Discovery of citric acid producing yeasts to use in industry

Citric acid is one of the industrial products with extensive applications which are used in the food, pharmaceutical, cosmetics and chemical industries. Although to 1965 Aspergillus niger was single strain to production of citric acid but yeasts are good candidate for citric acid production because growth on cheap and disposal substrates such as hydrocarbon and oils, low sensitive to trace elements in raw material. In this study, citric acid producing yeasts were isolated. Among 340 isolated yeast strains from dairy, meat and food products from Isfahan factories on screening media. 12 strains cultivated in citric acid production medium have been chosen for further study. Production of citric acid was determined by colorimetric method and Megazyme kit during 192 hours. One of the isolated yeasts with 55.5 g/g citric acid production along 144 hours after inoculation had the best yield. Biochemical and molecular tests showed that this strain belonged to the species Yarrowia lipolytica, molecular tests confirmed by sequencing; therefore it was named as Y. lipolytica M7 with accession number HM011048 in Genbank.