Production of exopolysaccharide by Ganoderma lucidum in a repeated-batch fermentation

Exopolysaccharide (EPS) productivity of the slow-growing Ganoderma lucidum BCCM 31549 mushroom was enhanced in repeated batch fermentation (RBF) process by reducing the fermentation time. The results showed that by using 2.5-L STR unbaffled bioreactor, the fermentation time could be reduced from 10 days per batch to 5 days, due to lag-phase elimination by adopting a RBF strategy. RBF approach was also shown to achieve a semi-continuous mode of production by eliminating the inoculation time between each cycle. The fermentation period was shortened from 50 to 25 days in five consecutive cycles of RBF, with the productivity of EPS increased from 0.81 g/L day^-1 to 1.32 g/L day^-1 by using N-limiting medium. The presence of clamp connections in RBF ensures the reproducibility of this strategy. The proposed strategy proved to provide easy operation and thus can be adapted for EPS production.