Obtaining a fluorescent and resistant hybrid yeast to the nystatin / Obtenção de levedura híbrida fluorescente e resistente a nistatina

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Vats contamination by wild yeasts can harm the efficiency and the productivity of ethanol industrial production and there are not efficient methods to control this type of contamination. Easiness, speed and the low cost would be desirable characteristics for the control of yeasts that eventually contaminate the fermentation process. With this aim, TAVARES (1989) developed an ethanol production process with the control of spoilage yeasts contaminants, that uses a Saccharomyces cerevisiae hybrid M606, of high productivity and resistant to the nystatin. It´s a wide spectrum antifungal that can be used to guarantee the genetic purity of the industrial inoculum. To facilitate the yeasts identification, GOMES et al. (2000) used the fluorescence property expressed by the GFP gene "Green Fluorescent Protein", that is controlled by the promoter of ADH2 in a low glucose concentrations. The association of these two properties in an industrial yeast strain would allow to maintain the purity of the inoculum and it would facilitate its identification. With this aim, an assay of genetic transformation of hybrid M606 with pYGFP3 plasmid built by Gomes et al (2000) was made, but it had not success. Therefore, as initial step for obtaining of both properties in hybrid highly productive, It was opted for the methodology of crossings between a nystatin resistant haploid segregant strain M606-2c(n) and the strain X2904-GFP3(n) harboring of the plasmid pYGFP3. Some hybrids were selected of this natural crossing, with subsequent evaluation of nystatin resistance level, stability of the pYGFP3 plasmid and fermentative capacity. The selected hybrids (P16, P34 and P42) were capable to grow in a concentration of 10mg.nystatin L-1. However, plasmidial instability of the pYGFP3 was detected in all the selected hybrids. The hybrids P34 and P42 showed a smaller fermentative capacity than control strain, which can be explained by the fragility of the membranes system due to the nature of the resistance to the nystatin. The hybrid P16 did not showed difference in the fermentative capacity to the strain control. In spite of obtaining resistant hybrid to the nystatin expressing the GFP3 gene, there is a need to modify the pYGFP3 plasmid, turning it integrative in the yeast genome to allow the gene stability GFP3.

ASSUNTO(S)

antifúngicos cana-de-açúcar saccharomyces melhoramento genético fermentation leveduras genetic transformation fermentação alcoólica

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