The Research On Fermentation Technology For Lipid Rich In Palmitic Acid And Its Biodiesel Preparation

With the aggravation of energy crisis and environmental pollution worldwide, every country in the world has been spurred to search for renewable energy. Biodiesel has become more attractive recently because of its environmental benefits. However, the feedstock of biodiesel cannot satisfy even a small fraction of the demand, the high cost of feedstock becomes the main hurdle to the commercialization of biodiesel. Microorganism is a promising feedstock of biodiesel for its short life cycle, high cell density, high lipid content and so on which is a kind of promise biodiesel feedstock.In this research, a sequential optimization of fermentation culture conditions for Schizochytrium sp. S056 rich in palmitic acid(PA) were researched to improve the PA yield, and analysis and evaluation of its lipid to prepare biodiesel were done, and the main results were as follows:( 1) The fermentation culture conditions for Schizochytrium sp. S056 were Optimized. First via single-factor test, the culture conditions were optimized, and the best results were initial pH 6.0, temperature 32°C, and critical dissolved oxygen for strain growing of 3%~10%(50 mL broth's volume in 250 mL shake flasks). Then, via single- factor test, confirmed that the best cheap carbon source and nitrogen source were cassava starch and yeast extract(YE) coupled with soybean meal(SM), respectively. And based on response surface method, the optimal medium was obtained with(g/L): cassava starch(hydrolysate) 122.2, YE 10.0, SM 7.0, KH2PO4 1.5, MgSO4?7H2O 0.5, NaNO3 3.0, Na2SO4 3.3. Under the optimum conditions, the maximum yield of PA of 25.95 ± 0.11 g/L has an increase of 76.65% compa red to original fermentation medium.(2) The high cell culture method for Schizochytrium sp. S056 was studied by flask. As a result, the best fed strategy was feeding 40 g/L glucose at 72 th hour, the dry cell weight, lipid production and palmitic acid yield were up to 63.69 ± 0.64 g/L, 46.02 ± 0.66 g/L, 30.42 ± 0.88 g/L, respectively.(3) The potential of lipid as biodiesel feedstock was analyzed by some predictor formula and national standard methods. The most value of each property met the standard, which showed that it can be used as biodiesel feedstock or additive of diesel.(4) Via acid and alkali two-step catalytic transesterification to prepare biodiesel, the conversion rate of 87.34 ± 3.72%. And in order to improve the resistance to oxidation of biodiesel, investigated the effects of different antioxidants and different amount of antioxidant on stability of biodiesel, the results show that 0.3% THBQ can improve stability of biodiesel to meet national standard.