bifidocin A是由Bifidobacterium animalis BB04代谢合成的一种新型广谱高效细菌素.为探讨该细菌素的群体感应合成调控行为,本研究通过监测发酵过程中菌体生长及细菌素抑菌活性变化规律,分析菌体密度和细菌素合成的相关性;基于低产细菌素培养模型体系的构建,检测发酵上清液中是否存在群体感应自诱导肽,判断是否存在细菌素合成相关群体感应系统;并通过对发酵上清液中自诱导肽进行提纯和分子质量测定,初步明确其分子特性.结果表明,当菌体细胞达到活菌数为7.31(lg(CFU/mL))时,细菌素才开始合成;发酵过程中,菌体密度与细菌素的合成呈现正相关性;成功构建了低产细菌素培养模型体系,其培养条件为培养温度37?℃、培养基起始pH?5、培养基浓度1/10改良MRS(Man Rogosa Sharpe)培养基、接种量1%、培养时间24?h;基于此模型体系,确定发酵上清液中确实存在可以诱导细菌素合成的自诱导肽,细菌素bifidocin?A的合成是受群体感应系统调控的;通过对发酵上清液进行超滤管筛分、葡聚糖凝胶柱层析及高效液相色谱层析提纯,获得了高纯度自诱导肽样品;采用基质辅助激光解析电离飞行质谱测定其分子质量为3?587.253?Da.%Bifidocin A is a novel bacteriocin produced by Bifidobacterium animalis BB04 with antimicrobial activity against a wide range of foodborne bacteria. The objective of this study was to investigate the quorum-sensing regulation behavior of bifidocin A production in B. animalis BB04. The correlation between cell density and bacteriocin production was analyzed by monitoring the cell growth and bacteriocin antimicrobial activity during the fermentation process. Using a low bacteriocin culture model system, the presence of auto-inducing peptide and quorum-sensing system related to bacteriocin production were analyzed. The auto-inducing peptide was purified by ultrafiltration, Sephadex G25 chromatography and HPLC, and its molecular mass was determined by matrix-assisted laser desorption/ionization time of flight-mass spectrometry (MALDI-TOF-MS). Results showed that bifidocin A began to be synthesized when the cell density reached 7.31 (lg (CFU/mL)), and the bacteriocin production depended on cell density. In the low bacteriocin culture model system, the culture temperature was 37 ℃, the initial pH value of culture medium was 5, the concentration of culture medium was 1/10 modified MRS, the inoculum quantity was 1%, and the incubation time was 24 h. The auto-inducing peptide was detected in the fermentation supernatant and it mediated the regulation of bacteriocin production by the quorum-sensing system. The molecular mass of the purified auto-inducing peptide was 3 587.253 Da.
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