Effects of K2HPO4 on the Growth of Nostoc Flagelliforme in Liquid Media with Different Carbon Sources

Liquid fermentation is a promising strategy for sustainable production of Nostoc flagelliforme cells. In order to elucidate whether phosphate could promote the growth of N. flagelliforme in liquid fermentation, the effects of K2HPO4 on N. flagelliforme growth were investigated in liquid media with 15 mM NaHCO3 and 20 % CO2(v/v), respectively, in this study. Results showed that K2HPO4 could promote N. flagelliforme growth under culture conditions with both kinds of carbon sources, respectively. The optimal concentration of K2HPO4 for growth and protein contents of cells is 40–60 mg/L for the existence of each carbon source. The maximum dry cell weights of 0.75 g/L and 1.19 g/L were achieved in media with 15 mM NaHCO3 and with 20 % CO2, respectively, when the concentration of K2HPO4 is 60 mg/L. In media with 15 mM NaHCO3, the photosynthetic and respiration rates’ uptake of nutrients and protein contents increased significantly when K2HPO4 concentration increased to 60 mg/L and then reached a plateau, however, higher concentrations of K2HPO4 inhibited EPS accumulation. By contrast, in media with 20 % CO2, all growth characteristics above of N. flagelliforme were promoted, and reached a plateau at higher K2HPO4 concentrations. These results provide valuable information for the cultivation of N. flagelliforme cells.