Preheating Followed by Simultaneous Viscosity Reduction, Hydrolysis, and Fermentation: Simplifying the Process of Ethanol Production from Sweet Potato
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In traditional methods, the ethanol production from starchy raw materials includes the stages of viscosity reduction, full hydrolysis, and fermentation, which are carried out in two or more steps. We propose to perform all these steps together with the method called P-SVHF (preheating followed by simultaneous viscosity reduction, hydrolysis, and fermentation). The sweet potato starch was hydrolyzed by applying a commercial enzyme mixture specially developed to degrade granular starch. Nevertheless, when starch was previously gelatinized, the ethanol production was 52% higher than that in which starch was in the granular form. Thus, the proposed method (P-SVHF) also includes the starch gelatinization stage (preheating). In the P-SVHF method, energy is saved through (i) reducing the mass that is heated (only sweet potatoes), and (ii) applying a temperature (76 °C) which is lower than what is usually used during the liquefaction (≥ 85 °C), then an energy saving of 48% in comparison with traditional methods was estimated. After the method definition, a central composite design was carried out to evaluate the influence of pH, temperature, and time in the SVHF. The significant contributions of the optimization were the time reduction, i.e., from 24 h to 18–19 h, and the ethanol conversion efficiency increased to about 93%.
KeywordsSweet potato Starch Ethanol Fermentation Optimization
The authors would like to acknowledge the support from Coordination for the Improvement of Higher Education Personnel (CAPES) and the Federal University of Rio Grande do Sul (UFRGS); also, the authors would like to thank Tobias Romanzini Putti and Gabriela Baldin Susin for their collaboration in the experiment execution.
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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