Research And Development For Feed Of Schizochytrium Sp.

The marine fungus Schizochytrium sp.is an oil-producing microorganism whose oil is rich in polyunsaturated fatty acids,which can supplement the fatty acid components lacking in the feeding objects,enhance their immunity and promote biological growth.At the same time,Schizochytrium sp.is fast-growing and is suitable for industrial fermentation production.In this paper,the strain Schizochytrium sp.DP-16 was used to optimize its culture medium and prepare the preparation for feed.Research and development of fungal powder for the preparation of feed,biomass is an important indicator of its evaluation.The Schizochytrium sp.DP-16 medium was optimized by single factor optimization and orthogonal experiments to increase its biomass.First,the single factor test of carbon source,nitrogen source and exogenous additive was used to select glycerol as carbon source,yeast dip powder as nitrogen source,citric acid and sodium glutamate as external additive,and orthogonal test of L₉（3⁴）was designed.Through the orthogonal test results,the optimal ratio of four substances was determined:glycerol 80 g·L^-1,yeast dipping powder 10 g·L^-1,sodium glutamate 15 g·L^-1,citric acid 0.6 g·L^-1.The fungus were cultured in an optimal medium to obtain a biomass of 54.0 g·L^-1,which was 35%higher than that obtained by culturing the medium.The fungal powder is prepared by centrifugation of the gungus and the fungus with the addition of glycerol as a protective agent by vacuum freeze-drying.The results showed that the fungal powder without protective agent and freeze-dried fungal powder with protective agent had the same morphology,both were powder solid,the whole was brown and yellow,with a little fishy smell,but the yield of fungal powder with protective agent was low.At the same time,the fatty acid composition of the fungi and the two fungal powders before freeze-drying were analyzed by gas chromatography-mass spectrometry（GC-MS）.The basic components of the three fungi were the same,and the percentages of the components were approximately the same.The saturated fatty acids are mainly C14:0,C15:0,C16:0 and C17:0,and the unsaturated fatty acids are mainly DPA and DHA.Therefore,it was confirmed that vacuum freeze-drying does not affect the fatty acid composition of the oil produced by the fermentation of Schizochytrium,and the fungi are freeze-dried to obtain a powdery solid with good morphology and can be put into the feed as a fungal powder additive.