Enzymatic Hydrolysis of Cassava Starch for Production of Bioethanol with a Colombian Wild Yeast Strain

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 a-amylase from Aspergillus kawachi and glucoamylase from Aspergillus niger was tested. Enzyme conditions for starch hydrolysis were optimized by a factorial experimental design (3(3)x2) using as variables substrate concentration, enzyme/substrate ratio and time reaction. Optimal enzyme reactions with 100 g of starch per L were: alpha-amylase at pH 5.0, 80 degrees C and enzyme dosage of 130.5 U g(-1) of starch; and glucoamylase, pH 4.5, 70 degrees C and enzyme dosage of 81.5 U g(-1) of starch. Additionally, optimal conditions for the enzymatic mixture were pH 4.5, 46 degrees 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(-1)h(-1).