Xanthan gum is an important natural polysaccharide, which is industrially produced by various strains of Xanthamonas bacteria. In this study, two different types of wood were used for the production of xanthan gum, since the wood wastes are often a mixture of softwoods and hardwoods. Using lignocellulosic materials as a substrate helps to reduce the price of the finished product, besides reducing the environmental concerns. To improve the yield of xanthan production from the wood, pretreatment with dilute and concentrated phosphoric acid was conducted. The dilute acid pretreatment was conducted at high temperatures (140, 160 and 180 ° C) with liquid to solid ratio of 8 to 1 w / w for 10 and 20 min, whereas the concentrated acid treatment was conducted at 60 ° C for 1, 2 and 3 h. The highest amounts of 20 and 22 g per liter sugar were respectively released from cedar wood and elm wood after pretreatment by concentrated phosphoric acid. The highest yields of glucose from the dilute acid pretreated wood were occurred after treatment with 2% phosphoric acid at 160 ° C for 10 min. The compositional analysis showed that the pretreatment with phosphoric acid reduced hemicellulose and lignin and increased the glucan fraction of the samples. The results of FTIR and SEM analyses showed a dramatic drop in crystallinity index and increase in the porosity and surface area available for enzyme, leading to the increased enzymatic hydrolysis efficiency. The sugar solution obtained was used as a source of glucose for xanthan production. Pure glucose was used to compare xanthan production efficiency. The highest xanthan production yield of 4.25 and 5.25 gram were obtained from 100 g of cedar and elm, respectively. The yields were similar to yield from glucose. The results of FTIR analysis of the produced xanthan and commercially available xanthan showed similar properties. Keywords : Xanthan gum, Acid pretreatment, Xanthomonas Campestris , Phosphoric acid, Cedar and Elm
