Tsyrulnyk A. New factors involved in the regulation of flavin synthesis in the yeast Candida famata

In the work, yeast homologue (RFE1_Dh) of the human RF-excretase gene (BCRP1) was introduced to the previously constructed RF overproducer of the yeast Candida famata. The introduction of the RFE1_Dh gene led to a 1.5-fold increase in RF production by BRP/RFE1 recombinants compared to the recipient strain BRP, as well as to a decrease in the content of intracellular flavins. The obtained results indicate that by increasing the RF excretion, it is possible to increase the level of its production. Overexpression of the gene of transcription factor Sef1 under the control of the LAC4 promoter ensured a 1,5-fold increase in RF production using cheese whey as a nutrient medium. Analysis of the flavinogenic activity of RF-overproducing yeast strains AF-4, BRP, BRPI, BRP/RFE1, BRP/RFE1/prLAC4-SEF1 and BRPI/prLAC4-SEF1 also revealed the ability to synthesize this flavin at a high level in whey. It was established that active growth and flavinogenesis of yeast in cheese whey is possible only when an additional source of nitrogen is added in the form of urea, ammonium sulfate or diammonium hydrophosphate at a low content of lactose (2-5%). Using of cheese whey as a nutrient medium for microbial synthesis of RF will significantly reduce the cost of RF production. The final part of the work was the construction of the yeast producer of the bacterial antibiotic compound - aminoriboflavin (AF). Synthetic rosB gene S. davaonensis with modifications of the codon system was introduced into the FMN-overproducer FP C. famata strain. The results of chromatographic and mass-spectrometric analyzes confirmed that obtained recombinant strains FP/RosB C. famata are able to produce the AF up to 5 mg/L.