Exploring the potential of biodiesel derived crude glycerol into high value malic acid: Biosynthesis,process optimization and kinetic assessment

In this study, Zygosaccharomyces rouxii, a sugar tolerant yeast culture was explored for the production of high value malic acid using crude glycerol from biodiesel plant. In addition, the effect of addition of glutamic acid (precursor) (0.25 to 1%), temperature (15 to 30 ​°C) and time (0 to 24 days) of the fermentation process was also investigated by both conventional as well as Response Surface Methodology (RSM). The highest malic acid of 72.1 ​± ​0.05 ​g/L was obtained and RSM predicts the accurate optimized conditions such as 30% crude glycerol concentration in the fermentative media with 0.75% addition of precursor with initial pH 5 ​at 20 ​°C for 20 days. This study reveals that the crude glycerol can be efficiently used and the production of malic acid was raised with 3 folds correspond to no precursor under optimal conditions. The growth and product kinetics were studied by Monod, Logistic, Leudeking Piret as well as Logistic incorporated Leudeking-Piret models with and without precursor and Logistic incorporated Leudeking-Piret model allowed the best fit for the malic acid production.