Evaluation of medium composition and fermentation parameters on pullulan production by Aureobasidium pullulans.

摘要

The goal of this study was to enhance pullulan production by evaluating the effects of different fermentation parameters. Various carbon sources and their concn., yeast extract (YE) concn., fermentation temp. and pH profiles were examined. Optimal growth conditions for pullulan production by Aureobasidium pullulans ATCC 201253 were found to include 75 g/l of sucrose as carbon source and 3 g/l of YE at 30 degrees C. Under these conditions, with an initial pH of 5, a final pullulan concn. of 20.7 g/l and a max. production rate of 0.22 g/l/h were achieved. Various pH profiles, agitation speeds and aeration rates, as well as fed-batch fermentation were also evaluated. Pullulan production was enhanced to 25.8 g/l after cultivation for 7-days with a 0.68 g/l/h max. production rate. There was no significant improvement of pullulan production from fed-batch fermentation. Optimal kinetics parameters were as follows: initial pH 2.0, switched to pH 5.0 after 72 h and kept constant; agitation speed of 200 rpm; and aeration at 1.5 vvm. Quality analysis demonstrated that the pullulan content produced under optimal conditions was 94.5% and its viscosity was 2.3 cP. FTIR spectroscopy also suggested that pullulan predominated in the exopolysaccharide fraction produced.