P42: Optimization of carbon/nitrogen ratio of production medium and oxygen mass transfer rate for enhanced production of exopolysaccharides by mycelial cells of Schizophyllum commune in 500L pilot-scale bioreactor

Bioprocess scale-up from laboratory to pilot-scale was successfully carried out for mass production of exopolysaccharide(EPS), an active ingredient for skin moisturizer produced by mycelial cells of Schizophyllum commune in submerged cultures. For development of a pilot-scaled bioprocess, the effects of various environmental factors on EPS production and cell growth were investigated, firstly in both 250ml shake-flask and 5L bioreactor cultures. C/N ratio was observed to have the most significant influences on the EPS biosynthetic capability of the high-yielding mutants. With the increment of the C/N ratio, the EPS production was also enhanced, and vice versa. In the shake-flask fermentations, 15g/L of EPS was produced at the C/N ratio of 27:1, which had been statistically determined through response surface method (RSM). Unfortunately, when the parallel fermentations were performed in 5 liter bioreactors under the identical culture conditions to the shake flasks, almost 40% reduction in the EPS productivity was demonstrated, plausibly due to the apparent differences of oxygen mass transfer coefficient (k_La) between the two culture systems. Therefore, various agitation conditions (150, 200, 250rpm) and C/N ratios were reexamined in the 5L bioreactor cultures, resulting in almost similar level of EPS productivity at the agitation speed of 250 rpm and the C/N ratio of 40:1 to that from the previous shake-flask cultures. By carefully applying all the experimental results obtained from the bench-scale 5 liter bioreactor cultures, it was possible to obtain almost similar level of EPS productivity (18 g/L) in the 500 liter pilot-scaled fermentations.