转运蛋白提高凝结芽孢杆菌酸耐受性

Using transporter to enhance the acid tolerance of Bacillus coagulans DSM1

摘要:

光学纯乳酸作为可降解生物材料——聚乳酸(polylactic acid,PLA)的前体物质，正在受到广泛关注。乳酸发酵过程中酸性产物的积累会影响菌株的生长，提高菌株酸耐受性具有重要意义。本研究以乳酸生产菌株凝结芽孢杆菌(Bacillus coagulans) DSM1为出发菌株，通过对凝结芽孢杆菌DSM1及其乳酸脱氢酶双敲除菌株(DldhL1DldhL2)进行比较转录分析，筛选酸耐受相关的转运蛋白基因。对关键基因RS16330、RS06895、RS16325、RS10595、RS00500、RS07275、RS10635及RS01930进行实时定量PCR分析，发现基因RS06895、RS10595、RS00500和RS10635在发酵12 h和24 h转录水平显著增强。过表达RS10595基因的菌株，在中性(pH 6.0)条件下生长状况和发酵性能均受到抑制，但在酸性条件下(pH 4.6)，其乳酸生成相比对照组显著提高。上述结果表明，RS10595基因与菌株DSM1的酸耐受性密切相关。本研究有助于进一步探究凝结芽孢杆菌酸耐受的机制，也为构建耐酸菌株提供了基础。

关键词:凝结芽孢杆菌DSM1;乳酸;转运蛋白;比较转录;基因表达

Abstract:

As the precursor of polylactic acid (PLA), optically pure l-lactic acid production is attracting increasing attention. The accumulation of lactic acid during fermentation inhibits strain growth. Therefore, it is necessary to improve the acid tolerance of lactic acid producers. In this study, comparative transcriptomic analysis was performed to investigate the effects of transporters on lactic acid tolerance of Bacillus coagulans DSM1, which is an l-lactic acid producer. The genes with more than two-fold up-regulation in transcriptional profile were further verified using real-time PCR. The transcriptional levels of RS06895, RS10595, RS10595, RS00500, RS00500, RS10635 and RS10635 were enhanced during lactic acid fermentation. Strain overexpressing RS10595 exhibited a retarded cell growth and low lactic acid production at pH 6.0, but an improved lactic acid production at pH 4.6. This study may facilitate the investigation of the acid tolerance mechanism in B. coagulans DSM1, as well as the construction of efficient lactic acid producers.

Key words:Bacillus coagulans DSM1;lactic acid;transporter;comparative transcription;gene expression