Comprehensive studies on optimization of cellulase and xylanase production by a local indigenous fungus strain via solid state fermentation using oil palm frond as substrate.

The high cost of cellulases remains the most significant barrier to the economical production of bio-ethanol from lignocellulosic biomass. The goal of this study was to optimize cellulases and xylanase production by a local indigenous fungus strain (Aspergillus niger DWA8) using agricultural waste (oil palm frond [OPF]) as substrate. The enzyme production profile before optimization indicated that the highest carboxymethyl cellulose (CMCase), filter paper (FPase), and xylanase activities of 1.06 U/g, 2.55 U/g, and 2.93 U/g were obtained on day 5, day 4, and day 5 of fermentation, respectively. Response surface methodology was used to study the effects of several key process parameters in order to optimize cellulase production. Of the five physical and two chemical factors tested, only moisture content of 75% (w/w) and substrate amount of 2.5 g had statistically significant effect on enzymes production. Under optimized conditions of 2.5 g of substrate, 75% (w/w) moisture content, initial medium of pH 4.5, 1 × 106 spores/mL of inoculum, and incubation at ambient temperature (±30°C) without additional carbon and nitrogen, the highest CMCase, FPase, and xylanase activities obtained were 2.38 U/g, 2.47 U/g, and 5.23 U/g, respectively. Thus, the optimization process increased CMCase and xylanase production by 124.5 and 78.5%, respectively. Moreover, A. niger DWA8 produced reasonably good cellulase and xylanase titers using OPF as the substrate when compared with previous researcher finding. The enzymes produced by this process could be further use to hydrolyze biomass to generate reducing sugars, which are the feedstock for bioethanol production.

Enhancement of cellulolytic enzymes and xylanase production via classical mutational techniques under solid-state fermentation condition

Aims: High cost of cellulases remains the most significant barrier to the economical production of bio-ethanol from lignocellulosic biomass (LB). The present study aims at developing a local cellulolytic fungal strain through random mutagenesis coupled with the feasibility of solid-state fermentation (SSF) by utilizing agricultural wastes such as oil palm frond (OPF) as the substrate. Methodology and results: Out of 95 wild isolates tested, native fungal strain Aspergillus niger, designated DWA8 was isolated as the top enzymatic secretor. For quantitative enzyme analysis, SSF was conducted using 1x106 spore/mL inoculated onto 5 g of ground OPF, incubated at room temperature for 7 days, with 70% moisture content and an initial medium pH of 7. Random mutagenesis has always been tempting in the enhancement of enzyme production. In this work, the compounded treatment of microwave, ultraviolet (UVC) and Ethyl Methanesulfonate (EMS) have generated an Aspergillus niger MUE3.06 mutant with an overall increase of 114% in CMCase activity, approximately 70% in FPase and Xylanase activity respectively compared with the parental DWA8 strain. Thus this finding is capable to be fully developed as an established mutational scheme to create highly productive filamentous fungus in a cheap, simple and sustainable way. Conclusion, significance and impact of study: It was the first attempt to explore the combine effect of the three popular mutagens upon cellulases and xylanases. It is believed that more diversified of mutagen types induce more diversified mutation pattern (with instructive planning), which is very desirable in creating new enzymes with novel abilities.