Mutation And Selection Of The Oil-Rich Strain Of Chlorella Emersonii

Chlorella is a kind of single-cellalgae with many excellent characteristics such as fast growth rate and high nutrition content. Increasing research reports indicate that Chlorella also has potentials as raw materials for biodiesel production.. However, wild-type strains of Chlorella may be unsuitable for industrial culture to produce biodiesel because of their relative lower biomass and oil yields. Therefore, it is crucial to make genetic improvement on wild-type algae for breeding industrial algae strains. In this study, wild-type Chlorella emersonii isolated from aquatorium in Shanxi province, China, was selected for UV-EMS combined mutation to obtain excellent Chlorella strains with high biomass and oil yields.The main findings were listed as the followings:Firstly, the sensitivity of Chlorella emersonii to 11 kinds of antibiotics was investigated. Streptomycin with minimal lethal concentration of 7.5 ?g/ml was selected as screening antibiotic in mutation breeding. By doing this kind of screening for mutants,, labour work of screening was decreased by 30%, and however, the screening efficiency was increased by 40% compared to non-antibiotic screening method.Secondly, sterile culture system of Chlorella emersonii was established with the use of antibiotics, and further optimized. The favorable culture conditions in this system included the initial OD 0.2, pH range 8.5-9.5, temperature 25±0.5?, and salt concentration<0.01 mol/L.Thirdly, two mutant strains of Chlorella emersonii labled as #028 and 033 were identified as excellent mutant strains favorable for industrial production from the mutation population generated by EMS-UV treatments. The total fatty acid (TFA) content and monounsaturated fatty acid (MUFA) level in #028 strain were 52.57%(dry weight,DW) and and 35%, respectively. TFA and MUFA contents in #028 strain increased by 1.69 and 4.37 folds compared to the starting strain. The TFA and MUFA contents in #033strain were 48.74% and 15%, which were 1.63 and 1.87 times higher than that of the starting strain.Finally, the growth and development performance of the two mutant strains were further characterized in this study.In comparison with wild-type starting strain, the two mutant strains demonstrated significantly improvements in the growth rate, photosynthetic efficiency and maximum photosynthetic capacity. Technology of bacterial-free culture and UV-EMS mutagenesis of Chlorella emersonii developed in this study could be used as valued reference, and the two excellent mutant strain obtained here would be used in industrial cultivation for biodiesel production.