The gdh gene encoding membrane-bound glucose dehydrogenase of G oxydans was knocked out to obtain the GDHK strain in our previous study, so the growth inhibition of G. oxydans was relieved with the removal of acidification of the culture medium caused by glucose oxidization on the membrane. In order to lower the biocatalytic cost of using GDHK, the relatively low cost glucose was used as the sole carbon source, and the further studies were firstly focused on the orthogonal optimization of the compositions of the culture medium containing glucose. Based on orthogonal experiments, the composition of glucose-containing culture medium were optimized as follows: glucose 40 g-L"1, yeast powder 20 g-L~ (NH4)2SO4 0.5 g-L"1, KH2PO4 4 g-L"1 and MgSO4-7H2O 0.5 g-L"f. It was found that, when the GDHK strain is cultivated in above optimized culture medium, the cell yield increases 25% from 0.6 g-L'1 to 0.75 g-L"1. In addition, four kinds of resting cells of the GDHK cultivated separately on four commonly used carbon sources were used to oxidize 2,3-butanedioI to acetoin, respectively; and the catalytic experiments show that the catalytic effect of glucose-grown GDHK strain is the best since the acetoin yield arrives 80% with the final concentration of 31.3 g-L"1 which is 13-fold of that of the original G oxydans strain under the same culture conditions, and is 1.2-1.5 times more than that of the GDHK cultured on other medium after 12 h. Meanwhile, the used amount of glucose can be reduced toapproximately half of that when the other carbon sources are used. All of these suggest that the lowering production cost strategy of using glucose as the carbon source to substitute using other polybasic alcohols for GDHK culture in the industrial process of producing acetoin from 2,3-butanediol has a broad prospect of application%在前期的工作中对氧化葡萄糖酸杆菌的膜结合葡萄糖脱氢酶基因(gdh)进行了敲除,已得到一株工程菌株GDHK[1],去除了由于该酶的存在而导致葡萄糖培养基容易酸化的途径,从而促进细胞在葡萄糖上的生长.为了更有效地利用葡萄糖这一相对廉价的碳源、降低氧化葡萄糖酸杆菌的生物催化成本,首先用正交实验方法对GDHK的葡萄糖培养基优化,优化结果显示最优的葡萄糖培养基配方为:葡萄糖40 g·L-1,酵母粉20 g·L-1,硫酸铵0.5g·L-1,磷酸二氢钾4g·L-1,七水硫酸镁0.5g·L-1.用优化好的培养基配方测定GDHK的生长,最终菌浓从0.6g·L-1提高到0.75 g·L-1,提高了25％.其次,实验还探讨了原始菌621H和敲除菌GDHK分别在葡萄糖、山梨醇、甘露醇和甘油这4种碳源培养基上培养所得的静息细胞催化2,3-丁二醇生成乙偶姻的影响.实验表明,在葡萄糖培养基上生长的GDHK得到的静息细胞催化效果最好,反应进行到12h,乙偶姻的转化效率已达到80.00％,浓度为3130 g·L.,是同样在葡萄糖上生长的原始菌细胞催化能力的13倍,同时也是其他培养基的1.2～1.5倍,而葡萄糖的用量也只有传统的其他碳源用量的一半,这些都说明用葡萄糖代替其他多元醇,作为工业上培养氧化葡萄糖酸杆菌催化乙偶姻生产的碳源,降低生产成本的策略具有较好的应用前景.
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