Valorization of soybean meal to produce high-protein animal feed and value-added products using a new strain of Aureobasidium pullulans

Soybean meal (SBM) is a by-product of soybean oil production. It is a high-quality protein supplement for animal feed. However, it is rich in anti-nutritive factors and indigestible components, among which the special attention is focused on galacto-oligosaccharides, due to the lack of ?-galactosidase in monogastric animals. The main goal of this study was to apply fermentation using a selected strain of black yeast-like fungus of the SBM to obtain a high-protein, low-oligosaccharide soy-based product. Screening for an appropriate strain of Aureobasidium spp. among natural isolates from grapes has been performed. The highest ?-galactosidase activity of 0.89 U cm-3 was produced by the strain identified as A. pullulans P8. It was applied in SBM submerged (SmF) and solid-state fermentations (SSF). Maximal crude protein yield (~61 % based on dry weight) and the lowest galacto-oligosaccharides content were obtained after 3 days of SmF at 30?C and 10 % of dry matter. SSF produced ~58 % crude protein after 7 days of incubation at 30?C with substrate containing 30 % of dry matter. Extracellular enzymatic activities of cellulase, pectinase, amylase, xylanase, and ?-galactosidase were detected in the supernatant after SmF, indicating its potential for hydrolysis of various lignocellulosic biomass substrates.