Research On The Continuous Production System Of Algae-lysing Active Substances

Rapid development of industrial and agricultural production,over-exploitation of the marine environment and population increasing are aggravating marine ecology and causing red tide emergence frequently.The red tide phenomenon polluted the ecological environment,affected human health,and caused economic losses.Studying the emergency prevention and control strategy against the outbreak of red tide is the most important issue to solve the red tide hazard.The algicidal strategy includes a variety of physical,chemical and biological methods.Among these methods,biological methods are potential due to its characteristic of environment friendly.In the study,an algicidal Vibrio Z115,which appearance with the ability of algicidal compounds production,was studied in order to obtain an environmentally friendly method for continuous algicidal compounds production.The cultivation method of Vibrio Z115 and target red-tide Akashiwo sanguinea were optimized.The cultivation medium of Vibrio Z115 was contained 18.25g/L NaCl and 18.75 g/L Na₂SO₄.The fermentation temperature and initial pH were controlled at37?and 7.5 respectively.This study compared the fermentation results at different carbon source addition as well,when the glucose used as carbon source,the minimum fermentation broth addition of 2%?v/v?could obtain almost 100%algae-killing.In addition,the cultivation medium of Akashiwo sanguinea was f/2 medium with an initial pH of 7.5-8.5.The cultivation condition was controlled at 22?,the light intensity was 70?mol/m²/s,the light-dark ratio was 12:12.After cultivation methods optimization,a continuous fermentation systems based on CSTR was set up for effective continuous production algicidal activity compounds.And the fermentation broth would use for red-tide algae killing.The continuous fermentation system ran for almost 60 day.When dilution rate was 0.023 h^-1,the OD₆₀₀00 was 4.06±0.82,fermentation broth addition of 0.3%?v/v?could lyse the red-tide algal cell totally.After increase the dilution rate to 0.1 h^-1,the algicidal activity compounds were not decreased obviously,thus,the optimal dilution rate of this CSTR was 0.1 h^-1.We also investigated the effect of glucose concentration for algicidal compounds production.When the glucose concentration was 2 g/L,the OD₆₀₀00 was4.18±0.72,maximum algicidal rate was 99.71±0.66,after increasing glucose concentration,the OD₆₀₀00 and algicidal activity of fermentation broth were not increase obviously.For further improve the production ability of CSTR system,bacteria cells were immobilized with polyving akohol?PVA?.Consider of particle stability,shape and cross-link,1799 PVA with polymerization of 2000 was employed for bacteria immobilization.For continuous fermentation using immobilized bacteria,the particle addition was 40 g and the working volume of reactor was 200 mL.When the dilution rate was 0.071 h^-1,the OD600 was 2.99±0.31,pH was 7.91±0.17,and the minimum fermentation broth addition was 2%?v/v?for totally algal cell killing.When increase the dilution rate to 0.1 h^-1,the OD600,pH and algal cell killing were not decrease greatly.Continue increase the dilution rate to 0.25 h^-1,the system can still operate normally.These results demonstrated that higher productivity could be obtained by employing immobilized bacteria.Finally,we sprayed the fermentation broth at different temperatures.Higher than a temperature of 185?would let the algicidal activity losing and the spray temperature was 120?.The dose-response curve of algicidal powder to Akashiwo sanguinea was calculated as Y=5.6518+4.0182*logZ?R2=0.81?.The threshold,EC₅₀,EC₉₀0 were 0.17,0.68 and 1.43 g/L.Physiological activity in algicidal powder to Akashiwo sanguinea were investigated to elucidate the mechanism,because of an increase of reactive oxygen species?ROS?in algal cells,the activities of the antioxidant enzymes superoxide species?SOD?,malodialdehyde?MDA?were enhanced under ROS stress,the activity of catalase?CAT?always keep decreasing.