Abstract
Welan gum is an exopolysaccharide produced by Alcaligenes facalis NX-3. The composition of the medium for the production of welan gum was optimized with a stepwise strategy. Effects of various carbon and nitrogen sources were investigated. Plackett–Burman design was applied to elucidate the key ingredients in the media and the results indicated that the corn starch, cottonseed cake flour have significant effects on welan gum production. Central composite design was employed to search for the optimal concentration of the two key components and the experimental results were fitted to a secondorder polynomial model at a 98% level of significance. By solving the regression equation and also by analyzing the response surface contour plots, the relative high welan gum production (22.85 g l -1 ) was obtained at the optimal medium combinations and fermentation conditions as corn starch 43.6 g l -1 , cottonseed cake flour 4.1 g l -1 , 16-h-old inoculum of 3% (v v -1 ) sizes, initial pH 7.0 and temperature 30 o C. These predicted values were also verified by validation experiments.
Highlights
Welan gum is an exopolysaccharide produced by bacterium with many attractive properties
Plackett–Burman design was applied to elucidate the key ingredients in the media and the results indicated that the corn starch, cottonseed cake flour have significant effects on welan gum production
As shown in Figure 1(A), the maximum biomass (5.8 g l-1), the broth viscosity (11000 cp), and the synthesis of welan gum (19.1 g l-1) were observed when corn starch served as the carbon source, followed by sucrose and glucose
Summary
Welan gum is an exopolysaccharide produced by bacterium with many attractive properties. It is composed of tetrasaccharide repeating units of D-glucose, Lrhamnose and D-glucuronic acid with L-rhamnopyranosyl or L-mannosyl as the side chains (Kumar et al, 1996). Due to its excellent rheological properties, welan gum is used in many applications, mainly for concrete additives and enhanced oil recovery (E.O.R.) (Sébastien et al, 1999; Lachemi et al, 2004). It has been several years since welan gum was first discovered, the process for the production has not been thoroughly studied.
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