Optimization Of Fermentation Condition For Production Of Carotenoid By Rhodotorula Y-5

Carotenoids are a main kind of widespread natural pigments and are typically seen as pigments in animals, plants and microorganisms. Carotenoids have the function of preventing and curing some diseases, improving the body immunity and delaying senility. Over recent years, there has been considerable interest in the production of carotenoids for their widespread using. It is reported that among the microorganisms that are capable of producing carotenoids, Rhodotorula has great potential in carotenoid production considering its unique advantages, such as simple fermentation conditions, low fermentation cost and short fermentation cycle, easy controlling during the fermentation process and rich nutrition in cells. In this paper, the new Rhodotorula Y-5 screened out and selected through UV was used as the stain to produc carotenoids; the optimal medium composition and the best culture conditions were obtained; the bio-reactor designed by ourselves was used to expand the fermentation; the steam-explosive corncobs was used as the alternative carbon source to produce carotenoids and this provide a reference for the application of producing carotenoids by Rhodotorula and its future industrial production. The results are as follows:1. Based on the single factor test, orthogonal design, response surface experiment, the optimal culture medium for carotenoids production were decided as follows:glucose was 50g/L, peptone was 8g/L, yeast extraction was 10g/L, KH2PO4 was 0.58g/L, MgSO4 was 0.49g/L, NaCl was 0.28g/L, Riboflavin was 2mg/L, tomato juice was 0.75mL/L, soybean oil was 0.6mL/L. And the best shake flask fermentation conditions were as follows:medium volume 25mL/250mL; inoculum size was 10%; rotation speed was 190r/min; initial pH value was 5.0; fermentation temperature was 28℃. Under the optimized conditions, the weight of the dry Rhodotorula Y-5 was 18.57g/L, the production of carotenoid can reach 854.4 lμg/g, and the yield of carotenoids was 15.87mg/L. The yield of carotenoids was increased by 30.4% after optimization.2. The carotenoids fermentation progress with Rhodotorula Y-5 in the 2L bioreactor was also studied. Using the fed-batch culture, the yield of carotenoids was increased by 40.71% compare to the shake flask fermentation progress. The results of continuous carbohydrate supplement technology indicated that:sugar concentration in the fermentation process should be maintained at 20～30g/L, the nitial sugar concentration should not be too high, and the total sugar concentration should be controled less than 60g/L. the optimum aeration rate was also decided at 0.8L/min and the liquid volume was 1500mL. Under these conditions, the production of carotenoids can reach up to 22.33mg/L.3. Enzymatic hydrolysis of steam-explosive corncobs as the carbon source for carotenoids production was also investigated. The fermentation processes for carotenoids production were optimized by a uniform design experiment. The results showed that the highest yield of carotenoids can reach 11.24g/L when the volume charge 23.91 mL in 250 mL flasks, initial pH value was 4.85, inoculum size 9.46%(volume ratio), rotation speed 190r/min, lactoflavin of 2mg/L. This method is firstly reported in china, and the production of carotenoids is comparatively high compared to the experimental data reported in domestic and overseas publications.