为了提高枯草芽孢杆菌生长和产孢效率,在30 L发酵罐水平考察了苹果酸对菌株DF生长代谢的影响.发酵16~27 h耦合pH 8.0流加苹果酸(终质量分数1.5%)使得生物量(22 h)达到3.68× 1010 CFU/mL,较对照提高71.9%;同时,芽孢数为3.63×1010CFU/mL,较对照提高92.1%.转录组差异分析表明:苹果酸强化了菌株DF糖异生途径、磷酸戊糖途径(pckA、fbaA、zwf上调0.38~1.51倍)、三羧酸循环(citZ上调2.10倍)的代谢效率;降低了细胞氧化胁迫强度(丙酮酸氧化酶编码基因poxL下调72.9%、硫氧还蛋白还原酶编码基因trxA上调2.88倍,19~24h的H2O2浓度下降了45.9%~51.3%);增强了Spo0A的磷酸化效率(kipL、rapAD、abrB下调57.5%~75.9%;clpX、phrCF、spo0B、sigA上调0.73~12.76倍),显著提高菌株DF的生长及芽孢形成效率.本研究可为枯草芽孢杆菌工业化高效发酵生产提供理论支撑.
To improve the growth and sporulation efficiency of Bacillus subtilis,the effect of malate on the cell growth and metabolism of B.subtilis DF was investigated in a 30 L bioreactor.At 22 h of fermentation,a biomass of 3.68 × 1010 CFU/mL was obtained by malate addition to a final concentration of 1.5%during 16-27 h after the pH reached 8.0 at 16 h,which was 71.9%higher than that of the control group.Meanwhile,the number of spores was 3.63 × 1010 CFU/mL,which was 92.1%higher than that of the control group.Differential transcriptomic analysis showed that malate increased the metabolic efficiency of the gluconeogenesis and pentose phosphate pathways with 1.38 to 2.51-fold up-regulation of the zwf,pckA and fbaA genes,respectively and the metabolic efficiency of the tricarboxylic acid(TCA)cycle with 3.10-fold up-regulation of the citZ gene,reduced cellular oxidative stress with a 72.9%down-regulation of the poxL gene,a 3.88-fold up-regulation of the trxA gene,and thus a 45.9%-51.3%reduction in H2O2 concentration during 19-24 h,and enhanced the phosphorylation efficiency of Spo0A with down-regulation of the kipL,rapAD and abrB genes by 57.5%-75.9%,and up-regulation of the clpX,phrCF,spo0B and sigA genes by 1.73-13.76 folds,significantly improving the growth and sporulation efficiency of B.subtilis DF.These findings provide theoretical supports for the industrial application of B.subtilis.