Optimization Of Chlorella Growth In Column Photobioreactor Bubbled With Air

In order to investigate the optimum culture conditions for the mass production of microalgae in a column-type bubbling photobioreactor,this paper uses the experimental method to cultivate the Chlorella in a self-designed and established cylindrical bubbling photobioreactor.The growth of Chlorella under different input conditions was studied from three aspects:CO₂ concentration,light/dark cycle and propeller stirring speed.This study aims to provide experimental reference for enhancing the growth rate for large-scale mass cultivation of Chlorella in the column-type bubbling photobioreactors.The main results are as follows:Firstly,in order to find the most suitable CO₂ concentration for the growth of Chlorella,we conducted 0.035%,5%,10%,15%,20%as the five different concentrations for the experiment.Compared to pure air（CO₂ concentration of 0.035%）,the increase in CO₂ content in the feed gas to 5%can significantly promote the growth of Chlorella,which was almost twice of that under the condition of pure air culture.The maximum biomass is 4.001×10⁶cell/mL.With the increase of the concentration of CO₂,the growth of Chlorella will be different degrees of weakening.In general,the concentration of CO₂in the range of 0-5%is conducive to the growth of Chlorella.Secondly,four different experiments on light/dark cycle are carried out in this paper,that is,24:0,18:6,12:12 and 6:18（L:D）.The results indicated that the growth of Chlorella under 24:0 was the best with the highest biomass of 4.649×10⁶cell/mL.At the same time,we also found that in the same light/dark conditions,the appropriate increase in the light intensity is also helpful to strengthen the photosynthesis efficiency of Chlorella,thereby increase the maximum biomass.Finally,we conducted a study on the propeller agitation speed of the impeller in the column-type bubbling photobioreactor.The results showed that when the rotation speed was small,Chlorella remained the normal growth state,and when the rotation speed was large,the growth of Chlorella was affected.At the five rotational conditions studied,Chlorella showed the best advantage in terms of the maximum growth rate and biomass when the rotational speed was moderate at 90 rpm,at which the highest biomass is 4.667×10⁶cell/mL.Compared to the biomass of all the experimental groups without previous propeller,it has been shown that the presence of the stirring device in the column-type bubbling photobioreactor has a positive effect on the growth of Chlorella.