Fed-batch gluconic acid production from Penicillium variabile P16 under different feeding strategies

Penicillium variabile P16 is characterized by the ability to release high levels of glucose oxidase when grown in glucose-rich media converting, at the same time, glucose into gluconic acid. This work reports on gluconic acid production by the above strain grown in bench-top reactor under different strategies, traditional batch and fed-batch processes; Na2CO3 was substituted for CaCO3 as the buffering agent in order to prevent calcium gluconate precipitation over the mycelium that would limit oxygen uptake and, as a consequence, glucose conversion. Best results were obtained with an improved fed-batch process which, in addition to glucose, was continuously fed with nitrogen and minerals at a flow rate of 0.02 ml min−1: yield and total productivity were 99.4% and 2.02 g h−1, respectively, and remained constant till the end of the fermentation (240 h).