以甘油为底物发酵生产新型黄原胶

Production of a New Xanthan Gum with Glycerol as Substrate

经过驯化得到了一株可以利用甘油发酵生产黄原胶的野油菜黄单胞菌突变株,Xanthomonas. campestris WXLB-006。RT-PCR结果显示:X. campestris WXLB-006中甘油代谢相关基因(glpF,glpK,glpD,fbp)的相对表达量均高于原始菌株,依次为glpD (8.53)> glpF(7.64)> glpK(6.61)> fbp(5.79)。初始甘油质量浓度40 g/L、变通气量和变搅拌转速(0~24 h,0.5 vvm和200 r/min;24~60 h,1.0 vvm和400 r/min)以及三阶段变速流加甘油策略(24~34 h,3g/L/h;34~44 h,2 g/L/h;44~54 h,1 g/L/h),使生物量由1.65 g/L增加到1.94 g/L,黄原胶产量由17.8 g/L提高到33.9 g/L,发酵周期由120 h缩短至60 h。重要的是,以甘油为底物发酵得到的黄原胶具有粘度低、透明性高、水化速率快和反复冻融处理粘度增大的特点。

A mutant strain, which was named X. campestris WXLB-006 and could use glycerol for xanthan production,was obtained by adaptive evolution. RT-PCR results showed that the transcriptional level of genes related to glycerol metabolism （gtpF,gtpK,gtpD,and fbp） in X. campestris WXLB-006 was higher than those of the parent strain, and the order of these four genes was gtpD（8.53） 〉 gtpF（7.64） 〉 gtpK（6.61） 〉 fbp （5.79）. With low glycerol concentration（40 g/L）, adoption of variable aeration rate and stirring speed （0 -24 h, 0.5 wm and 200 rpm;24 -60 h, 1.0 vvm and 400 rpm）, and three-stage varied speed feeding glycerol strategy（24-34 h, 3 g/L/h; 34-44 h,2 g/L/h;44-54 h, 1 g/L/h） ,biomass increased from 1.65 g/L to 1.94 g/L and xanthan yield from 17.8 g/L to 33.9 g/L,but fermentation time decreased from 120 h to 60 h. Importantly,xanthan gum produced from glycerol has the properties of low viscosity, high transparency, fast hydration rate, and increased viscosity after treated with -20 ℃ freeze-thaw cycles.