Solid-state cultivation of recombinant Aspergillus nidulans to co-produce xylanase, arabinofuranosidase, and xylooligosaccharides from soybean fibre

Solid-state cultivations of genetically modified strains of Aspergillus nidulans A773, using soybean fibre as substrate, were carried out to produce xylanase and arabinofuranosidase, and these enzymes were subsequently used to obtain xylooligosaccharides using the same agro-residue. First, the best fungi cultivation conditions (moisture content, pH, temperature and addition of maltose) were optimized one-by-one for obtain the crude enzyme extracts. Subsequently, the application of xylanase on soybean fibre to obtain xylooligosaccharides was optimized by central composite design, defining best enzyme concentration and reaction temperature. The best condition obtained (50 °C and 117 U g−1 of soybean fibre) was used to evaluate the co-production of xylooligosaccharides by the addition of different concentrations of arabinofuranosidase. The highest yield of xylooligosaccharides obtained was 28% (mass fraction of xylan), showing final concentrations (in mg g−1 arabino-xylan) of 138.36 xylobiose (X2), 96.96 xylotriose (X3), and 53.04 xylotetraose (X4), in 9 h enzymatic reactions. The conversion of arabino-xylans into different xylooligosaccharides suggests the potential to use recombinant A. nidulans A773 enzymes to obtain prebiotics using a sugar-rich, low-cost soybean residue.