USE OF COMPOSITE AGRO-SUBSTRATES FOR AMYLOGLUCOSIDASE SYNTHESIS AND CHARACTERIZATION BY Aspergillus niger OTF AND Aspergillus flavus CLOR1 USING SOLID STATE FERMENTATION

Abstract

Amyloglucosidase catalyses the hydrolysisof glycosidic residues from non-reducing ends of amylose and amylopectin in starch components to produce β-D-glucose for industrial processes. The utilization of composite agro-substrates for amyloglucosidase production byAspergillus niger OTF and A. flavus CLOR1 using solid state fermentation and characterization of the enzyme were investigated. The substrates include rice bran (R), soybeans flour (S), palm kernel cake (P), wheat bran (W) and oyster shell (O) at various compositions (Medium I – VIII) were supplied with adequate moisture content for a solid culture medium of fermentation.They were inoculated into with the isolates and incubated at 30 °C for 120 h respectively. Cultural conditions such as temperature, pH and storage stability were optimized. Medium I (WSPO; 100:2:3:1, w/w) yielded amyloglucosidase activity 83.92 Ug-1and Medium V (WSP; 100:2:3, w/w) resulted into activity 67.64 Ug-1 at 48 h optimal time. There was decline in activity after 48 h in all samples but with maximum activity at pH 5. Aspergillus niger OTF showed maximum amyloglucosidase activity23.5 Ug-1 as compared with A. flavus CLOR1 20.07 Ug-1 at 30 ºC. The residual activities in term of storage stability were 43.9% and 44.9% at 4 °C and 68. 6% and 27.8% at 28 °C at week 2 respectively which later declined over a period of time. This study revealed that higher glucoamylase activity was significantly enhanced using these inexpensive and readily available agro-residues by both strains of isolates in solid culture medium. Thus, these residues could be a potential and economic source for the production of amyloglucosidase.