by the Bioconversion of Pomelo Albedo as a Carbon Source

“…The pH stability was accorded to the residual sucrolytic activity after allowing the sleTKU004 solution to stand at different pH points for 1 h at 20 • C. Each experiment was performed in triplicate. 4 , and EDTA were tested at the final concentration of 1 mM, 5 mM, and 10 mM whereas Tween 20, Tween 40, Triton X-100, and SDS were assessed at 1%, 5%, and 10% concentrations. Each experiment was performed in triplicate.…”

“…Sucrose hydrolysis is catalyzed by sucrolytic enzymes to produce a mixture of glucose and fructose (also known as invert sugar). Sucrolytic enzymes are of various types such as invertases (sucrases) [2], levansucrases [3], dextransucrases [4], glucansucrases [5], and inulosucrases [6]. They use sucrose as the donor of fructosyl moiety to be transferred to various kinds of acceptors, such as water (sucrose hydrolysis), sucrose, and fructan [7].…”

How water‐soluble saccharides drive the metabolism of lactic acid bacteria during fermentation of brewers' spent grain

“…Recently, BSG fermentation with Lactiplantibacillus plantarum under liquid or semi‐liquid conditions was shown to promote the release of bioactive compounds (Verni et al ., 2020 ). A BSG/water mixture was also proposed as suitable substrate for dextran biosynthesis by Leuconostoc pseudomesenteroides and Weissella confusa strains (Koirala et al ., 2021 ). Conversion of lignocellulosic substrate to value‐added chemicals comprises two main steps: (i) the pre‐treatment and the enzymatic hydrolysis to obtain fermentable sugars; and (ii) the fermentation process to produce/release valuable compounds.…”

“…pseudomesenteroides to environmental pressure induced by BSG water‐soluble saccharides. Capability of both species to grow on BSG‐derived substrates was previously reported (Verni et al ., 2020 ; Koirala et al ., 2021 ). The ‘phenotype switching’ is a novel concept concerning the assessment of how the bacterial metabolism behaves in growth models (e.g.…”