Enzyme and Microbial Technology 39 (2006) 197–207 Review of xanthan gum production from unmodified starches by Xanthomonas comprestris sp. S. Rosalam ∗ , R. England Department of Chemical Engineering, University of Bath, Bath BA2 7AY, UK Received 6 October 2004; received in revised form 19 October 2005; accepted 21 October 2005 Abstract Many attempts were reported to optimise variables in xanthan gum fermentations, i.e. the nutrient composition and feeding technique, temperature, pH, agitation, and adding antifoam. All shows some improvement in the area studied. Other substrates were also tested, such as hydrolysed rice, barley and corn flour, acid whey and sugarcane molasses, etc., but glucose is still the best in-term of the product yield, supply, and the product quality. Sufficient studies of the unstructured kinetics and the structured kinetics models were described in batch processes but the continuous kinetic model is insufficiently cared. Looking at the conventional xanthan production, mixing is the main problem occurred in batch fermentation as the produced broth during the production stage is very viscous, therefore mixing requires considerable balance between cell disruptions and oxygen transfer. Giving the support, e.g. cotton wool and fabric, for microorganisms to adsorb may ensure the nature physical separation between microorganisms and the liquid phase containing nutrients and products. However, the specific xanthan productivity was reported low due to relatively low cell viability. The problem of the limited oxygen transfer suggests that a new bioreactor design is required. The design strategy could be by freely moving of the liquid media and air passing through the porous fibrous matrix, therefore should ensure a good contact between cells that adsorb onto the fibrous matrix support and nutrients. This strategy should improve oxygen transfer, and may increase the reaction rate and reduce the fast growing of mutation. Using ultrafiltration was reported save up to 80% of the energy is required for recovering of xanthan gum. © 2006 Elsevier Inc. All rights reserved. Keywords: Xanthan gum; Xanthamonas campestris sp.; Starch hydrolysis; Glucose 1. Introduction In response to environmental concerns, some industries which have previously used non-degrading polymers in their products and raw materials have looked closely at the possibil- ities of using materials that are “greener” and environmentally friendly. Polymers can be manufactured from petrochemicals, plants, or animals based raw chemicals. Petrochemical based polymers are the less preferable choice compared to biopoly- mers collected or manufactured from plant or animal sources especially for use in consumer products. Despite the increas- ing collection and extraction costs, and volatile market prices of plant and algal gums (biopolymers) it is suggested that the indus- trially produced biopolymers (e.g. modified starches, celluloses, and microbial polysaccharides) could be a suitable alternatives. ∗ Corresponding author. Tel.: +44 1225 865434/384 543; fax: +44 1225 385 713. E-mail addresses: rslamhs@hotmail.com (S. Rosalam), cesre@bath.ac.uk (R. England). Xanthan gum has discovered in the late 1950s by US Sci- entists and is the first biopolymer produced industrially. The natural source of the polysaccharide came from a cabbage plant bacterium, known as Xanthomonas campestris. It was not until 1969 that the FDA issued the final approval for the use of xanthan gum in food products. The demand for xanthan gum produced by Xanthomonas campestris sp. has increased steadily every year and is estimated to grow continuously at an annual rate of 5–10%. Commercial production of xanthan gum uses glu- cose as the substrate, and generally batch production instead of continuous production due to the batch process having been proven to work successfully. However, increasing market price and demand suggests that glucose may no longer economic for the raw material, while using batch processes may also limit the capacity. It is therefore the purpose of this review to investigate alternatives to economically produce xanthan gum. 2. Application of xanthan gum Xanthan gum is widely used in a broad range of indus- tries, such as in foods, toiletries, oil recovery, cosmetics, as 0141-0229/$ – see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.enzmictec.2005.10.019