Study On Prouduction And Application Of Feed Colorant By Rhodotorula Sp. From Farm And Sideline Products Through Solid-State Fermentation

Agricultural and sideline products were chosed as test materials, and Rhodotorula sp. D as fermenting fungi, the solid-state fermentation technology of carotenoids and application of the fermentation products were studied systematically.Strains preserved in our lab were screened and Rhodotorula sp. D was selected as fermenting fungi. By single factor test,multi-factors and perpendicular test, optimum composition of culture medium were as follows: the ratio of beer′s spent grains, soybean dregs and wheat bran was 1:3:2, 60﹪of initial moisture content, and 2.00 g/L K2HPO4, 0.50g/L MgSO4 added as inorganic salt. The optimal culture conditions were as follows:soybean dregs sieved through a 20 mesh screen ,while other materials used directly ; 20g wet medium in 250ml flask, the age of inoculation 24h, inoculation amount 15%, culture temperature 25℃, pH natural, culture time 96h.Shallow tray fermentation technique was studied. The results showed that bed thickness had a significant effect on the carotenoids of fermentation products and the 4cm bed thickness was the best. The humidity of substrate was another important factor . Glycerol was added as humectant and medium with 6% glycerol had the highest carotenoids yield. Bacterial-infection is the most serious problem in solid-state fermentation of carotenoids. Through the analysis of contamination factors in the solid-state fermentation, relative measures were made to prevent contamination.Drying and storage of the fermentation product were discussed. The effects of hot-air and vacuum drying were compared. At the same temperature, vacuum drying cost shorter time and a less carotenoids loss. Effect of light and air on stability of product was great. Dried culture stored in dark with transparent plastic vacuum bag had less carotenoids loss than with nonvacuum bag. The results of storage under temperature of 4℃, 25℃, 40℃in dark with transparent plastic vacuum bag indicated no significant changes of carotenoids loss.Main nutrition components of the dry medium before and after fermentation was determined. The content of carotenoids increased from 1.1mg/kg to 32mg/kg after fermentation. The content of rough protein, rough fat and rough fibre had no significant change. So the culture can be used as feed additive to enhance yolk color.Feeding trials were conducted to investigate the optimum method and amount of supplementing the production of solid-state fermentation by Rhodotorula sp D. It is proved that the red yeast culture of solid-state fermentation is a good natural yolk pigment and nutritious additive. The mixed feed consisting of 30% wall - broken red yeast culture and 70% common laying feed revealed the best comprehensive effect.