Upstream regulatory regions controlling the expression of the Candida utilis maltase gene

• Cre-LoxP system in combination with zeocin was successfully applied in polyploid Candida utilis for gene disruption.
• The length of maltase promoter with full strength was determined.
• The strength of the promoter was evaluated.
• Inductor/repressor sugars were found.

Candida utilis represents a promising expression host, generating relatively high levels of recombinant proteins. The current study presents preliminary characterization of the upstream regulatory regions controlling the carbon source-dependent expression of the C. utilis maltase gene. Cellobiose and soluble starch were recognised as inducers of maltase promoter, besides maltose. We successfully applied the Cre-loxP system to acquire a null mutant strain with disrupted maltase gene and promoter in polyploid yeast C. utilis. Furthermore, the strength and minimal functional region of the promoter was evaluated by measuring β-galactosidase activity. Our results suggest, the qPCR was shown itself a very smart method for relatively easy characterization of the transformants and correlation of the expression levels with gene dosage.