Study On The Production Of Welan Gum By Alcaligenes Sp.

Welan gum is a kind of soluble extracellular polysaccharide produced by Alcaligenes sp. ZW-3 (previously named s-130) in an aerobic submerged fermentation. It is one of the most market prospective microbial polysaccharides developed by Kelco, a company of American. As reported that welan gum in aqueous media has excellent rheological properties, and its special molecular structure has attracted the extensive attention of oil well drilling fluids, building industry and food industry.In this thesis, The effects of different carbon and nitrogen sources and the optimum concentration of other medium components on the quality of fermentation product of welan gum were investigated. In order to reduce environment pollution and protect environment, Two types of fermentation technology of welan gum were studied. The main works and results are as follows:Fermentation evaluation results of welan gum has been redefinited of that the integrated the quality of the product flow characteristics of index n and the apparent viscosity values to ensure that the fermentation products derived from high-quality. The effects of different factors on the quality of fermentation product of welan gum were investigated. The significant factors affecting quality of fermentation product of welan gum as follows: nitrogen sources and phosphate concentration.The effects of pH on the quality of fermentation product of welan gum and phosphate in the role of fermentation were investigated. Use pH control to replace the effect of phosphate in fermentation of welan gum, then concentration of phosphate etc salts as well as nitrogen source for optimal polysaccharide production were carried out, in order to determine the best conditions for new technology of welan fermentation of pH control. The results show that the amount of KH2PO4 and MgSO4?7H2O is reduced by 70 %, 50% compared with the conventional process under the conditions of pH control in the fermentation process of welan. At the same time, using soybean flour as the sole nitrogen resource replace the complex nitrogen source of NaNO3 and beef extract in conventional process. The use of the new technology of welan fermentation with pH control, whether production or rheological properties of products were superior to conventional technology. The primary study of fermentation performance was carried out on 7 L bioreactor, the yield of welan gum was 29.5 g/L, flow characteristics of the product index n value was 0.18, and the viscosity was 9.25 Pa S.In order to reduce wastewater emissions which is generated in the production process of welan gum, preliminary study on circular utilization of distillery wastewater of ethanol which is the main wastewater resource was carried out in this paper. on the basis of major ingredients of distillery wastewater and material consumption, the closed-circuit technology of circular utilization with distillery wastewater was constructed, the purpose of cleaner production was achieved. Research shows that both production and product performance could be basically maintained compared the technology of circulation fermentation with conventional techniques of Welan gum, In addition, the effective components of distillery waste of per cycle were basically identical, the properties of production of circulation fermentation were stability.