Efficient xanthan gum production from phosphoric acid–pretreated Cedar wood and Elm wood

Cedar and Elm woods were investigated for the microbial production of xanthan gum using a commercial strain of Xanthomonas campestris. However, the yields of xanthan gum from untreated woods were inefficient. Thus, a dilute phosphoric acid (1-2% w/v) pretreatment at elevated temperatures (140-180 °C) for 10-20 min and concentrated phosphoric acid (85% w/v) pretreatment at 60 °C for 1-3 h were applied to increase production yields. Concentrated acid pretreatment resulted in the highest yields of 9.9 and 10.4 g xanthan gum per 100 g of raw Cedar and Elm wood, respec-tively, whereas the untreated woods yielded 2.0 and 2.4 g xanthan gum per 100 g of raw woods. The dilute acid pretreatment was not as efficient as the concentrated acid pretreatment, it resulted in 4.2 and 5.2 g xanthan gum per 100 g of Cedar and Elm respectively. Consequently, the woods are suitable substrates for xanthan gum production after pretreatment with concentrated phosphoric acid at 160 °C for 1 h. The quality of produced xanthan gum was also compared with a commercial xanthan gum using Fourier transform infrared spectroscopy, and the results indicated that the produced xanthan gum was similar to the commercial product. Although the pretreat-ments presented in this study increased the xanthan gum yield up to fourfold, it was at the expense of increasing pretreatment costs. This research provides the basis for the economic analysis required for the commercial implementation of these pretreatments.