Xanthan production by solid state fermentation

Xanthomonas campestris strains were cultivated on a variety of solid substr ates in order to evaluate their ability to produce the exopolysaccharide xa nthan. The solid substrates used were agro-industry wastes or by-products, including spent malt grains, apple pomace, grape pomace, and citrus peels, which can be obtained at a very low cost. With most substrates, xanthan yie lds were comparable to those obtained from conventional submerged cultivati on. The basic characteristics of the process were studied on solid substrat es prepared by impregnating the inert support (spent malt grains) with a so lution of nutrients. Fermentations were performed on the laboratory scale e ither under static conditions or in rotating cultures. The production condi tions were optimized so as to achieve polymer yields ranging from 32.9 to 5 7.1 g l(-1), as referred to the liquid volume impregnating the various subs trates. The products were analysed by NMR spectroscopy, revealing a composi tion consistent with that of commercial xanthan. (C) 1999 Elsevier Science Ltd. All rights reserved.