Co-overexpression of Genes RFE1, GND1, and RIB6 Enhances Riboflavin Production in Yeast Candida famata

Riboflavin (vitamin B2) is an essential compound for the nutrition of living organisms, serving as a precursor of coenzymes flavin mononucleotide and flavin adenine dinucleotide, which are involved in numerous enzymatic reactions mainly in oxidative metabolism. The yeast Candida famata is a natural riboflavin-producing species, which are able to oversynthesis riboflavin under conditions of iron starvation. The aim of this study was to construct recombinant C. famata strains with increased riboflavin production by the simultaneous overexpression of the three genes: RFE1, GND1, and RIB6, which encode riboflavin excretase, 6-phosphogluconate dehydrogenase and 3,4-dihydroxy-2-butanone-4-phosphate synthase, respectively. The expression of various combinations of two genes, as well as the co-expression of all three genes, resulted in increased riboflavin production in C. famata VKM Y-9 in different media. The strains engineered for the co-overexpression of all three genes exhibited up to a 3.3-fold increase in riboflavin production by the fifth day of cultivation in cheese whey, compared to the parental strain.