Four different fractions of citrus waste were compared as substrates for xanthan fermentation: whole citrus waste, pectic, hemicellulosic and cellulosic extracts. The whole waste was found to be a good substitute for glucose media for xanthan production. Xanthomonas campestris utilized both simple and complex carbon compounds originating from citrus wastes. Substrate utilization in the medium based on pectin extract was similar to that in the medium based on a whole citrus waste and the pectic extract yielded the same amount of xanthan as the whole waste. This indicated that water-soluble substances in citrus waste such as pectins, organic acids and simple carbohydrates were readily converted into xanthan and that they were the main contributor to xanthan production from the whole waste. The biodegradabilities of the hemicellulose and cellulose extracts were found to be much lower than that of the pectic extract.