Genomic and transcriptomic analysis of Candida intermedia reveals genes for utilization of biotechnologically important carbon sources

A future biobased society relies on efficient industrial microorganisms that can convert all sugars from agricultural, forestry and industrial waste streams into fuels, chemicals and materials. To be able to tailor-make such potent cell factories, we need a far better understanding of the proteins responsible for the assimilation of biotechnologically important carbon sources including pentoses, disaccharides and oligomers. The yeast Candida intermedia, known for its superior growth on xylose owing to its efficient uptake and conversion systems, can also utilize a range of other important carbon sources such as cellobiose, galactose and lactose.The aim of this project was to identify the genomic determinants for the utilization of these mono- and disaccharides in our in-house isolated C. intermedia strain CBS 141442.Genome sequencing and transcriptional (RNA seq) data analysis during growth in defined medium supplemented with glucose, xylose, galactose, lactose or cellobiose, revealed numerous distinct clusters of coregulated genes. By scanning the CBS 141442 genome for genes encoding Major Facilitator Superfamily(MFS) sugar transporters, and the RNA-seq dataset for the corresponding transcriptional profiles, we identified several novel genes encoding putative xylose transporters and multiple Lac12-like transporters likely involved in the uptake of disaccharides in C. intermedia. We also found that the yeast possesses no less than three genes encoding aldose reductases with different transcriptional profiles, and heterologous expression of the genes inSaccharomyces cerevisiae showed that the aldose reductases have different substrate and co-factor specificities, suggesting diverse physiological roles.Taken together, the results of this study provide insights into the mechanisms underlying carbohydrate metabolism in C. intermedia, and reveals several genes with potential future applications in cell factory development