Study On Cultivation Of Isochrysis Zhangjiangensis With Tubular Photobioreactor

Isochrysis zhangjiangensis has great application value,not only can be used for fish and shellfish larvae good foundation feed, but also be used for food manufacture,pharmaceuticals, bio-energy and other fields. Good photobioreactors suitable for mass cultivation are the foundation of comprehensive development of I. zhangjiangensis. The major works and conclusions of this study are summarized as follow:(1) The main culture conditions of I. zhangjiangensis were optimized. In order to achieve the high density growth of I. zhangjiangensis and determine the appropriate culture conditions, the main cultivation conditions were tested with small culture vessels.The results showed that the optimal concentrations of NaNO3 and KH2PO4 were 300mg/L and 20mg/L, respectively, and I. zhangjiangensis grew best in the medium with n/p ratio of15:1. It also showed that I. zhangjiangensis could grow below the CO2 concentration of20%, and it was able to get better growth in the range of 5%~10%(v/v) of CO2 concentration. Moreover, I. zhangjiangensis exhibited ability to adapt different light intensity, but it grew best under the light intensity of 5000~9000lx.(2) An indoor experimental system was built, which involved lighting system,ventilation system and temperature control system. Three kinds of photobioreactors, with40, 50 and 70 L of cultivation volume respectively, were designed and built in the paper.(3) In order to test application properties of the three kinds of photobioreactors, the advantages and disadvantages of different structures and effects on I. zhangjiangensis growth, different comparative culture tests were carried out based on the photobioreactors.Firstly, a contrast scale-up culture experiment was carried out, and the results showed that the cell growth rate and the specific growth rate of I. zhangjiangensis were improved by the increases of 17.84% and 9.64% respectively while scaling up 100 times. Secondly, a contrast experiment of two kinds of air supply ways was studied, and the results showed that the quartzitic sandstone bubbler was better than the micropore tube bubbler, and that the cell growth rate and the specific growth rate of I. zhangjiangensis increased 23.21%and 10.73% respectively. Finally, a contrast experiment of pipe arrangement form of photobioreactor was studied, and the results showed that vertical tube was better than horizontal tube, which the cell growth rate and the specific growth rate of I.zhangjiangensis were improved 43.45% and 12% respectively in the same culture conditions.(4) The optical attenuation in the algae suspension of I. Zhangjiangensis was studied by measuring the changes of light intensity passed different distances through algae suspensions of different concentrations. A light attenuation model was built as E = E0exp[-(0.23OD500+0.038)L] according to Lambert-Beer law, and the results showed that along with the increase of I. Zhangjiangensis cell concentration and optical path, the optical attenuation was increased. The optical attenuation increased 35.8% when the cell density increased 6 times in the same pipe diameter.(5) Mass mixing and flow patterns in the photobioreactor were studied. The gas flow rate in the photobioreactor was optimized, the result showed that cell density reached 2.88×107/L after 7 d cultivation in the ventilation rate of 2 L/min, the result also showed that along with the increase of cell concentration, the flow rate of the cultivation broth decreased in the same ventilation rate.