Optimization of gamma-decalactone production by Yarrowia lipolytica mutant strain via Response surface methodology

Nowadays, aromatic componds are widely used in food, pharmaceutical, cosmetic and chemical industries. Due to the growing tendency of consumers to use natural products, biotransformation by microorganisms is an interesting method for the production of aromatic compounds. Gamma-decalactone is a cyclic aroma with a peach-like flavor. The non-conventional yeast Yarrowia lipolytica can bioconversion the inexpensive castor oil substrate into the valuable gamma-decalactone. The process begins with the hydrolysis of castor oil by the lipase to ricinoleic acid, then continues by shortening the chain by beta-oxidation, and finally ends by lactonization. In this study, gamma-decalactone production was optimized via Response surface methodology (RSM) by a mutant strain of this yeast with the ability to produce high amounts of lipase. For this purpose, castor oil, yeast extract, peptone and pH were studied as factors at five levels. Based on statistical analysis of the relationships between the experimental variables, a mathematical model was obtained for the governing relationships between the experimental variables. Based on the results, the best values were obtained for castor oil 35 ml/l, yeast extract 6 g/l, peptone 8.5 g/l and pH 4. To validate the mathematical model, the proposed values were tested and 126 mg/L of gamma-decalactone was produced by the yeast strain, which shows a 46% increase compared to non-optimal conditions. The results of this study can be used to make cost-effective production of gamma-decalactone from castor oil by microbial biotransformation process.