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Microbial oil production by adapted strains of oleaginous yeasts from hemicellulosic hydrolysates aiming at their application in biorefineries

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Author(s):
Nemailla Bonturi
Total Authors: 1
Document type: Doctoral Thesis
Institution: Universidade Estadual de Campinas, Faculdade de Engenharia Química
Defense date:
Advisor: Everson Alves Miranda
Abstract

Hemicellulosic hydrolysates such as those from sugarcane bagasse (HBCA) and birch woodchips (HEHB) are low cost substrates for single cell oil (SCO) production. However, these hydrolysates have low carbon/nitrogen (C/N) ratios and contain microbial growth inhibitors. Yeast adaptation, detoxification or fed-batch cultivation are strategies for overcoming the presence of these inhibitors and concentration or the addition of crude glycerol (a residue of biodiesel production) are alternatives to solve the low C/N ratio limitation. This work aimed at the adaptation of oleaginous yeasts Rhodosporidium toruloides and Lipomyces starkeyi for their use in SCO production using hemicellulose hydrolysates overcoming the low C/N ratio and inhibitors effects. R. toruloides and L. starkeyi adaptions were done in HBCA and in HEHB, respectively. The adapted strain of L. starkeyi was cultured in HEHB but low lipid concentration (1.8 g/L) was obtained and the studies were continued only with adapted R. toruloides. This strain of R. toruloides produced 225% more lipids in a mixture of xylose and glucose than the parental one. Also, the adapted strain overexpressed some genes of the pentose phosphate pathway and some genes specifically related to lipid accumulation. Concentration of the HBCA or the addition of glycerol were responsible for increasing the lipid content, concentration, and productivity in at least 108%, 175%, and 118%, respectively, compared to fermentation using only HBCA. Further experiments on bioreactors increased lipid content and productivity by 33% and 54%, respectively. From the data aforementioned, it can be concluded that adaptation resulted in a R. toruloides strain with superior trait for lipid production in hydrolysates that overexpress key genes related to lipid accumulation. Hydrolysate concentration or glycerol addition are simple and easy strategies to be applied that can increase considerably SCO production in hydrolysates. The production of lipids in non-detoxified concentrated hydrolysate by the yeast R. toruloides is not yet reported in the literature (AU)

FAPESP's process: 13/03103-5 - Integrate study of the single cell oil production by non-conventional yeasts utilizing hemicellulosic hydrolysate with cell harvesting by flotation aiming their application in biorefinery
Grantee:Everson Alves Miranda
Support type: Regular Research Grants