Alcoholic fermentation of raw cassava starch by Rhizopus koji without cooking

Abstract

Using only wheat bran koji from the Rhizopus strain, raw cassava starch and cassava pellets converted reasonably well to alcohol (ethanol) without cooking at 35 degrees C and pH 4.5-5.0. When the initial broth contained 30 g raw cassava starch, 10 g Rhizopus sp. koji, and 100 mL tap water, 12.1 g of alcohol was recovered by final distillation from fermented broth. In this case, 12.1 g alcohol corresponds to an 85.5% conversion rate based on the theoretical values of the starch content. When the initial broth contained 40 g cassava starch, 14.1 g of alcohol was recovered, where 14.1 g corresponds to a 74.5% conversion rate. The alcoholic fermentation process described in the present work is considered more effective and reasonable than the process using raw starch without cooking reported until now, since the new process makes it unnecessary to add yeast cells and glucoamylase preparation.