Conversion of cassava starch to ethanol and a byproduct under different hydrolysis conditions

Abstract

Cassava starch can be converted into sugars by enzymatic hydrolysis to be used for ethanol production. In this work, the studied variables were starch and enzymes concentration seeking a higher conversion of the reducing sugars routine. Two series of experiments were conducted following the steps of gelatinization, liquefaction, and saccharification, ending with the fermentation step. It was found that a 100–250 times increase in α-amylase concentration results in a 23% increase in the starch yield. Therefore, an optimal enzyme concentration could be found. The glucoamylase enzyme has proved to be more effective, evaluated by the rate of starch conversion (k), at a lower concentration of starch (10%), and enzyme (10 U/g). In simultaneous saccharification and fermentation (SSF), the hydrolysis yield was 33% higher than in a conventional process, achieving efficiencies higher than 70%. The solid residue separated after the SSF process proved to be a high-quality animal feed additive.