Abstract
Bioethanol is a renewable fuel as an alternative source of energy of worldwide importance. The present study aimed to evaluate alcohol production from sweet potato, under varying reaction conditions for fermentation and hydrolysis. A genotype was selected to obtain dried flour and processed by acid hydrolysis and enzymatic hydrolysis with α-amilase and amiloglucosidase. The experiment was carried out in a completely randomized block design with three central point replicates combined with response surface methodology. The variables were pH, temperature and fermentation time. The alcohol content was determined by distillation with subsequent spectrophotometric analysis. Raw materials were characterized according to moisture, reducing sugars and starch, and 4.13%, 4.04% and 71.80% were obtained, respectively. Acid hydrolysis showed higher alcohol percentages of distilled samples. The highest values for acid hydrolysis and enzymatic hydrolysis in fermentations were 26.42% and 25.04%, respectively, carried out at pH 5.0 and 36°C for 5 days. The fermentation time was the most important variable, with higher and significant values for both types of hydrolysis. Acid hydrolysis presented higher potential for alcoholic production than enzymatic hydrolysis in sweet potato fermentation.
Highlights
Alcohol can be produced from different types of vegetable raw material sources
Tian et al (2018) evaluating 12 genotypes of sweet potato tubers with different storage times, observed that the starch content was weakly correlated with other ingredients, while the percent dry content and fermentable sugars contents had a close correlation with starch content of the flour and there were significant differences in the bioethanol production with the same storage time and different sweet potato genotype
The results indicate that acid hydrolysis is more efficient for obtaining alcohol from sweet potato
Summary
Alcohol can be produced from different types of vegetable raw material sources. These renewable energy sources may have considerable amounts of fermentable carbohydrates. They are classified into three specific groups: sugary, starchy and cellulosic materials (Canilha et al, 2012). Sweet potato (Ipomoea batatas L.) is the sixth most cultivated food crop in the world after rice, wheat, potatoes, maize and cassava. The world production was 112.84 million ton of sweet potato. The China ranked in first with 72.03 million ton and 58.6% of the world production and Brazil with 0.77 million ton and approximately 0.6% of world production (FAO, 2017)
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