巴氏醋酸杆菌对发酵中醋酸胁迫的生理应答

Physiological response to acetic acid stress of Acetobacter pasteuranus during vinegar fermentation

摘要:

摘要:【目的】研究Acetobacter pasteurianus CICIM B7003 对醋酸发酵形成的酸胁迫环境在细胞形态、生理、代谢方面的响应，初步提出巴氏醋杆菌的动态耐酸机制模型，为高酸度高强度液态深层醋酸发酵提供理论帮助。【方法】在9 L自吸式发酵罐中用A.pasteurianus CICIM B7003发酵醋酸，选取不同生长阶段细胞检测其荚膜多糖含量、膜不饱和脂肪酸含量、耐酸基因转录水平、乙醇呼吸链酶和ATP酶活性，研究醋酸菌形态、生理和代谢随醋酸积累的变化。【结果】醋酸的存在能减少细胞分泌荚膜多糖，发酵中多糖占细胞干重百分比由最初2.5%下降到0.89%;随发酵进行细胞膜不饱和脂肪酸占膜总脂肪酸含量显著提高，致使细胞膜流动性增加;耐酸基因相对转录水平显著提高而提升了细胞对酸性环境的抗性;乙醇呼吸链酶和ATP 酶活性随醋酸积累也显著提高，为细胞提供足够的能量以满足耐酸机制对能量的需求。【结论】初步确定A.pasteurianus CICIM B7003主要依靠改变细胞膜脂肪酸组分、激活耐酸基因转录、增强乙醇呼吸链活力及快速产能等机制的协同作用，实现对酸胁迫的制衡。

Abstract:

Abstract:［Objective］The aim of the study is to propose a dynamic acetic acid resistance mechanism through analysis on response of cellular morphology，physiology and metabolism of A．pasteurianus CICIM B7003 during vinegar fermentation．［Methods］Vinegar fermentation was carried out in a Frings 9 L acetator by strain B7003 and cultures were sampled at different cellular growth phases．Simultaneously，percentage of capsular polysaccharide versus dry cells weight，ratio of unsaturated fatty acids to saturated fatty acids，transcription of acetic acid resistance genes，activity of alcohol respiratory chain enzymes and ATPase were detected for these samples to assay the responses of bacterial morphology，physiology and metabolism．［Results］ When acetic acid was existed，no obvious capsular polysaccharide was secreted by cells．As vinegar fermentation proceeding，percentage of capsular polysaccharide versus dry cells weight was reduced from 2.5% to 0.89%．Ratio of unsaturated fatty acids to saturated fatty acids was increased obviously which can improve membrane fluidity．Also transcription level of acetic acid resistance genes was promoted． Interestingly，activity of alcohol respiratory chain and ATPase was not inhibited but promoted obviously with acetic acid accumulation which could provide enough energy for acetic acid resistance mechanism．［Conclusion］On the basis of the results obtained from the experiment，A．pasteurianus CICIM B7003 relies mainly on the cooperation of changes of extracellular capsular polysaccharide and membrane fatty acids，activation of acid resistance genes transcription，enhancement of activity of alcohol respiratory chain and rapid energy production to tolerate acidic environment．