The Effect Of Salinity And Alkalinity Stresses On The Antioxidase And Metabolite Production Of Scenedesmus SP-01

This experiment was to investigate the effect of different stress of NaCl,NaHCO3and pH on the growth, antioxidant enzymes, pigments and fatty acids ofScenedesmus SP-01, isolated from Guangzhou Liuhua Lake. Meanwhile, themorphological taxonomy and18S rDNA molecular marker were further studied toidentify the Scenedesmus SP-01. The main results were as follows:1. Under both light and transmission electron microscopy, the shape ofScenedesmus SP-01was almost ovoid, the cell wall was smooth without flagella,containing cyteblast, cup-shaped chloroplast, chlorophyll a and chlorophyll b, severalstarch grains and one pyrenoid were detected. Besides, through sequencing analysisand phylogenetic analysis of18S rDNA sequence, Scenedesmus SP-01was identifiedas an objective oculate Chlorophyta Scenedesmus family Scenedesmus. And SP-01might be a new species of genus, but which need further study.2. Scenedesmus SP-01grew well in the culture containing NaCl from0to0.10mol/L, and with the highest cell dry weight0.73g/L at0.01mol/L NaCl，whichshowed that low NaCl concentration promoted the growth of SP-01. However, withthe increase of salinity-stress the growth of SP-01began to decline, and acquired thelowest cell dry weight0.21g/L at0.60mol/L NaCl. Moreover, different kind ofalkalinity stress caused significant differences on the growth of SP-01(p<0.05). It was detected that the optimal range of NaHCO3for the growth of SP-01were among0.05-0.10mol/L, and reached the highest cell dry weight0.84g/L at0.05mol/LNaHCO3，which showed low NaHCO3concentration promoted the growth of SP-01.The growth of SP-01falled significantly at the concentration of0.25mol/L NaHCO3,and falling further with the raise of NaHCO3stress. SP-01showed a wide range ofalkalinity stress, the optimal range of pH for the growth of SP-01were from pH7.5topH10.5, and the cell dry weight fluctuated from0.60g/L to0.69g/L, even maintainedconsiderable growth at initial pH11.5.3. The activities of SOD and CAT of SP-01reacted the same variation tendencyon salinity and alkalinity stress. Both SOD and CAT activities had an ascending trendwith the increasing stress of low salinity and alkalinity. However, the activities ofantioxidant enzymes gradually decreased with the further increased stress, whichcaused significant differences of activities of antioxidant enzymes (p<0.05).Oppositely, the increasing low salinity and alkalinity stress caused accumulation ofcarotenoids, mainly containing lutein and astaxanthin, both acquired the highestpigments contents at0.10mol/L NaHCO3and pH9.5, but with further stress,catotenoids began to fall.4. It was found that total fatty acid content showed positive relationship with thegrowth of SP-01. TFA increased with the accumulation of cell dry weight, anddecreased with the fall of cell dry weight. TFA reached the highest TFA content266mg/g at0.10mol/L NaCl, and C18:1contains47%of TFA.