植物乳杆菌素plantaricin Q7的合成与降解机制及代谢调控研究

Recently bacteriocins of lactic acid bacteria, as food bio-preservatives, have received enormous attention. However, the amount of synthesis is too low for industrial-scale production. In our previous research, we have selected a strain called Lactobacillus plantarum Q7 which can produce a broad spectrum of bacteriocins. Results indicated that the synthesis of plantaricin Q7 was related to the growth of the strain with a further degradation in the late stage of fermentation. Within this project, we would investigate the transcriptome of L. plantarum Q7 at different growth phase, figure out the synthesis of plantaricin Q7 and corresponding changes in gene expression. The proteome of the strain at different growth phase will be studied with iTRAQ and MALDI-TOF-MS to uncover the relationship between metabolic change and the translation of Plantaricin Q7. The metabolic changes will be analyzed with LC-MS combined with NMR to figure out the synthesis and degradation pathways as well as related key enzymes. The mechanism of the synthesis and degradation of plantaricin Q7 will be revealed at multi-scales from transcription, translation and metabolism which will serve as a theoretical basis for the high expression of plantaricin Q7.

乳酸菌细菌素因其安全、高效成为食品生物防腐剂领域研究热点，但合成量低限制了商业化生产。本课题组前期筛选到产广谱细菌素的Lactobacillus plantarum Q7，确定抗菌成分为植物乳杆菌素plantaricin Q7。研究发现plantaricin Q7合成不但与菌株生长相关，而且发酵后期存在降解现象。本项目拟利用RNA-seq 技术研究L. plantarum Q7不同生长期转录组，明确plantaricin Q7合成相关基因表达变化；采用iTRAQ和MALDI-TOF-MS研究不同生长期蛋白质组，建立代谢变化与plantaricin Q7翻译调控间关系；联合LC-MS与NMR分析代谢产物变化，确定plantaricin Q7合成与降解途径及关键酶，从转录、翻译和代谢水平多尺度揭示plantaricin Q7合成与降解机制，为plantaricin Q7高表达调控提供理论依据。

Plantaricin Q7 是L. plantarum Q7合成的一种广谱型抗菌肽，抗菌效果及生物安全性都很高，但发酵合成产量低。深入开展 plantaricin Q7 的合成调控研究对该广谱抗菌肽的生产和应用具有重要意义。结果表明，本项目利用RNA-Seq技术开展了plantaricin Q7的比较转录组学研究，挖掘plantaricin Q7合成的关键基因groS，从转录水平上揭示了plantaricin Q7合成机制，然后通过调控关键基因表达提高了plantaricin Q7产量；基于代谢组学手段探究了植物乳杆菌 Q7 在不同发酵时间的代谢差异，发现了与plantaricin Q7合成密切相关的丙氨酸，天冬氨酸和谷氨酸代谢，氨基酸生物合成，氨酰-tRNA生物合成和 ABC 转运等差异代谢通路及谷氨酸、谷氨酰胺、5-甲基胞嘧啶等关键代谢物，建立了plantaricin Q7合成代谢模型，为优化plantaricin Q7的合成代谢提供了理论依据；构建了植物乳杆菌素Q7合成差异蛋白表达图谱，发现了休克蛋白GroEL对植物乳杆菌素Q7合成具有促进作用，通过RT-PCR分析结合基因敲除技术，发现了组氨酸蛋白激酶是plantaricin Q7反馈调控的关键蛋白。最后将plantaricin Q7及其产生菌L. plantarum Q7应用到牛乳保鲜和酸奶发酵中，体现出了酸乳辅助发酵剂和生物防腐剂的多重效果，为plantaricin Q7及其产生菌L. plantarum Q7的产业化开发提供了理论依据。