THE EFFECT OF VARIOUS CITRUS WASTE FRACTIONS ON XANTHAN FERMENTATION

Four different media of citrus waste origin were compared as substrate s for xanthan fermentation: whole citrus waste, pectic, hemicellulosic and cellulosic extracts. It was found that Xanthomonas campestris uti lized in parallel both simple and complex carbon compounds originating from citrus wastes. The substrate utilization rate in the medium base d on pectic extract was similar to that in the medium based on whole c itrus waste. In addition, pectic extract of citrus waste yielded the s ame amount of xanthan as whole citrus waste. This indicates that water soluble substances in citrus waste such as pectins, organic acids and simple carbohydrates are readily converted into xanthan and that thei r contribution to xanthan production is higher than that of the other constituents of citrus waste. The biodegradability of the hemicellulos e and cellulose extracts of citrus waste was found to be much fewer th an that of the pectic extract. Substrate utilization and its conversio n to xanthan in the hemicellulosic extract was 36% lower, and in the c ellulosic extract 60% lower, than those in the whole citrus waste.