Trophic Niche Of Isochrysis Zhanjiangensis On Organic Carbon Compounds

Isochrysis zhanjiangensis belongs to Chrysophy, Prymnesiophyceae, Isochrysidales,Isochrysidacea, Isochrysis, which is an economic microalga. The characteristics of themixotrophic growth ofⅠ. zhanjiangensis were studied by using diverse organic carboncompounds with different concentrations in f/2 culture medium. The organic carbon compoundsused in this study included glucose, sodium acetate, galactose, glycerin, ethanol, sodium citrateand glycin. The cell density, biomass and contents of protein and total lipid ofⅠ. zhanjiangensiswere also monitored under the treatments of glucose and sodium acetate with 14 concentrationlevels. Our results indicated that Isochrysis zhanjiangensis showed some certain selectivity tothe organic carbon compounds. Although it could utilize all the organic carbon compounds formixotrophic growth, the capacity of different organic carbon compounds to promotemixotrophic growth varied in the experiments. Glycin facilitated the growth of Isochrysiszhanjiangensis, while ethanol, did not exhibit any remarkable effects on the growth: Besides,there were different effects of organic carbon compounds on algal growth in differentconcentrations. When the initial concentration of organic carbon compounds was ranged in0.5-10g·L^-1, lower concentrations of glycin displayed better effects on the cell growth ofⅠ.zhanjiangensis, whereas intermediate concentrations of ethanol, sodium citrate and glycerin orhigher concentrations of glucose, sodium acetate and galactose had obvious promoting effectson the growth ofⅠ. zhanjiangensis. The culture mediums using glucose or sodium acetate asorganic carbon sources could sustain the mixotrophic growth ofⅠ. zhanjiangensis at very wideconcentrations. With the increasing concentrations of glucose or sodium acetate, cell density,biomass and contents of protein and total lipid ofⅠ. zhanjiangensis were increased slightly atfirst and then decreased obviously, which suggested that high concentration of organic carboncould bring negative effects on the growth ofⅠ. zhanjiangensis. The optimum range of glucoseconcentration was within 10-15g·L^-1; suboptimum ranges were 0.5-10g·L^-1 and 15-50g·L^-1, andunsuitable range was within 50-200g·L^-1. For sodium acetate concentration, however, theoptimum range was between 5 g·L^-1 to 10g·L^-1; suboptimum ranges were 0.5-5g·L^-1 and10-30g·L^-1, and unsuitable range was 30-200g·L^-1. The maximum contents of protein and total lipid were found in the low concentration of glycin (0.5g·L^-1), high concentration of glucose(15g·L^-1) and high concentration of sodium acetate (7.5g·L^-1). Our results can provide somescientific information for high density cultivation of Isochrysis zhanjiangensis.