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).

Keywords:

• enzyme activity
• phenylalanine ammonia lyase
• batch and fed-batch processing
• optimization
• Rhodotorula mucilaginosa