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Fed-batch ethanol fermentation at low temperature as a way to obtain highly concentrated alcoholic wines: Modeling and optimization

Author:
Veloso, Ivan I.K., Rodrigues, Kaio C.S., Sonego, Jorge L.S., Cruz, Antonio J.G., Badino, Alberto C.
Source:
Biochemical engineering journal 2019 v.141 pp. 60-70
ISSN:
1369-703X
Subject:
batch fermentation, cell viability, ethanol, ethanol fermentation, ethanol production, kinetics, models, temperature, wines, yeasts
Abstract:
The effect of product inhibition on yeast hinders the production of wine with ethanol concentration above 80.0 g L−1 (∼10°GL) in the industrial ethanol production process commonly performed at 34 °C. Lowering the fermentation temperature is a way to produce wines with higher ethanol contents. In this work, batch fermentations were carried out at temperatures of 28, 30, 32, and 34 °C, with initial substrate concentration of 180.0 g L−1, using industrial yeast under conditions reproducing those found in industry. The Andrews-Levenspiel hybrid kinetic model, considering viable cells, showed an excellent fit to the experimental data. Kinetic parameters were determined for the different temperatures. The model was used to simulate fed-batch fermentations at different temperatures, with the same total substrate concentration, resulting in satisfactory descriptions of the process behaviors. A new optimization strategy to obtain the maximum possible ethanol production, based on the CEmax parameter of the Andrews-Levenspiel kinetic model, provided ethanol production of up to 134.7 g L-1 (17.1°GL) at 28 °C and 305.4 g L−1 substrate. A modification was made to the Andrews-Levenspiel kinetic model, relating the n parameter to the final ethanol concentration (CEf), in order to enable the model to describe the behavior of fed-batch fermentations performed with high substrate concentration and at temperatures from 28 to 34 °C.