Optimization Of Combined Process Of Microalgae Oil Extraction And Lipase Catalytic Conversion

Microalgae become an excellent raw material for biodiesel production because of its fast growth rate,high oil production and no occupation of cultivated land.Now the production of biodiesel is mainly done by acid/base catalysis.However,the problem that the catalyst cannot be recovered and the environment is destroyed cannot be solved well.Moreover,the use of microalgae to produce biodiesel has a large energy input and is economically inferior.Therefore the immobilized lipase was used as a catalyst to optimize the process conditions for the production of biodiesel by in situ transesterification of microalgae.The feedback is adjusted by mutual feedback between fat extraction and transesterification.Provide reference for optimization of biodiesel process parameters for biocatalyst catalysis,and lay a foundation for improving the economics of microalgae biodiesel industrialization.The cell wall-deficient Chlamydomonas.reinhardtii CC-503 was used as a raw material.Firstly,the culture conditions for increasing the yield and oil content of the microalgae were screened.Four methods for increasing the content of microalgae oil were compared.It was found that compared with the addition of active oxygen inducer,nitrogen-deficient culture can effectively increase the oil content of C.reinhardtii CC-503,but the microalgae biomass decreased.The normal culture in the early stage increased the biomass of microalgae,and the nitrogen deficiency culture in the later stage increased the oil content of microalgae as the optimized production condition of the oil-rich microalgae.The aim is to provide quality materials for the production of microalgae biodiesel.Secondly,the peanut oil with the main component of neutral fat was used as a model to study the characteristics of immobilized lipase transesterification.The immobilized Pseudomonas cepacia lipase was used as a biocatalyst.The orthogonal experimental design found that the optimal process conditions were different when no hexane was added or added.The optimal process conditions without adding n-hexane were determined as follow,reaction time,alcohol to oil ratio,enzyme dosage,temperature and water volume were 48 h,3:1,450 mg,35℃,and 0.24 m L respectively.Under this condition,the conversion of total fatty acid methyl ester was 90.58%.The optimal process conditions adding n-hexane were determined as follow,reaction time,alcohol to oil ratio,water volume and mass ratio of n-hexane to methanol were 48 h,5:1,0.30 m L and 1:4 respectively.Under this condition,the conversion of total fatty acid methyl ester was 60%.It lays a foundation for the design of the combined process parameters of microalgae oil extraction and lipase catalytic conversion.Finally,the optimal process conditions for the production of biodiesel by in situ transesterification of microalgae oil were explored,and the mutual feedback was verified by microalgae oil extraction and fat conversion.The study optimized the optimal reaction conditions for the in situ extraction of transesterification of microalgae oil,and the stability of immobilized lipase reaction,which screening by extraction solvent,extraction component conversion characteristics,single factor experimental study,and response surface analysis.Hexane/methanol(v/v)=2:1 is suitable for the extraction of microalgae oil and can be efficiently converted into the most suitable solvent for biodiesel production.The optimal process conditions were determined as follow,hexane/methanol(v/v),reaction time,enzyme dosage,temperature and water volume were 2:1,36 h,360 mg,41℃,and 1m L respectively.Repeated experimental verification showed that the highest conversion rate can reach 100%.Under the optimal reaction conditions,the immobilized Pseudomonas cepacii lipase can be efficiently reused 7 times.The results laid a foundation for the in situ extraction of microalgae oil by immobilized lipase to catalyze transesterification to produce biodiesel.