Enzymatic hydrolysis of cassava starch for production of bioethanol with a colombian wild yeast strain

Abstract

Enzymatic hydrolysis of cassava starch for producing glucose syrups was evaluated using alpha-amylase from Bacillus licheniformis and glucoamylase from Aspergillus niger. Moreover, an enzyme mixture of α-amylase from Aspergillus kawachi and glucoamylase from Aspergillus niger was tested. Enzyme conditions for starch hydrolysis were optimized by a factorial experimental design (33×2) using as variables substrate concentration, enzyme/substrate ratio and time reaction. Optimal enzyme reactions with 100 g of starch per L were: a-amylase at pH 5.0, 80°C and enzyme dosage of 130.5 U g-1 of starch; and glucoamylase, pH 4.5, 70°C and enzyme dosage of 81.5 U g-1 of starch. Additionally, optimal conditions for the enzymatic mixture were pH 4.5, 46°C, and enzyme dosage of 16.4 U g -1 of starch. Finally, alcohol production using glucose syrups from enzymatically-hydrolyzed starch was carried out with a wild strain of Candida sp isolated from sugar cane juice, obtaining volumetric ethanol productivities around 1.8-3.2 g L-1h-1. © 2011 Sociedade Brasileira de Química.