Study On The Bacteria/Protein Removal Processes Of Welan Gum

Welan gum,a new kind of extracellular polysaccharide,is produced by Alcaligenes sp.It has excellent properties such as high-stability,shear thinning,thickening,suspensibility and emulsifying.Therefore,welan gum has a potential usage in construction,oil drilling,printing and dying.However,due to the presently extraction techniques,welan gum contains a large number of bacteria and proteins,which limited its application in foods,cosmetics and medicine.Firstly,Sphingomonas sp.WG was used as a strain for the production of welan gum.Centrifugation was tried to remove the bacteria from the fermentation liquor.The relative centrifugal force and dilution times were optimized,but the results showed that centrifugation could not separate the bacteria from welan gum.Then,lysozme was used as the catalyst to decompose the bacteria,and the parameters were optimized.Te optimum process was as follows:the temperature was 40~oC,the pH value was 6.5,the stirring speed was 600 rpm,and the amount of enzyme was 1%.Under such conditions,86.2%of the bacteria in the fermentation could be removed.In addition,the results showed that the preparation process of crude welan gum could remove 40%of the remaining bacteria,so the final bacteria removal rate reached 91.7%.Secondly,the preparation process of raw welan gum was designed and optimized with ethanol as a precipitator.The optimal parameters were:the mixing ratio between fermentation liquor and ethanol was 1:5.5(volume ratio),the precipitator temperature and time were 20~oC and 6 h,respectively.Welan gum precipitation was separated by filtration,and was dried by freeze-drying.Finally,the enzymatic hydrolysis of protein in crude welan gum was optimized by using the single factor method and response surface.The optimum parameters were:the temperature was 49.2~oC,the pH value was 2.45,the enzyme–to-substrate ratio was 4.74%,and stirring speed was 530 rpm.Under such conditions,the protein removal rate reached 95%.