The Physiological Effects Of Salinity Stress On Fresh Spirulina Platensis

Spirulina platensis has been successfully exploited and commercially produced because of its high economic value.However,mass culture of Spirulina platensis will need large amount of fresh water and mineral nutrients,which leads to high production costs.Spirulina platensis has has been reported to live in various environments with different osmoticum,temperature and salt concentrations,especially in high alkalinity conditions.The country has extreme abundant seawater resources with rich mineral elements,and it is of great importance to study the physiological effects of salt stress on Spirulina platensis to its mass culture with seawater.In this study,Spirulina platensis was domesticated progressively under salt stress,and the changes of the physiological indexes,photo synthetic parameters and trichome morphology of Spirulina platensis were investigated.The domesticated Spirulina platensis can grow in different seawater mediums.Meanwhile,mixotrophic culture was conducted to increase biomass production.The main results are as follows:1.Spirulina platensis was screened,separated and purificated before experiment.Then,the optimum growth conditions were explored based on previous researches.The results showed that the most suitable initial pH is 9.0 to 9,5 and the optimal initial inoculum is 10%.2.Over 6 months of sea salt progressive domestication,the salt-adapted Spirulina platensis which can survive in 3%salt concentrations were obtained.Salt stress had the great influences on some phsiological indexes and trichome morphology.Compared with the control groups,dry weight,chlorophyll-a and phycobiliprotein content were increased,while,the total lipid content did not change significantly.It was noticeable that the accumulation of carbohydrates was increased with salt concentration increasing.Salt stress apparently affected the photosynthesis.The measurement of photosynthetic parameters of Fv/Fm,?,rETRmax and Ik indicated that PS? electron transport activity was inhibited and the PS? system was damaged,which significantly decreased photosynthetic electron transport efficiency and light saturation point.Salt stress made alge filaments shorter and straight,and coiled under high salt concentrations.3.The salt-adapted Spirulina platensis were cultured under laboratory conditions of Zarrouk medium adding different seawater mediums,such as seawater SW1 and seawater SW3 medium.It showed that Spirulina platensis died in SW3 medium.The growth and photosynthetic parameters were similar in ZSW as in SW1 medium,while,fresh Spirulina platensis that directly cultured in SW2 medium grew poorly.The biomass reached the maximum value when added 0.5 g-L--1 glucose as an organic substrate under 3%salinity.