Control strategy of pH,dissolved oxygen concentration and stirring speed for enhancing β‐poly (malic acid) production by Aureobasidium pullulans ipe‐1

BACKGROUND: β‐poly(malic acid) (PMLA) can be used as a pro‐drug or for a drug‐delivery system. Effects of pH, dissolved oxygen concentration (DO) and stirring speed were investigated to improve PMLA production by A. pullulans ipe‐1. RESULTS: The strain produced a high PMLA concentration when pH and DO remained at about 6.0 and above 70%, respectively, and the yeast‐like cells were the main PMLA producers. To further promote PMLA production, the cultivation could be divided into three phases. In phase I, cell growth was accelerated by maintaining high DO (>70%) with a constant stirring speed of 800 rpm. In phase II, PMLA production was increased by controlling DO at 70% using the automatically controlled stirring speed. In phase III, PMLA production on per gram of glucose (Y_p/s) was enhanced by keeping DO at 70%, and using a low stirring speed to decrease cell growth. Compared with batch cultures, a higher PMLA yield was obtained with this strategy, i.e. PMLA production and Y_p/s increased by 15% and 18%, respectively. CONCLUSION: Control strategies for pH, DO and stirring speed provide a good reference for process development and optimization of PMLA production. © 2012 Society of Chemical Industry