| Nowadays, with the deterioration of energy crisis and environment problems, research on new energy and biodiesel has been in the limelight. There are a lot of advantages of micro-algae, such as high biomass、short life cycle、easy to culture and contain many lipids among large number of organisms, so it is believed to be one of the energies which can be recycle and have a development prospect. It is very meaningful in theoretical and actual areas to find methods for selecting high yield, quality micro-algae and improving biomass and oil content of micro-algae, because the content of useful substances from wild micro-algae can’t meet the commercial requirements, UV and laser mutagenesis are useful methods for inheritance breeding, which have played an important role in breeding of economic micro-algae and brought encouraging achievements, however, the research about UV and laser mutagenesis on the breeding of micro-algae for energy has never been reported.In this research, we selected Nannochloropsis YW0980as experiment material, based on the studying on biological effect of UV and laser irradiating micro-algae. Complex mutagenesis of UV and laser were used to improve the quality of algae, meanwhile, fluorescence analyzing method; conventional biophysical and biochemical method were used to collect high oil algae. It is studied on improving the biomass and oil content of micro-algae by optimizing the condition of culture to explore a new culture method. This research provides a new method and idea for collecting high oil micro-algae. The main research contents and results including1、 The content of crude oil and fatty acid of six wild micro-algae were analysed by gas chromatography. Nannochloropsis YW0980with high oil and reasonable fatty acid composition was selected as experiment material for further research.2、 The biological effect of the micro-algae was studied by two kinds of lasers. It was shown that the growth rate and oil content of the micro-algae were significantly improved by CO2-laser (wave length10.6μm, power10w,light beam length74cm,dose30s、60s).The content of oil was improved at136.60%-172.16%compared with control group. The physiology was also improved under different degrees by semiconductor-laser(wave length:440nm, power:150mw, dose:10min、20min、30min), however, the effect of semiconductor-laser was not as obvious as that of CO2-laser3、Two mutants (N27and N63) with better physiological and biochemical index were selected by repeatedly screening with different doses of UV-mutagenesis. their growth rate were improved by41.9％、26.1%compared with initial algae., extracellular polysaccharide was also improved by38.57%and19.68%respectively, however, the content of their proteins were decreased after mutagenesis. The content of oil and total polysaccharide of N63mutant was improved, while the content of N27was decreased.4n Based on the above studies, N27and N63were continued to be irradiated by CO2-laser. The results showed that the physiological activity of strains irradiated by UV could be promoted by laser, result in lag phase shorted and life cycle extended. The content of pigment、polysaccharide、 protein and oil was increased with different degrees under the irradiation of CO2-laser(30s and60s). The content of protein and oil of N27and N63was improved by28.38%-68.76%and17.36%-31.62%compared with control group.5、The condition of culture of mutants with high oil selected by UV-laser were optimized. The results showed:it was better for the growth of mutants under the condition of enough nutrients and better for oil accumulation when the culture was shot of N or P. Uniform design was used in optimization of media to get a kind of condition of culture(the concentration of NaNO3was65mg/L、 the concentration of NaH2PO4was2mg/L、 the concentration of MgSO4was0.5mg/L) which was better for the growth of mutant、 the accumulation of protein and oil. |
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