Contemporaneous synthesis of multiple carbohydrate debranching enzymes from newly isolated Aspergillus fumigatus SKF-2 under solid state fermentation: A unique enzyme mixture for proficient saccharification of plant bioresources

Abstract

The agricultural residues are the most plentiful renewable bioresources in our earth as they enriched with a good amount of polysaccharides like cellulose, hemicellulose, pectin, and starch. A newly isolated soil fungus Aspergillus fumigatus SKF-2 produced a cocktail of carbohydrate debranching enzymes under solid-state fermentation (SSF) using a mixture of sugarcane bagasse, wheat bran and orange peel in equal amount as inducible substrates. During optimization of fermentation condition through one factor at a time approach and subsequently by response surface methodology cellulase [CMCase (1447.89 U/gds), FPase (1401.98 U/gds), β-glucosidase (1461.23 U/gds)], xylanase (1897.43 U/gds), pectinase (1456.95 U/gds) and amylase (1821.34 U/gds) were evolved in higher titer. Most of the enzymes were optimally active at pH 7.0, stable up to pH 7.0-9.0 and at 30°-40 °C. The molecular weight of the CMCase, amylase, xylanase, pectinase, and β-glucosidase was determined as 21, 32, 50, 60 and 70 KDa, respectively. The kinetic indices like Km and Vmax were also in favorable ranges. Chemical as well as FE-SEM-EDX, FTIR and XRD analysis of the SSF substrates revealed a considerable structural deformation occurred by the action of enzymes evolved in the course of fermentation. The produced enzymatic combination mixture may have considerable industrial potentialities for complete saccharification of plant polysaccharides containing bioresources.