Screening Of High Polyunsaturated-fatty-acids-yield Microbial Strain And Optimize Of Fermentation Conditions

Microbial oil is a new type of oil resources.Due to short growth cycle and contain a variety of fatty acids,oleaginous microorganisms now are widely applied in the biological fuel energy,aquatic feed and feed additives.Some of them,rich in unsaturated fatty acid,are used for improving pregnant women supplements,infant food,etc..It is completely feasible in technology to product microbial oil by zymotechnics.But the key of this way lies in whether there is a suitable microbial source for oil production.So in this paper,Grease microbial was as the research object to find out one kind of microbial for industrialized mass production of unsaturated fatty acids.And then improve the oil production of microbial by mutagenesis and provide a high o1l grease microbial resource.The main research is as follows:(1)According to whether the microbial could compound oil,oil quantity,grease composition and biomass,74 strains of microbial gain from our laboratory were tested.56 strains of bacteria,which compounded o1l well,were filtrated by the Nile red fluorescent staining.And then the microbial were made to test their biomass,oil quantity and grease composition which finally found one strain of microbial,4-Rhodosporidium.sp,that could compound o1l.Among them,4-Rhodosporidium.sp had great biomass which was up to 5.187 g/L.Its oil also had many types of unsaturated fatty acids(30.69%linoleic acid-C18:2 n6c,5.59%gamma linolenic acid-C18:3 n6,1.26%DHA-C22:6 ns,1.6%EPA-C20:5).(2)UV was used to induce A-Rhodosporidium.sp to mutagenesis.Through the sensitivity to UV irradiation time and fatality rate curve,finally select the illumination intensity,70 s induced time and 76.3%fatality rate,for ultraviolet irradiation.And then the survived strains after mutagenesis were used to fermentation processing.After fermentation,through the vanillin dyeing method for rapid detection of microbial oil content,high oil content of mutation strains,4-Rhodosporidium.sp-N07,was found out.(3)In order to improve the oil production efficiency of mutation strain,4-Rhodosporidium.sp-N07,single factor experiment method and response surface method were used to optimize fermentation conditions(temperature,pH,rotate speed,amount of inoculation)for the 4-Rhodosporidium.sp-N07.The results showed that the influence level of four factors for oil content was temperature>rotate speed>pH>inoculation quantity.On the base of the single experiment,the response surface experiment was designed to optimize fermentation,in which oleaginousness was as the response value.Through multiple quadratic regression fitting out of the equation,and the research finally obtained optimal conditions for the fermentation,which was in the condition of temperature?24.09?,pH=6.78,rotate speed?183.66 r/min,inoculation amount=11.75%,the finally oil content of the strain could reach 64.9084%.Under the prediction condition got from the response surface,the verification experiment was come out three times to test the oleaginousness.The result showed that the average oleaginousness in such a fermentation conditions was 61.43%±0.327%,which was close to the predicted value.All of these showed that the response surface experiment can truly reflect the effects of various factors on the 4-Rhodosporidium.s-N07,simulated and forecasted the oleaginousness well,and concluded the best fermentation conditions.