Aims: Fermentation and recovery are the major operating cost in biosurfactant production. Thus, the aim of this research was to synthesize biosurfactant from agricultural residues using suitable fermentation and recovery techniques in order to reduce the cost of production. Methodology and results: Biosurfactant-producing yeast strains isolated from refined oil-contaminated soil samples using yeast extract-diesel agar (YEDA) were subjected to physicochemical screening such as drop collapse test, microplate analysis, oil spreading technique, emulsification index and thermostability. Based on the preliminary screening result, Candida lusitaniae P1, C. parapsilosis P51, C. parapsilosis D3 and C. lusitaniae E1 were selected for biosurfactant production using agricultural residue such as rice bran, wheat bran and coconut shell as substrate and crude supernatant was analyzed by gas chromatography mass spectrometry. Candida lusitaniae P1 strain produced 98.96 g/L of biosurfactant from coconut shell but when subjected to mutagenesis the yield decreased to 52.24 g/L. Conclusion, significance, and impact of study: The physicochemical properties of biosurfactant produced using various carbon sources showed that coconut-shell is the best residue thus, variation in composition and concentration of biosurfactant obtained implies that the quality and quantity of biosurfactant produced depends on the carbon source and the genetic composition of the yeast isolate.
Candida ; Fermentation

Aims: Evaluation of enzymes responsible for microbial transformation of Curcuma longa to vanillin and quantification of phenolic compounds present during the process. Methodology and results: Yeast strains isolated from fermented beverages using curcumin-yeast extract agar were screened for their ability to transform curcumin to vanillin by evaluating ferulic acid esterase, ferulic acid decarboxylase, and vanillin dehydrogenase activities in growing cultures and cell-free supernatant. Based on bioconversion and enzymatic capabilities of the yeasts, Pichia angusta BT21 was selected for microbial transformation of Curcuma longa to vanillin using submerged fermentation technique under stationary mode. The metabolites were extracted from the transformation medium using solid-phase extraction technique and analyzed by thin-layer chromatography and gas chromatography-flame ionization detector. Phenolic compounds obtained in this research comprised of flavonoids (flavanols, flavones, isoflavones and flavonones), phenolic aldehyde (vanillin, vanillic acid, isoeugenol), simple phenolic (phenol) and phenolic acids (the hydroxybenzoic and the hydroxycinnamic acids) respectively. The research is quite profitable from an industrial point of view, considering the commercial price of vanillin and low cost and availability of C. longa which will eventually reduce the cost of industrial production of vanillin and increase supply. Conclusion, significance and impact of study: Bioprocessing of C. longa by submerged fermentation technique under stationary mode reduces vanillin dehydrogenase activity of the Pichia angusta BT21, thus preventing the degradation of vanillin which subsequently leads to increase in vanillin concentration.