琼脂-孔洞扩散法测定物质抑菌活性中相关影响因素的探讨

Study on the Related Factors of Antimicrobial Activity by Agar-Hole Diffusion Method

以肉桂醛、索氏和超声波提取的肉桂油为试样,讨论样品加入量、浓度、打孔直径及评价指标对琼脂-孔洞扩散法测定物质抑菌活性的影响。结果表明:抑菌活性与样品加入量和浓度都呈正相关,9,11mm孔径的加液量分别为50~70μL和70~90μL比较适宜,应用2倍或3倍梯度稀释法可进行定量分析,较快找到被测物质对供试菌种的最小抑菌浓度。采用样品抑菌圈直径与空白抑菌圈直径的差值作为抑菌活性的评价指标比抑制率更加合理。GC-MS分析表明:索氏和超声波提取的肉桂油主要成分都是肉桂醛,含量分别为60.93%和37.86%。肉桂醛的抑制活性好于索氏和超声波提取的肉桂油,说明肉桂醛也是肉桂油的主要抗菌成分之一。肉桂醛、索氏和超声波提取的肉桂油均对细菌的抑制作用最强,其次是酵母,对霉菌的抑制作用较弱,但浓度为333.33mg/mL的3种试样对黑曲霉的抑制率分别为60.00%,52.63%和47.06%,展现了一定的抑菌效果。肉桂油作为天然植物源抗菌剂用于食品保鲜领域具有一定的参考价值。

The effects of sample additive amount, sample concentration, pore size and evaluation index on the antimicrobial activity of substances by agar-hole diffusion method are discussed in the paper using cinnamaldehyde,soxhlet and ultrasonic cinnamon extracts as materials. The results reveal that the antimicrobial activity is positively correlated with the amount and concentration of samples, and the appropriate additive amount of samples is 50-70 μL for 9 mm pore size and 70-90 μL for 11 mm pore size respectively. Moreover, 9. or 3 times gradient dilution method could be used for quantitative analysis to quickly find the minimum inhibitory concentration of the tested substances against the tested strains. In addition, it is more reasonable to use the difference between the inhibition zone diameter of the sample and the control than the inhibition rate as the evaluation index for determining antimicrobial activity. Cinnamaldehyde is the major component in cinnamon oil identified by GC-MS, and the content is 60.93 for soxhlet extract and 37. 86% for ultrasonic extract respectively. Cinnamalaenyde shows antimicrobial activity than soxhlet and ultrasonic extracts, which indicates that cinnamaldehyde is also one of the predominant antibacterial components in cinnamon oil. Cinnamaldehyde, soxhlet and ultrasonic cinnamon extracts all show the strongest inhibitory effect on bacteria, followed by yeast and the inhion of mold is weaker, however, the inhibitory rates against Aspergillus niger are 60. 00%, 52.63% and 47.06% for the above three samples respectively at a concentration of 333. 33 mg/mL, which shows a degree of inhibitory effect against the tested mold. It could be concluded that cinnamon oil could be explored as a good source of natural compound with significant antimicrohial activity for the development of food preservation.