Effects of K_2HPO_4 on the Growth of Nostoc Flagelliforme in Liquid Media with Different Carbon Sources

摘要

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 K_2HPO_4 on N. flagelliforme growth were investigated in liquid media with 15 mM NaHCO_3 and 20 % CO_2(v/v), respectively, in this study. Results showed that K_2HPO_4 could promote N. flagelliforme growth under culture conditions with both kinds of carbon sources, respectively. The optimal concentration of K_2HPO_4 or 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 NaHCO_3 and with 20 % CO_2, respectively, when the concentration of K_2HPO_4 is 60 mg/L. In media with 15 mM NaHCO_3, 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 K_2HPO_4 inhibited EPS accumulation. By contrast, in media with 20 % CO_2, all growth characteristics above of N. flagelliforme were promoted, and reached a plateau at higher K_2HPO_4 concentrations. These results provide valuable information for the cultivation of N. flagelliforme cells.