Ethanol production from Oxalis tuberosa starch: study of enzymatic hydrolysis and alcoholic fermentation (#1593)

Authors

Rafael-Ayala, Anshela

Vejarano, Ricardo

Abstract

Andean tubers are an important source of starch. Although potatoes, sweet potatoes or cassava are the best known, there are other underutilised tubers such as oca, olluco, arracacha, mashua, among others. The aim of the study was to evaluate the potential use of oca starch (Oxalis tuberosa) to obtain ethanol, studying the optimal conditions of enzymatic hydrolysis of starch and subsequent alcoholic fermentation. An initial screening using a Plackett-Burman design to identify the independent variables with the highest impact on the hydrolytic process was applied. Subsequently, the identified variables were used in a Rotational Central Composite Design (CRDC) to determine the optimal values of these variables in the hydrolytic process. Among the main results, the concentration of the enzymes had a significant impact on the hydrolytic process, achieving a conversion of up to 93% in the starch hydrolysis to dextrins (liquefaction) at an optimal α-amylase concentration of 0.41%, as well as the subsequent hydrolysis of those dextrins into fermentable sugars (saccharification) at rates greater than 93% at an optimal glucoamylase concentration of 0.75%. In the alcoholic fermentation stage, a Conversion Efficiency of fermentable sugars into ethanol of 89% was obtained using yeast extract as N-source for the yeast Saccharomyces cerevisiae. Based on the results, for every 1000 kg of oca, up to 30 L of ethanol could be produced, which can later be used for different purposes such as the production of alcoholic beverages, biofuel, medicinal use, among other applications.