Study On The Technology Of Cultivating Isochrysis Zhangjiangensis With Floating Photobioreactor

It is imperative to vigorously develop aquaculture to meet the increasing the food requirements due to the depletion of land resources and the rapid increasing global population.Microalgae are essential participants in aquaculture,since it can not only provide abundant nutrients for aquaculture animals,but also plays a significant role in maintaining green water environment for the culture systems.Although the global demand for microalgae productivity as aquaculture bait is rapidly increasing,its productivity is very limited due to high productivity cost and low productivity efficiency of the traditional microalgae productivity methods.A low cost and efficient floating photobioreactor?PBR?cultivation system,namely,bicarbonate-based carbon capture and algal productivity system on ocean?BICCAPSO?was developed in our previous study,which has a great potential for commercial application.The aim of this study is to test the feasibility of using this system to cultivate the microalgae species that is commonly used as aquaculture feed,and I.zhangjiangensis was tested as the example aquaculture feed microalgae species in this study,due to its wide application in aquaculture.Firstly,the effect of bicarbonate concentration on the growth of I.zhangjiangensis was investigated.It was found that the growth of I.zhangjiangensis was the best under the condition of sodium bicarbonate concentration of 5 g/L.By comparing the effects of sodium bicarbonate and carbon dioxide as carbon source and without carbon source,it was found that the control group without carbon source,I.zhangjiangensis grew slowly,and the experimental group with carbon dioxide had the best growth condition,reaching 38.8×10⁶cells/ml,while the experimental group with 5 g/L sodium bicarbonate had 29.3×10⁶ cells/ml.Then,a large-scale culture experiment of 10 m² of floating PBR was carried out on I.zhangjiangensis.First,Compared with different culture depth on the 1 m² floating PBR of I.zhangjiangensis,the highest area productivity was 4.66 g/m²/day under the 10 cm culture depth.Then we carried out comparative culture experiments on the I.zhangjiangensis in open pond,flat panel PBR and floating PBR.It was found that the same productivity could be achieved in the floating PBR with flat panel PBR?P>0.05?.Finally,we selected a semi-continuous operation experiment in which a flat panel PBR?100 L?was compared with a 10 m² floating PBR?1000 L?.Through experiments,we can find that I.zhangjiangensis can be growing in 10 m² floating PBR.The floating PBR can reach the productivity of 0.117 g/L/d,which is the same level of culture as the flat panel PBR?P>0.05?.According to the results,the optimal process for the large-scale cultivation of I.zhangjiangensis based floating PBR was determined The use of sodium bicarbonate as a carbon source can not only saves the carbon cost,but also achieved the same cultivation performance as the 2%CO₂.Based cultures in floating PBR on ocean resulted in productivity at the same level as flat panel at large scale.Floating PBR has the advantages of easy temperature control,large cultivation capacity,and no land requirements,which provides an efficient,cost-effective,and stable microalgae biomass productivity for aquaculture industry.With on site productivity of fresh algae cells as aquaculture feed or inoculums seed in water body for aquaculture,floating PBR provides a better integration between microalgae cultivation and aquaculture.