Abstract
The ascomycetous yeast Candida membranifaciens has been isolated from diverse habitats, including humans, insects, and environmental sources, exhibiting a remarkable ability to use different carbon sources that include pentoses, melibiose, and inulin. In this study, we isolated four C. membranifaciens strains from soil and investigated their potential to overproduce riboflavin. C. membranifaciens IST 626 was found to produce the highest concentrations of riboflavin. The volumetric production of this vitamin was higher when C. membranifaciens IST 626 cells were cultured in a commercial medium without iron and when xylose was the available carbon source compared to the same basal medium with glucose. Supplementation of the growth medium with 2 g/L glycine favored the metabolization of xylose, leading to biomass increase and consequent enhancement of riboflavin volumetric production that reached 120 mg/L after 216 h of cultivation. To gain new insights into the molecular basis of riboflavin production and carbon source utilization in this species, the first annotated genome sequence of C. membranifaciens is reported in this article, as well as the result of a comparative genomic analysis with other relevant yeast species. A total of 5619 genes were predicted to be present in C. membranifaciens IST 626 genome sequence (11.5 Mbp). Among them are genes involved in riboflavin biosynthesis, iron homeostasis, and sugar uptake and metabolism. This work put forward C. membranifaciens IST 626 as a riboflavin overproducer and provides valuable molecular data for future development of superior producing strains capable of using the wide range of carbon sources, which is a characteristic trait of the species.
Highlights
IntroductionCandida membranifaciens is an anamorphic yeast first described as Candida melibiosi var
Valuable information regarding the isolation of C. membranifaciens strains from soil samples and the general ability of the species to produce riboflavin that, to date, was considered exclusive of C. membranifaciens subsp. flavinogenie W14-3 was provided
Among the C. membranifaciens isolates obtained and tested, strain C. membranifaciens IST 626 was selected as the best riboflavin producer and demonstrated that riboflavin production can be improved by culture medium optimization
Summary
Candida membranifaciens is an anamorphic yeast first described as Candida melibiosi var. Membranifaciens by Lodder & Kreger-van Rij [1]. Based on the examination of strains assigned to Candida melibiosi var. Melibiosi, and C. guilliermondii, Wickerham and Burton observed that the variety membranifaciens was unable to mate and able to ferment melibiose more vigorously than C. melibiosi [2]. Membranifaciens was proposed as the new species C. membranifaciens. Upon phylogenetic analysis of the D1/D2 domains of the large subunit and the nearly complete small subunit rRNA genes from species that express the coenzyme Q-9 form, C. membranifaciens was phylogenetically placed in the Yamadazyma clade of Debaryomycetaceae family [3]
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