Study On Harvesting Of Heterotrophic Chlorella By Flocculation

Chlorella protothecoides is a kind of single-celled algae that can grow autotrophically.Because of its fast breeding and large amount of oil in cells,it has been widely used in the production of biodiesel.However,the heterotrophic culture of chlorella has the advantages of rapid growth,high density of algal fluid,high oil production and strong controllability,which has great potential research value.Whether autotrophic or heterotrophic,the high cost of harvesting chlorella is a major obstacle to its industrial production.At present,the research on the collection of microalgae mainly focuses on the collection of autotrophic algae,while the research on the collection of heterotrophic chlorella is very few.In this article,heterotrophic chlorella was used as raw material to study the effects of harvesting cells by chemical flocculation and biological flocculation,so as to provide certain experimental data and basic basis for the industrial collection of heterotrophic chlorella.The main research contents and results of this article are as follows:1.Having explored the harvesting effect of seven common industrial flocculants on heterotrophic chlorella.The results showed that when the addition amount is 0.05~0.30 g/100 mL,aluminum sulfate,alum,polyacrylamide and AGAR have no obvious effect on the collection of heterotrophic chlorella,and chitosan has an unsatisfactory collection effect on heterotrophic chlorella.The optimum conditions for ferric chloride harvesting of heterotrophic chlorella were 0.10 g/100 mL addition and 60 min flocculation,then the recovery ratio was 91.01%.The optimum conditions for calcium hydroxide harvesting of mature heterotrophic chlorella were 0.10 g/100 mL and 20 min,then the recovery ratio was99.66%.In addition,having explored the effect of pH on the collection of heterotrophic chlorella.The results showed that the alkaline environment adjusted by sodium hydroxide was favorable for the recovery of heterotrophic chlorella,and the highest recovery ratio was 95.49% at the flocculation time of 60 min when the pH value was 12.2.Sodium hydroxide was used as a basic flocculant to investigate the main factors affecting the collection of heterotrophic chlorella by sodium hydroxide.And the orthogonal experiment was optimized on the basis of single factor experiments.The resultsshowed that the time of chlorella micrococcus culture,sodium hydroxide addition and flocculation time had great influence on the recovery ratio,while the agitation speed,agitation time,and the concentration of algal solution had little influence on the recovery ratio.The optimum harvesting conditions were: 0.15 g/100 mL sodium hydroxide,75 min flocculation,250 r/min agitation,2 min agitation,and under these conditions the recovery ratio was 98.99%.3.Having explored the influencing factors on the harvesting of heterotrophic chlorella by penicillium.Results showed that the optimal conditions for harvesting heterotrophic chlorella by the penicillium were: initial glucose content was 40 g/L,initial pH value was 6,table speed was 200 r/min,culture temperature was 35 ?,incubation time was 7 d,and under these conditions the recovery ratio was 59.62%.