Identification of genes whose expressions are enhanced or reduced in baker's yeast during fed-batch culture process using molasses medium by DNA microarray analysis

Genes whose expression levels are enhanced or reduced during the cultivation process that uses cane molasses in baker's yeast production were identified in this study. The results showed that baker's yeast grown in molasses medium had higher fermentation ability and stress tolerance compared with baker's yeast grown in synthetic medium. Molasses apparently provided not only sugar as a carbon source but also provided functional components that enhanced or reduced expression of genes involved in fermentation ability and stress tolerance. To identify the genes whose expression is enhanced or reduced during cultivation in molasses medium, DNA microarray analysis was then used to compare the gene expression profile of cells grown in molasses with that of cells grown in synthetic medium. To simulate the commercial baker's yeast production process, cells were cultivated using a fed-batch culture system. In molasses medium, genes involved in the synthesis or uptake of vitamins (e.g., biotin, pyridoxine and thiamine) showed enhanced expression, suggesting that vitamin concentrations in molasses medium were lower than those in synthetic medium. Genes involved in formate dehydrogenase and maltose assimilation showed enhanced expression in molasses medium. In contrast, genes involved in iron utilization (e.g., siderophore, iron transporter and ferroxidase) showed enhanced expression in synthetic medium, suggesting that iron starvation occurred. The genes involved in the metabolism of amino acids also showed enhanced expression in synthetic medium. This identification of genes provides information that will help improve the baker's yeast production process.