Kinetics of butyric acid fermentation of glucose and xylose by Clostridium tyrobutyricum wild type and mutant
Kinetics of butyric acid fermentation of glucose and xylose by Clostridium tyrobutyricum wild type and mutant
复制标题
DOI：
10.1016/j.procbio.2005.10.009
复制
发表时间：
2006-04-01
影响因子：
4.4
通讯作者：
Yang, ST
中科院分区：
文献类型：
--
作者：
Liu, XG;Yang, ST
用野生型ATCC 25755及其突变体PPTA-Em研究了酪丁酸梭菌在pH 6.0和37 ℃下的丁酸发酵动力学，所述突变体PPTA-Em是通过整合诱变以使编码磷酸转乙酰酶（PTA）的染色体pta基因失活而获得的。在游离和固定化细胞发酵中评估了使用该突变体来提高从葡萄糖和木糖生产丁酸的潜力。与野生型相比，在自由细胞发酵中，PPTA-Em从葡萄糖和木糖中产生的丁酸盐增加了15%（0.38 g/g与0.33 g/g），浓度要高得多（葡萄糖为37.2 g/L与22.9 g/L，木糖为33.5 g/L与19.4 g/L）。突变体中丁酸产量的增加可以归因于乙酸产量的减少以及比生长速率的降低。突变体中葡萄糖和木糖的乙酸产量分别降低了13.5%（0.058 g/g对0.067 g/g）和32%（0.045 g/g对0.066 g/g）。突变体在葡萄糖上的比生长速率降低了36%（0.137 h（-1）对0.214 h（-1）），在木糖上的比生长速率降低了26%（0.086 h（-1）对0.116 h（-1））。采用纤维床生物反应器（FBB）培养PPTA-Em突变体细胞，进一步提高丁酸产量。在补料分批发酵中，来自葡萄糖的最终丁酸浓度达到49.9g/L，来自木糖的最终丁酸浓度达到51.6g/L，丁酸产量增加到0.44g/g葡萄糖和0.45g/g木糖。最终产物中丁酸/乙酸比的大幅增加证明，可以得出结论，由于pta基因的敲除，突变体的代谢途径已经转向有利于丁酸的产生，尽管乙酸的产生仍然保持在显着的水平。观察到的代谢转变通过如在二维蛋白质电泳和SDS-PAGE中观察到的改变的蛋白质表达模式证实。(c)2005爱思唯尔有限公司保留所有权利。
The kinetics of butyric acid fermentation by Clostridium tyrobutyricum at pH 6.0 and 37 degrees C were studied with the wild type ATCC 25755 and its mutant PPTA-Em, which was obtained from integrational mutagenesis to inactivate the chromosomal pta gene, encoding phosphotransacetylase (PTA). The potential of using this mutant to improve butyric acid production from glucose and xylose was evaluated in both free and immobilized cell fermentations. Compared to the wild type, in free cell fermentations PPTA-Em produced 15% more butyrate (0.38 g/g versus 0.33 g/g) from both glucose and xylose, at much higher concentrations (37.2 g/L versus 22.9 g/L from glucose and 33.5 g/L versus 19.4 g/L from xylose). The increased butyrate production in the mutant can be attributed to the reduced acetate production as well as reduced specific growth rate. The acetate yield in the mutant was reduced by 13.5% (0.058 g/g versus 0.067 g/g) and 32% (0.045 g/g versus 0.066 g/g) from glucose and xylose, respectively. The mutant's specific growth rate was reduced by 36% (0.137 h(-1) versus 0.214 h(-1)) on glucose and 26% (0.086 h(-1) versus 0.116 h(-1)) on xylose. A fibrous-bed bioreactor (FBB) was used to immobilize PPTA-Em mutant cells and further improve butyric acid production. The final butyric acid concentrations in fed-batch fermentations reached 49.9 g/L from glucose and 51.6 g/L from xylose, with the butyrate yield increased to 0.44 g/g glucose and 0.45 g/g xylose. As evidenced by the greatly increased butyrate/acetate ratio in the final product profile, it is concluded that the mutant's metabolic pathway has been shifted to favor butyrate production due to the knockout of pta gene even though acetate production remains at a significant level. The observed metabolic shift is corroborated by the changed protein expression patterns as seen in two-dimensional protein electrophoresis and SDS-PAGE. (c) 2005 Elsevier Ltd. All rights reserved.