43. 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.