Preparation Of Yeast Extracellular Polysaccharide And Test Of Feeding Sea Cucumber

Marine microorganisms are widely distributed in the ocean.Marine microorganisms are in the surroundings of low nutrition, low temperature, high salt, and high pressure.So they are generally able to secrete new polysaccharides with special structure and function.Extracellular polysaccharide is a kind of polysaccharides which secretes to the bacterial surface.The secretion of yeast polysaccharide contains extracellular polysaccharide. The role of yeast polysaccharide has anti-bacterial, anti-viral and anti-oxidation, even inhibiting tumor.It also has a series of physiological activity.It makes a great contribution to enhance immunity.In addition,it is easy for the extracellular polysaccharide of yeasts to separate from the bacteria.So in recent years, the development and application of this kind of product is developing rapidly, the researchers also show a high degree of enthusiasm and favor.This experiment is based on the yeast Candidaguilliermondi which was isolated from the intestine of thesea cucumber.The fermentation culture was treated with ethanol and Sevag reagent to obtain the crude extracellular polysaccharide. Using the phenol-sulfuric acid method and Coomassie blue method, the purity and protein content of the polysaccharide were measured.The results showed that the purity of the crude polysaccharide is 23.33% and the protein content is 1.29%.To optimize the culture medium component of C.guilliermondi producing the sugar, the method of single factor and orthogonal experiment was done. The optimal result is as glucose25 g/L, peptone 25 g/L, potassium dihydrogen phosphate 2.5 g/L, p H7.0. At this condition,the polysaccharide production is 0.128 g/L, which is increased by 12.4% than before optimization.This study was mainly focused on using the crude sugar purified from the fermentation culture of C.guilliermondi to feed young sea cucumbers for observing their growth and measuring a series of enzymes related to sea cucumber immunity. The feeding cycle was 90 d, and the activity analysis of six enzymes in sea cucumber tissuewas done every 15 d.As a result, the sea cucumber weight was increased by 1.76 fold. The increase of the polyphenol oxidaseactivity is 60.29%, and the highest level is 63.06u/ml in 90 day.The increase of the catalase activity is 72.38%, and the highest level is 18.96u/ml in 45 day. The increase ofthe superoxide dismutaseactivity is 31.43%, and the highest level is 56.89u/ml in 30 day.The increase of the acid phosphatase activity is 23.69%, and the highest level is 50.07u/ml in 90 day.The increase of the alkaline phosphatase activity is 27.44%, and the highest level is19.55u/ml in 75 day.The increase of the lysozyme activity is 32.49%, and the highest level is107.18u/ml in 45 day.By the trial of feeding young sea cucumberswith the yeast extracellular polysaccharide as feed additives, it is confirmed that the growth of sea cucumbers could be promoted and the immune activity of sea cucumbers could be improved. Therefore, it has potential value of furtureresearch and application.