Genes Family and Transcription Factor Regulate Biofilm Formation During Immobilized Fermentation.

immobilization is commonly used for efficient ethanol fuel production in industry due to the relatively higher ethanol stress resistance of in biofilms relative to planktonic cells. The mechanisms of biofilm formation and stress resistance, however, remain ambiguous. By analyzing biofilm and planktonic cell transcriptomes, this study observed that (encoding a transcription factor) expression in cells increases during the biofilm formation process. To identify the role of in yeast biofilm formation and the ethanol resistance of these cells, was deleted and complemented in 1308. Results showed the deletion mutant strain demonstrated weaker biofilm formation ability both on fibers and plastic than the wild-type and these could be restored by expressing in deletion mutant. To verify the ability of to regulate the expression of genes, which encode adhesions responsible for yeast biofilm formation, gene transcription levels were measured via qRT-PCR. Relative to wild-type , the adhesion genes , and which also demonstrate increased expression in the transcriptome of yeast cells during biofilm formation, but not , were down-regulated in the mutant strain. Additionally, the mutant lost a majority of its flocculation ability, which depended on cell-cell adhesions and its slightly invasive growth ability, dependent on cell-substrate adhesion. Deleting , and decreased biofilm formation on plastics, suggesting these genes contribute to the biofilm formation process alongside . Moreover, the ethanol tolerance of yeast decreased in the deletion mutant as well as the deletion mutant, resulting in reduced biofilm formation during fermentation. It remains possible that in the later period of fermentation, when ethanol has accumulated, an over-expression of the , and genes regulated by would enhanced cell-cell adhesions and thus protect cells in the outer layer of biofilms from ethanol, a function primarily dependent on cell-cell adhesions. This work offers a possible explanation for how biofilm formation is regulated during the immobilized fermentation process, and can enhance environmental tolerance in industrial production.