Statistical Optimization of Media Constituents for Enhanced Production of Aspartase from Aeromonas media NFB-5

Aspartase (L-aspartate ammonia-lyase; EC 4.3.1.1) catalyzes the reversible amination of fumaric acid to produce L-aspartic acid. L-aspartic acid is an essential ingredient of artificial sweetner aspartame widely used in nutraceuticals and pharmaceuticals. The optimum production of aspartase by Aeromonas media NFB-5 at shake-flask level has been investigated using response surface methodology (RSM). Six central composite rotatable design (CCRD) parameters with varying concentrations were explored to find the most suitable combination for optimal production of aspartase and biomass yield. Aspartase production was the desired response and biomass yield was considered as the second response. Six variables optimized were glycerol (0.04-0.66%, v/v), peptone (0.11-0.89%, w/v), yeast extract (0.11- 0.89%, w/v), sodium L-aspartate (0.09-0.71%, w/v), KH2PO4 (0.09-0.71%, w/v) and K2HPO4 (0.14-0.46%, w/v), while NaCl (0.2%, w/v), MgSO4 (0.01%, w/v) and pH (7.0±0.2) were kept constant during shake-flask fermentation. Optimal levels of glycerol (0.50%), peptone (0.68%), yeast extract (0.39%), sodium L-aspartate (0.58%), KH2PO4 (0.36%) and K2HPO4 (0.39%) were determined. Aspartase activity (136.57 U/g wet wt.) and biomass yield (0.969 OD600) obtained by using the optimal concentrations of media constituents were in good agreement with the predicted values. This is the first report on employment of RSM for production of aspartase from Aeromonas media NFB-5 and can be very useful for scale-up studies.