Roles of Process Parameters on the Ricinoleic Acid Production from Castor Oil by Aspergillus flavus BU22S

Abstract

Ricinoleic acid is a biobased green chemical industrially produced from castor oil. Microbial conversion is a cleaner and greener approach to ricinoleic acid production from castor oil. These processes should be further optimized for a better yield of the product. Aspergillus flavus BU22S was used to convert castor oil into ricinoleic acid. The strain was isolated and identified by molecular biological techniques. It was found to be effective in the biotransformation of castor oil. The ricinoleic acid production and dry cell weight of the fungus were studied as functions of time. In this study, to increase the yield of ricinoleic acid and decrease the oil loss, which microorganisms utilizes in biomass production, response surface methodology (RSM) has been used for process optimization. The central composite design was used to optimize the predictor variables such as oil concentration (% w/v), glucose concentration (% w/v), and calcium chloride concentration (% w/v) to increase the overall yield of ricinoleic acid. A quadratic model was found to be the best fit to predict the responses of the experimental results. The model suggested that the concentrations of oil, glucose, and calcium chloride should be lower in order to increase the ricinoleic acid yield and minimize the oil loss. The bench scale studies of optimized conditions from RSM were also conducted. The yield of ricinoleic acid in batch and fed-batch culture studies was also compared. The yield of the ricinoleic acid in batch culture was 21.67 g/kg of total oil. The yield of ricinoleic acid in fed-batch culture in the absence of an external air supply was 46.77 g/kg of total oil. In this case, the oil loss was also reduced to only 12%.