Effect of oxygen supply on the intracellular flux distribution and a two-stage OUR control strategy for enhancing the yield of sodium gluconate production by Aspergillus niger

BACKGROUNDIn this study, the performance of aerobic batch fermentation with Aspergillus niger producing sodium gluconate under different oxygen supply levels through adjusting the agitation rate were investigated. The response of glucose metabolism in A. niger to different oxygen uptake rate (OUR) levels has been studied in the present work. RESULTSMetabolic flux analysis demonstrated that the high oxygen supply condition was favorable for cell growth and initial sodium gluconate synthesis during the early fermentation phases. However, during the late stable phase, metabolic flux analysis indicated that a high yield of sodium gluconate production could be achieved at a medium OUR level of 55 2.5 mmol L-1 h(-1) as less flux was required for glucolysis and the TCA cycle. With a two-stage OUR control strategy, the final sodium gluconate yield of the batch fermentation was enhanced and reached 93.7% (mol vs mol), which was higher than those obtained using a high oxygen supply level throughout the whole fermentation process. CONCLUSIONS Metabolic flux analysis was successfully used in the present work, and the two-stage OUR control strategy increased the yield of sodium gluconate production to 93.7%. (c) 2015 Society of Chemical Industry