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Mathematical modeling of second generation bioethanol production with cell recycle by using the microorganisms Scheffersomyces stipitis and Spathaspora passalidarum

Grant number: 16/14567-0
Support type:Scholarships in Brazil - Doctorate (Direct)
Effective date (Start): December 01, 2016
Effective date (End): January 31, 2020
Field of knowledge:Engineering - Chemical Engineering
Principal Investigator:Aline Carvalho da Costa
Grantee:Luiz Eduardo Biazi
Home Institution: Faculdade de Engenharia Química (FEQ). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
Associated scholarship(s):17/21634-9 - 13C-Metabolic flux analysis of fermentation in a Xylose/Glucose mixture substrate by yeasts Scheffersomyces stipitis NRRL Y-7124 and Spathaspora passalidarum NRRL Y-27907, BE.EP.DD

Abstract

Sugarcane bagasse is a lignocellulosic byproduct obtained from ethanol production (1G) and it's a promising substrate for second generation bioethanol production (2G). As hemicelluloses represents about 30% of bagasse dry weight, the amount of sugars generated after the hydrolysis of this material represents a substantial portion for the second generation bioethanol production. The yeast Saccharomyces cerevisiae is still the most used microorganism for ethanol production. However, the hydrolysis of cellulose and hemicelluloses results in a mixture of glucose, xylose, arabinose and other monosaccharides. This becomes a problem once S. cerevisiae, which can ferment hexoses derivated from the glucan portion of lignocellulose, is not capable to metabolize pentoses (xylose), unless it's genetically modified to express the pathways for xylose assimilation. Therefore, the transformation of pentoses in bioethanol becomes one of the most important challenges to be solved on scientific and technologic scope considering the production of bioethanol from biomasses.In this context, yeasts that are naturally capable of fermenting pentoses are highlighted, as Scheffersomyces stipitis and Spathaspora passalidarum, which are considered promising yeasts for industrial application in the bioethanol production from hydrolysates that are rich in pentoses due to their conversion metabolism of xylose to bioethanol. Differently of the yeast S. stipitis, which requires condition of microaerophilia to optimize the ethanol production, S. passalidarum is capable to produce ethanol in strictly anaerobic conditions, which becomes a differential characteristic in the choice of the microorganism. Considering the fermentation process, temperature has an important influence. In the case of the two microorganisms under study, there is still no certainty about the best operation temperature. Thus, a study of the fermentative process kinetic in function of temperature using a mixture of glucose and xylose as substrate is essential to define the optimal temperatures of growth and uptake of the different substrates, which makes it possible to propose different ways to optimize the process. Therefore, the central goal of the project is to determine the best yeast, among those studied in this proposal, as well as determine the fermentation kinetic in function of temperature for the second generation ethanol production using a substrate composed by glucose and xylose, and also to define the requirement or not of operating in microaerophilia condition. In addition, RNA sequencing will be performed for both S. stipitis and S. passalidarum in cell recycle batch fermentation, and the results of the expression of enzymes involved throughout the fermentation cycle will serve as framework for the use of this technology in the second generation bioethanol production. (AU)