Regulative Effect Of L-carnitine On The Population Growth And Photosynthetic Pigment Synthesis Of Marine Chlorella Sp.

The effects of L-carnitine on population growth and photosynthetic pigments synthesis of marine Chlorella sp.were studied,which provided theoretical support for exploring the mechanism of exogenous L-carnitine promoting population growth of marine Chlorella sp.In this experiment,marine Chlorella sp.was taken as the research object.Artificial basic seawater and f/2 medium were used as nutrient sources.L-carnitine of 0(control),5,50,100,200 mg/L was used to enrichment culture for 10 days.The population density was measured every day.At the end of the experiment,all samples of marine Chlorella sp.were collected and their population growth,the content of Fe and Mg elements,the composition of photosynthetic pigments and the renaturation of pigments were detected.Antioxidant capacity of synthase and expression of key synthase genes.The results show that:(1)Effects of L-carnitine on population growth,Fe?Mg content and pigment composition of marine Chlorella sp.Under the experimental conditions,during the plateau phase,the population density of marine Chlorella sp.in the 5 mg/L L-carnitine group increased significantly(P<0.05),and the population density in the 200 mg/L L-carnitine group was significantly lower than the control group(P<0.05).During the exponential growth phase,the specific growth rate of marine Chlorella sp.in the 5,50 mg/L L-carnitine group was significantly higher than the control group(P<0.05).The specific growth rate in the 200 mg/L L-carnitine group was significantly lower than the control group(P<0.05).The content of Fe of marine Chlorella sp.in 5,50 mg/L L-carnitine group was significantly higher than the control group(P<0.05).The content of Fe in 200 mg/L L-carnitine group was significantly lower than the control group(P<0.05).The Mg content of marine Chlorella sp.in the 5 mg/L L-carnitine group was significantly higher than the control group(P<0.05).The ?-carotene content of marine Chlorella sp.in the 5,50 mg/L L-carnitine groups were significantly higher than the control group(P<0.05),and the ?-carotene content in the 200 mg/L L-carnitine group was significantly lower than the control group(P<0.05).The lutein content and astaxanthin content of marine Chlorella sp.in the 5 mg/L L-carnitine group were higher than the control group,but there was no significant difference(P>0.05).(2)Effect of L-carnitine on the antioxidant capacity of pigment-protein complex of marine Chlorella sp.The scavenging ability of DPPH free radicals of marine Chlorella sp.in the 5,50 mg/L L-carnitine groups were higher than the control group,but there was no significant difference(P>0.05).The scavenging ability of superoxide anion free radical of pigment-protein complex in 50 mg/L L-carnitine group was significantly higher than the control group and other L-carnitine groups(P<0.05).The scavenging ability of superoxide anion free radical of 5,100,200 mg/L L-carnitine groups were significantly higher than the control group(P<0.05).The hydroxyl radical scavenging ability of pigment-protein complex in the 5,50 mg/L L-carnitine groups were significantly higher than the control group and other L-carnitine groups(P<0.05).The lipid peroxidation inhibitory activity of 50,100 and 200 mg/L L-carnitine pigment-protein complex were significantly higher than the control group and 5 mg/L L-carnitine group(P<0.05).The metal chelating ability of pigment-protein complex in the 5,50 mg/L L-carnitine were significantly higher than the control group.(3)Effects of L-carnitine on the expression of key synthase genes of photosynthetic pigments on marine Chlorella sp.The relative expression of PSY mRNA of marine Chlorella sp.in 5,50 mg/L L-carnitine group was significantly higher than the control group(P<0.05).The relative expression of PSY mRNA in 100,200 mg/L L-carnitine groups were lower than the control group,but there was no significant difference(P>0.05).The relative expression of CHLD mRNA of marine Chlorella sp.in 5,50 mg/L L-carnitine groups were significantly higher than the control group(P<0.05).The relative expression of CAO mRNA of marine Chlorella sp.in 5,200 mg/L L-carnitine groups were higher than the control group(P>0.05).The relative expression of CAO mRNA in 50,100 mg/L L-carnitine groups were lower than the control group(P>0.05).In conclusion,the suitable concentration of L-carnitine can increase the content of Fe and Mg,increasing the activity of PSY,CHLD and CAO of marine Chlorella sp.,and improve the free radical scavenging efficiency,metal chelation,and lipid peroxidation inhibitory activity of the pigment protein complex.To inhibiting the degradation of pigments,in order to regulate the photosynthetic pigment synthesis of marine Chlorella sp.,thereby promoting its population growth.