Secretome produced by a newly isolated Aspergillus flavus strain in engineered medium shows synergy for biomass saccharification with a commercial cellulase

Abstract

In this study, we evaluated the saccharification potential of the secretome produced by a new elephant faeces isolate Aspergillus flavus (AF-NGF1), alone as well as in combination with a commercial enzyme (CTec2). Medium engineering (involving sequential Taguchi design, response surface methodology and one factor at a time approaches) enhanced the cellulase (FPase) secretion in the secretome of isolate AF-NGF1 (AF-S) by 3.89-folds. AF-S showed a maximum increase of 7.1- and 8.69-folds in exo-glucanase (avicellase) and endo-glucanase (CMCase) activities, respectively. Equal enzyme loading (20 FPU/g of biomass) of AF-S and CTec2 showed comparable saccharification potential with acid pre-treated paddy straw (APPS). However, a 1:1 combination of AF-S and CTec2 showed 67.84% and 37.21% increased saccharification of APPS as compared with AF-S or CTec2 alone at 50 °C and 40 °C, respectively. During simultaneous saccharification and fermentation (SSF) at 40 °C, a 1:1 combination produced > 2-folds increased ethanol titre as compared with AF-S or CTec2 alone. When equal FPU of AF-S and CTec2 were mixed for a total of 20 FPU, the degree of synergy (DOS) for APPS saccharification was 1.79 ± 0.06 and ~ 30.49% increased FPase activity was detected, which suggested the synergistic correlation between AF-S and CTec2. Therefore, the combination of AF-S and CTec2 could be considered as a potential cellulolytic enzyme formulation for efficient biomass hydrolysis and SSF process for lignocellulosic ethanol production.