Effects of citric acid on cell growth and schizophyllan formation in the submerged culture of Schizophyllum commune

Cell growth and schizophyllan formation of Schizophyllum commune were greatly influenced by the citric acid. Effects of citric acid on schizophyllan batch culture were investigated in the batch cultures by citric acid supplemented initially from 0 to 5 g/L. The cell growth rate was decreased from 0.85 to 0.36 day ^-1, the product yield was enhanced from 0.097 to 0.173 g/g, and specific product yield was enhanced from 0.21 to 0.39 g/g as the citric acid increased from 0.0 to 5.0 g/L. These results indicated that cell growth was inhibited but schizophyllan formation was stimulated by the citric acid. The product formation kinetics was mixed-type kinetics, and the behavior of product formation was likely to be growth-associated as the concentration of citric acid increased. An improved two-stage SPG with co-supplement of glucose and citric acid was proposed and validated in this study. As a result, higher product yield 0.6 g/g was obtained in the second stage of the process, and higher productivity 0.66 g/L hr was obtained. These results suggest that the co-existence of glucose and citric acid in the medium is essential for SPG synthesis.