Seleção e evolução dirigida de leveduras para a utilização nas indústrias do bioetanol e cervejeiras

Abstract

The fermented product industries have been demanding alternatives for increasing yields and reducing fermentation costs. Nowadays, the technique known as adaptive evolution becomes an excellent tool to develop different yeast phenotypes for fermentative processes. Our research group has been developing since 2009 a project focused on the isolation of yeasts obtained from Brazilian bioethanol industries, obtaining a strain collection that reaches 289 isolates. The challenge of this work is focused on the use of this collection to identify some strains with characteristics of interest in two industries: beer and bioethanol. With regard to beer production, we have been able to identify up to 64 yeasts with maltose growth potential, indicating a promising result for the evolution of these linages. The two strains, LGBA-287 and LGBA-288, with higher capacity of maltose were used in fermentation experiments and when compared to an industrial lineage they were similar in fermentative capacity. The analysis of the production route of 4-vinylguayacol (4-VG) given by the expression of the PAD1 and FDC1 genes and complemented with beer sensory evaluation allowed to demonstrate that there are possibilities to obtain beers with aromatic complexity using yeasts isolated from bioethanol. The development of these strains may have a direct application in fermentative processes aiming at a better quality of the product. In the case of bioethanol, an isolated thermotolerant lineage (LGBA-01) was tested; commercial yeast CAT-1; an evolved CAT-1 phenotype (CATEV, evolved under multi-stress conditions). (I) significant changes in the expression of genes such as: production of glycerol (GPD1 and GPD2) and ethanol (ADH1), and the production of glycerol (GPD1 and GPD2) ; (II) Signals of metabolic pathway by expression of genes such as GPD1, GPD2, ADH1, ALD4, ADR1, AGT1, MAL31, ACS2, SUC2 and SNF1. The expression of these genes revealed that CATEV presented trade-offs associated to the process of adaptive evolution in response to unfavorable conditions. In HPLC analysis, LGBA-01 and CATEV showed high capacity of ethanol production when fermented at high temperatures. Finally, our results could contribute to both industry and the scientific community.