Breeding Of Chlorella With High Lipid Content And The Study Of Gene Expression Related To Lipid Synthesis

The need to develop alternative biodiesel is clear-cut.Not only are fossil fuels limited resources but also burning them produces carbon dioxide,which is one of the causes of global warming.Currently,microalgae have been identified as a superior feedstock for biodiesel production.These approaches accomplishes the selection of oil-rich algae strains through mutation breeding and provide quality algae strains to solve the bottleneck problem in production and experimental and theoretical basis for the development of biodiesel industry.Quality mutants were obtained from Chlorella vulgaris HD01 by mutagenesis treatment of UV mutagenesis and EMS mutagenesis.In order to examine the lipid accumulation process in mutants,the study detected different enzyme activity with assay kits including acetyl coenzyme A carboxylase,diacylglycerol acyltransferase,acetyl coenzyme A synthetase,glycerol phosphate dehydrogenase,phosphoenolpyruvate carboxylase,diphosphate glucose pyrophosphorylase,sedoheptulose-1,7-bisphosphatase and rubulose-1,5-bisphosphate carboxylase.Then the mRNA expression of acc were tested using quantitative PCR in order to prove the relationship between lipid synthesis key enzyme gene acc and lipid synthesis in microalgae.Compared to the wild type,the lipid accumulation of C02 and special growth rate of C06 were individually increased 44.0% and 107.93%.And the lipid accumulation and special growth rate of E33 were increased by 63% and 1.39%.The activities of different key enzymes of Chlorella vulgaris HD01 and mutants gradually decreased and the fourth day to eighth day was a critical period of enzyme avtivity changes.The relative expression of acc gene in Chlorella vulgaris HD01,mutant C02 and mutant C06 were increased first then decreased and reached the highest expression in the 8th day.The relative expression of acc gene in C02 and C06 just reached as 11.57% and 22.14% the same as in Chlorella vulgaris HD01.This research studied the mutants obtained from mutagenesis treatment of UV mutagenesis and EMS mutagenesis.It can be found that UV mutagenesis and compound mutagenesis had an effect on lipid accumulation and special growth rate,respectively.Enzyme activity changes in the mutants were studied and found that enzyme activity gradually decreased and the mRNA expression of acc had no obviously effection on the lipid accumulation.The lipid accumulation in Chlorella vulgaris was a result from all key enzyme effection.