Enhancement of phenylalanine ammonia lyase production from Rhodotorula mucilaginosa by optimization of culture conditions in batch and fed-batch

Abstract

The fermentation of phenylalanine ammonia lyase (PAL) by Rhodotorula mucilaginosa (R. mucilaginosa) was optimized. PAL production was enhanced 8.0-fold from an initial activity of 5 U/g (DCW) with the incorporation of optimization of medium composition, controlled-pH operation, the strategy of batch supplementation with substrate induction and other culture conditions, and the implementation of a fed-batch process. A significant influence of peptone and inoculum size on PAL production was evaluated by Plackett-Burman design and the path of steepest ascent experiment. Among the various amino acids used, it was found that L-Phenylalanine could efficiently induce the biosynthesis of PAL. PAL activity was increased by 18.5 % in comparison with the control. Glucose concentration significantly affected PAL synthesis. When the glucose concentration was 1 g/L, PAL activity was enhanced by 1.82- and 6-fold in comparison with those at 5 g/L and 10 g/L, respectively. To further increase PAL production, controlled-pH operation and the strategy of batch supplementation with the inducer was performed in a 5 L stirred tank reactor. The maximum production of PAL reached 41 U/g (DCW).