肉桂醛对大肠杆菌和金黄色葡萄球菌的抑菌作用及抑菌机理研究

Mechanism and Antibacterial Activity of Cinnamaldehyde against Escherichia coli and Staphylococcus aureus

研究了肉桂醛对大肠杆菌和金黄色葡萄球菌的抑菌作用及其抑菌机理。本文采用滤纸片扩散法测定抑菌圈大小,双倍稀释法测定最低抑菌浓度、最低杀菌浓度,以此评价肉桂醛对大肠杆菌和金黄色葡萄球菌的抑菌性,通过扫描电镜观察、胞膜通透性、胞膜完整性、膜电位实验,阐述肉桂醛抑菌的机理。结果表明:肉桂醛对大肠杆菌和金黄色葡萄球菌的抑菌圈分别为21.75 mm、29.37mm,最低抑菌浓度均为0.25μL/m L,最低杀菌浓度均为0.5μL/m L;肉桂醛破坏了菌体细胞的形态,出现形变;随着肉桂醛浓度的增大,悬液中相对电导率迅速升高,表明肉桂醛影响细菌的膜通透性,而成倍数增长的核酸、蛋白质含量表示胞膜的完整性遭到破坏,肉桂醛降低菌体膜电位,影响其代谢活性,从而抑制细菌生长。肉桂醛主要作用于细胞膜,适宜作为天然防腐剂,抑制食品中腐败菌和致病菌的生长,延长食品货架期。

The antibacterial activity of cinnamaldehyde against Escherichia coli and Staphylococcus aureus, and the underlying mechanism were evaluated. Antibacterial activity was determined based on the diameter of inhibition zone(DIZ) that was measured by the disc diffusion method, and by the minimum inhibitory concentration(MIC) and minimum bactericidal concentration(MBC), measured to a series of doubling dilutions. Furthermore, the antibacterial mechanism was explored using scanning electron microscopy, cell membrane permeability and integrity, as well as membrane potential. The DIZ values of E. coli and S. aureus were 21.75 mm and 29.37 mm, respectively. The MIC(0.25 μL/m L) and MBC values(0.5 μL/m L) were the same for both bacteria. Scanning electron microscope images showed that the structure of the bacterial cell was damaged by cinnamaldehyde with consequent morphologxical changes. With increasing concentration of cinnamaldehyde, the relative electric conductivity increased rapidly, indicating that the permeability of the cell membrane was affected by cinnamaldehyde. Furthermore, the multi-fold increase in nucleic acids and proteins in the cell suspension revealed that cinnamaldehyde damaged the integrity of the bacterial membrane, decreased the membrane potential, and affected the metabolic activity, thus inhibiting bacterial growth. Cinnamaldehyde exerts its main effect on the bacterial cell membrane, and is suitable as a natural preservative to inhibit the growth of food-spoilage and pathogenic bacteria, thus extending the shelf life of food.