Effect of Carbohydrate Substrate from Starch-Containing Raw Materials on the Composition of Glucans in the Micromycete Aspergillus niger VKPM F-171 Biomass

Abstract

The conditions for biocatalytic cleavage of corn starch and rye whole grain flour for the subsequent cultivation of the Asperillus niger strain VKPM F-171 are described. As a result of this procedure, the amount of water-soluble carbohydrates in the substrates increased by 5-6 times in comparison with the initial raw material, and the content of glucan p-form in the hydrolysate of rye whole grain flour grew by 2-3 times. The content of glucans in the biomass by the end of the cultivation of A. niger VKPM F-171 on corn starch hydrolysate was 28±2% of dry matter, while the proportion of glucans after fermentation on the rye whole grain flour hydrolysate was 21±1%, 96-97% of which were β-glucans. The hydrolysis with Trichoderma longibrachiatum β-glucanase and Trichoderma reesei xylanase resulted in a 1.1-1.2-fold increase in the proportion of soluble carbohydrates in microbial biomass. It was found via gas-liquid chromatography that the structural units of carbohydrates in microbial biomass are represented by glucose and its 2- and 6-deoxy derivatives, fructose, fucose, galactose, mannose, xylose, and, to the greatest extent, by the reserve saccharide sedoheptulose. It was established that β-glucans are products of hydrolysis of the chitin-glucan complex and glycopeptides. The molecular weight of the obtained microbial glucan-containing biopolymers ranges from 0.5 to 50 kDa. It was shown that the content of β-glucans in microbial biomass allows the latter to be considered as an alternative to plant sources. biosynthesis, Asperillus niger, biocatalysis, starch-containing raw materials, glucans