TECHNOLOGY FOCUS - BIOLOGY - Preferred Method: The usage of the microbe to be fermented in the microbial oil and biodiesel preparation comprises: (i) adding cassava starch to tap water, mixing to obtain a starch slurry, adjusting the pH of the slurry, adding alpha -amylase to the slurry, liquefying at a suitable temperature to obtain a starch liquefied liquid, adjusting the pH of the starch liquefied liquid, adding a saccharifying enzyme to obtain a starch saccharified liquid and measuring the concentration of the reducing sugar, (ii) transferring and activating the oil producing saccharomycetes in a slant-surface culture medium, culturing the seed in a seed culturing medium, transferring 5-15% of the strain to the fermenting culture medium, culturing for 36-72 hours at 25-35 degrees C and rotating at 300-500 revolutions/minute and measuring the biological content of the strain after fermentation, (iii) fermenting the microbe to obtain a great number of thallus, centrifuging the thallus, drying and collecting, using petroleum ether as an organic solvent with a sorbitic extractor, heating in a water bath at 60-90 degrees C, reflowing for 6-10 hours to extract the oil from the thallus and (iv) taking the microbial oil (5-10 g), alcohol (1-3 g) which is used as an esterification agent, an alkali (1-10 wt.% of the microbial oil), which is used as a catalyst, reacting for 0.5-5 hours at 30-100 degrees C, performing trans-esterification reaction, separating to obtain a fatty acid methyl ester, which is the biodiesel with glycerine as a by-product. The cassava starch treatment comprises: (a) adding cassava starch to tap water in a mass ratio of 1:1-6, preferably 1:4 mixing to obtain a starch slurry, (b) adjusting the pH of the slurry at 5-7, preferably 5.5-6, adding 1-10 units/g, preferably 2-6 units/g starch dry weight of alpha -amylase to the slurry, liquefying for 1-3 hours at 80-100 degrees C to obtain the starch liquefied liquid, (c) adjusting the pH of the starch liquefied liquid at 3.5-6, adding 100-1000 units/g starch dry weight of saccharifying enzyme, preferably 200-400 units/g, adjusting the pH at 4-5, saccharifying for 0.5-3 hours at 50-70 degrees C to obtain the starch saccharified liquid, and (d) measuring the concentration of the reducing sugar which is 100-300 g/l and using the cassava starch saccharified liquid as a carbon source for fermenting the culture medium. The strain of the microbe-fermented oil is Trichosporon cutaneum B3 which has a preservation number CCTCC NO.M 2010076 and is mutagenized and bred in the laboratory. The fermenting process comprises: (p) inoculating the fresh oil producing strain on the slant surface to the liquid seed culture medium and culturing for 20-30 hours at 28-30 degrees C and 150-200 revolutions per minute, and (q) grafting cassava starch saccharified liquid (5-15%) as the carbon source to the fermenting culture medium, culturing for 36-72 hours at 25-35 degrees C and rotating at a speed of 300-500 revolutions/minute, fermenting with a ventilation amount of 0.5-1.5 volume of air per volume per minute to obtain the thallus with microbial oil, controlling the squirm pump flow in connection with a fermenting pot, adding 0.5-3 M of sodium hydroxide or 1-3 M of phosphoric acid to adjust the pH to 5.5-6.5 and sterilizing each culture medium for 20 minutes at 115 degrees C. The trans-esterification reaction has different temperature and time parameter ranges based on the catalyst. Preferred Components: The culture medium comprises (in g/l): glucose (70), ammonium nitrate (0.5), yeast extract powder (1), magnesium sulfate (0.4), monopotassium phosphate (0.75) and calcium chloride dihydrate (0.4) of pH 6.The fermenting culture medium comprises (in g/l): cassava starch saccharified liquid (30-100) as the carbon source in terms of amount of glucose, ammonium nitrate (0.5), yeast extract powder (3), magnesium sulfate (0.4), monopotassium phosphate (0.75) and calcium chloride dihydrate (0.4) with a pH of 5.5-6.5. The catalyst for trans-esterification reaction of the microbial oil to prepare the biodiesel comprises an acid, an alkali, a solid alkali or a biological lipase, e.g. Novozym 435 (RTM: Immobilized Candida antarctica lipase B).