Optimization and economics of Xanthan gum production from coconut water

Coconut water (CW), with all its complex and highly variable composition, was confirmed to support quality xanthan gum production. The critical nutrients involved in the process were found present in CW at favorable amounts. Glucose, which inhibits xanthan gum production at concentrations higher than 5 percent was present at lower levels, hence, refined sugar supplementation was found necessary to significantly increase the production. CW supplemented with refined sugar up to 5 percent hexose level (RS5) can produce an average of 20-25 g xanthan/L compared to synthetic medium (Roseiro et.al., 1992) fermentation which produces an average of 12 g xanthan/L. RS5-derived xanthan gum was determined comparable to commercial xanthan gum in terms of its viscosity (in solution), in glucose content, and pyruvic acid content. Nitrogen supplementation was unnecessary to increase yield, although, it apparently confers increase in the viscosity of the product. Mineral supplementation was demonstrated to have minimal effect on yield and quality of xanthan gum produced which implies that these may already be present in CW at concentrations sufficient to support production. Except for Zn 2+ which gave a significant increase in viscosity, xanthan yield and quality remained unaffected by BO3 3- or Fe 3+ addition. PO4 3- and Mg 2+ supplementation tend to lower both production and viscosity at increasing concentration. Sulfate supplementation led to a very high xanthan yield (27-71.5 g/L) which was non-viscous. Baffled flask fermentation did not significantly increase yield but gave higher xanthan viscosity. Inoculum level of 11.25 percent and 3 to-day fermentation duration was found optimal for producing quality xanthan from coconut water. Prolonging the fermentation rendered a slight increase in yield but seemed to lower the viscosity of the xanthan produced. Under optimized fermentation condition, a product yield coefficient of 0.72 was achieved. A liter of RS5 which could produce 20-25 g/L xanthan was estimated to cost Ph P3.55 which is 3.7 times cheaper than chemically defined medium designed for xanthan gum production