Synthesis of glycerol monolaurate by direct esterification and its antibacterial activity against Staphylococcus aureus
Choosing lauric acid and glycerol as raw materials and p-toluene sulfonic acid as a catalyst,the effects of reaction temperature,reaction time,stirring speed,raw material molar ratio and catalyst dosage on the puri-ty of glycerol monolaurate(GML)were determined through single factor test.And the inhibitory effect of GML concentration and pH value changes on Staphylococcus aureus were studied.The results showed that the high-est purity of GML was obtained under the conditions of n(glycerol)∶n(lauric acid)=3∶1,reaction tempera-ture of 180 ℃,reaction time of 3.5 h,stirring speed of 250 r/min,and p-toluenesulfonic acid dosage of 0.4 wt％.This process was the optimal synthesis process.The orthogonal experimental test showed that the syn-thesis temperature had the greatest impact on the purity of GML.The initial purity of GML prepared under the optimal synthesis process was 47.7％,and the purity after purification could reach 97.2％.The antibacterial per-formance test showed that the inhibitory effect of GML on Staphylococcus aureus was positively correlated with its concentration.When the concentration reached 12 mg/mL,the diameter of the antibacterial zone reached its maximum value of 16.1 mm.The antibacterial rates of GML against Staphylococcus aureus gradually decreased with time.Under pH values of 5.7 and 7.2,the half-lives of GML against Staphylococcus aureus were 54 and 49 hours,respectively.It can be seen that under weak acid conditions,GML has a longer antibacterial half-life and better antibacterial effect on Staphylococcus aureus.
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