Study On The Production Of Welan Gum By Microbial Fermentation

Welan gum（named S-130）is a kind of soluble extracellular polysaccharide produced by Sphingomonas sp.In an aerobic submerged fermentation.It is composed of tetrasacharide repeating units include of consists of laevoglucose,levorotatory glucose hyaluronic acid and L-rhamnose with L-mannosyl or L-rhamnopyranosyl as the side chains.Welan gum is one of the most market prospective microbial polysaccharide developed after xanthan gum and gellen gum by Kelco（a company of American）which has excellent rheological properties in aqueous media.Its special molecular structure and excellent rheological properties has attracted the extensive attention of food,oil exploitation and building industry.In this study,based on Sphingomonas sp.511 which preserved in our laboratory,we explored the factors which can influence welan gum fermentation.The welan gum fermentation media and production process conditions are optimized.The optimized fermentation media are:glucose 35.5g/L,soybean meal powder 6.2g/L,K₂HPO₄ 2.4g/L,MgSO₄ 0.3g/L.The optimized conditions are:the seed age of 15hour,inoculum amount of 10%（v/v）,80mL working volume in 500mL flask,pH 8.0,shaking speed of 300rpm,fermentation temperature of 32℃and fermentation cycle 72h.On the basis,we examined the solid-liquid ratio,extraction time,extraction temperature,extraction pH,volume of alkali addition and the method for the welan gum extraction.The experiments show that:Welan gum can get higher extraction yield at the condition of solid-liquid ratio 3.5:1,extraction time for 30 min and room temperature.When adding alkaline in the fermented liquid reached 0.15 mol/L（pH 13）,the consumption of alcohol is lowest which was only 1.5 times as the size of fermented liquid.The status and appearance of the product is the best.The way by using extrusion or jet to scatter the fermented liquid into the method of extracting solvent system,can greatly reduce the use of alcohol,safety and easy to operation.We explored the shearing force,temperature,pH,salt and the concentration of welan gum solution on the influence of solution viscosity about our welan gum products.The exploration show that:welan gum solution is a pseudoplastic fluid,have good shear thinning properties,heat-resistant,acid and alkali resistant and salt resistance.