| The results for selecting optimum culture medium and condition for the growth of photosynthetic bacteria, Rhodopseudomonas capsulatus, to enhance carotenoid productivity, can be expected in this thesis. Then carotenoid was extracted and purified. The results are as follows: 1) The optimum medium for producing carotenoid consists of sodium citrate 3.9 g, ammonium chloride 0.4 g, Potassium dihydrogen phosphate (MKP) 1.36 g, yeast extract 0.1 g, ferrous sulfate 9 mg and Magnesium Sulfate Anhydrous 0.3 g in distilled water to 1000ml, pH 6.0; The optimum culture condition is that fermentation substrate was kept still in 35 ℃and 500 lx. Under the optimum culture condition, the yield of carotenoids was increased from 0.49 mg per gram wet cell to 1.05 mg per gram wet cell, and six kinds of component for culturing Rhodopseudomonas capsulatus was saved. 2) The higher carotenoids yield can be obtained by using ultrasonication than utilizing acid and heat or alkali and heat to disrupt cells. The optimum ultrasonication condition is that the wet cells suspended in extraction solvent [acetone: methanol (8:1) (v/v)] were treated with ultrasonic waves (200w) for 4 minutes, then kept in the dark for 1 h. 3) The optimum extraction procedure is as follows: the equal volume of 10 % sodium hydroxide-methanol solution (w/v) and the supernatant obtained by centrifuging the disrupted cell solution was mixed for saponification, then the same volume of light petroleum compared to disrupted cell solution was added to mixture to extract pigment after the mixture was shaked and kept in dark for 2-3 minutes. Distilled water was added to the mixture for the better separation between light petroleum and water. After discarding lower raffinate, light petroleum solution was washed by using distilled water until the lower raffinate is clear. 4) The separation of carotenoids: Five components were purified to be homologous by means of alumina chromatography column. The wave length of maximum absorbance (λmax) of five carotenoid is 470.2 nm, 481 nm, 491.6 nm, 470.8 nm, and 482.2 nm, respectively. With reference to data published, the fraction with 491.6 nm λmax is supposed to be monodemethylated spirilloxanthin and / or spirilloxanthin, which covers 13.7% of total pigment. The component with 470.8 nm λmax is supposed to be lycopene, which covers 32.5% of total pigment. The component with 482.2 nm λmax is supposed to be 3,4 –dehydrorhodopin, anhydro-rhodovibrin, rhodovibrin for the likewise of wave length shape, which covers 38.5% of total pigment. The components with 470.2 nm and 481 nmλmax is still unknown, which covers 4.5% and 8.0% of total pigment, respectively. 5) The pigments are easily dissolved in light petroleum, hexane, chloroform, and dissolved in ethyl acetate, while partly in methanol; Heat has less effect on the stability of carotenoids from Rhodopseudomonas capsulatus, but the pigments kept at high temperature for long time will be destroyed; The pigments are sensitive to lighting, so they should be kept in dark. A lot of metal ions, such as Fe3+ ,Fe2+,Zn2+,Mg2+,Cu2+,Ca2+,Al3+, can cause destruction of carotenoids except K+,Na+, that is why we should avoid using metal vessel during extraction and usage; The pigments show better stability in weak acid, weak base, oxidant and reducing reagent.
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