Optimization and cost of xanthan gum production from coconut water by Xanthomonas campestris pv. campestris NRRL 1459

Xanthan gum is the microbial exopolysaccharide produced by pure culture fermentation with Xanthomonas species. Because of its unique and desirable rheological properties, it has gained wide-spread utility in many industries; as non-toxic thickener in food, as fracturing and drilling fluid additive in petroleum, as an ingredient for printing pastes in textiles, as a suspending medium for insoluble glaze particles in ceramics, as a component in slurry formulations in explosives, as a polymerization agent for paper/adhesives, and as contact time extender for solvents (Kang and Cortrell, 1979). The cost and fermentation problems prohibit its production in countries such as the Philippines and Mexico. This study is the first attempt to utilize coconut water as substrate to produce xanthan gum. Coconut water (CW) with all its complex and highly variable composition, was found to support quality xanthan gum production by X. campestris pv. campestris NRRL 1459. Supplemented with refined sugar up to 5% hexose level (medium CWS), it could produce an average of 20-25 g xanthan/L, compared to synthetic medium of Roseiro et.al (1992) which produces an average of 12 g xanthan/L. CWS-derived xanthan gum was found comparable to commercial xanthan gum (SIGMA) in terms of viscosity, glucose content, and pyruvic acid content. Nitrogen supplementation was unnecessary to increase yield, although, it seemed to increase the viscosity of the product. Supplementing coconut water with minerals, was found to have minimal effect on yield and quality of xanthan gum produced which implies that these minerals may already be present in CW at concentrations sufficient to support xanthan production. Sulfate supplementation led to a very high xanthan yield (25-71.5 g/L) but the product was found to be non-viscous. Inoculum level of 11.25% (v/v) and 3- to 4- day fermentation period were found optimal for producing quality xanthan from CW. Under optimized fermentation conditions using CWS medium, a product yield coefficient of 0.72 was achieved. A liter of CWS which could produce 20-25 g/L xanthan was estimated to cost PhP 3.55, 3.7 times cheaper than using chemically defined medium designed for xanthan gum production