Antagonismo entre leveduras e bactérias láticas na fermentação alcoólica / Antagonism between yeasts and lactic acid bacteria in alcoholic fermentation

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

This study aimed to evaluate the antagonism between yeasts and contaminating bacteria of the ethanol production process with different metabolisms (homo- and heterofermentative) in different conditions. Thus, the fermentation performance of Saccharomyces cerevisiae strains used in industrial fermentation (BG-1, CAT-1, PE-2 and Fleischmann) was analyzed in co-cultivation with Lactobacillus strains with different metabolisms, one of them homofermentative (L . plantarum - FT025B) and two heterofermentatives strains (L. fermentum - FT230B and L. fructosus - FT432B). It was evaluated the growth of two microrganisms groups with respect to the cells density in the medium and their viability and also through their metabolic activities, accessed by specific metabolites production (lactic, acetic and succinic acid, mannitol and ethanol). The experiments were conducted in two ways: I) in laboratory conditions, inoculating a bacterial strain with a single yeast strain in the same synthetic medium incubated at 32°C for 24h and II) simulating the industrial fermentation conditions, with fed by using mixed must for 5 fermentative recycle. In Experiment I, the viability of FT025B strain proved to be small in relation to FT230 strain. It was also observed that in the medium containing the bacteria FT025B the viability of the 4 yeast strains was lower than the control and the treatment with FT230B strain. The levels of lactic acid were higher in the presence of bacteria FT025B, while the levels of acetic acid and glycerol were higher in treatments with FT230B strain. The production of ethanol was reduced in the presence of both bacteria. In Experiment II, the presence of bacteria did not affect the viability of industrial yeasts during recycling. However, contrary to what was observed in Experiment I, the heterofermentatives bacterial strains showed higher growth and higher viability in co-cultivation with the yeasts than homofermentative. Also in the presence of both strains heterofermentatives there was a significant reduction in the alcoholic yield. The lactate production by these strains was very close and, in some cycles, higher than the production by the homofermentative strain. However, as in Experiment I,in the treatments with FT025B strain the production of glycerol was lower even than in the control treatment, this is the first record of lower production of glycerol by yeasts that are in the presence of bacterial contamination. It is suggested that the lactic acid and acetic acid along with ethanol, may have acted synergistically in yeasts metabolism and growth, resulting in reduced alcoholic yields. It is also likely that the bacterial strains heterofermentatives were better able to resist the high ethanol levels excreted by yeasts and found in industrial process, since they are also able to produce this compound.

ASSUNTO(S)

lactobacillus lactic acid bacteria - contamination antagonists fermentação alcoólica antagonistas yeasts. alcoholic fermentation leveduras. bactérias láticas - contaminação etanol ethanol lactobacillus

ACESSO AO ARTIGO

Documentos Relacionados