Study on Antibacterial Properties of Monolaurin and Its Mechanism

Monolaurin is composed of a molecular12the number of carbon atoms with a molecular glycerol. Monolaurin has been widely used in food, medicine, cosmetics and other fields, and monolaurin was found to also have good antibacterial properties, it has a good inhibition of some microorganisms. Antibacterial properties of monolaurin to food microorganism were studied, and the bacteriostatic mechanism of monolaurin to sensitive strains was studied from the cellular and molecular level. These conclusions provide more perfect theory basis for application of monolaurin.The antibacterial properties of monolaurin were studied. Pour plate method, liquid culture method and photoelectric turbidimetric method were used respectively to determine minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and antibacterial aging. Results showed that gram-positive bacteria and fungi were sensitive to monolaurin, which almost had no inhibiting effect to gram-negative bacteria. The minimum inhibitory concentration of monolaurin to staphylococcus aureus, bacillus subtilis, yeast, aspergillus niger and penicillium were0.04mg/mL,0.04mg/mL,0.32mg/mL,0.32mg/mL and0.16mg/mL respectively. The minimum bactericidal concentration of monolaurin to staphylococcus aureus, bacillus subtilis, yeast, aspergillus Niger and penicillium were0.16mg/mL,2.5mg/mL,1.25mg/mL,2.5mg/mL and0.64mg/mL respectively. Bacteriostasis half-life of monolaurin to staphylococcus aureus, yeast and aspergillus Niger were50h,115h and115h respectively. The inhibition rate of monolaurin to bacillus subtilis kept at100%, and it remained at around85%as to penicillium. In addition, the minimum inhibitory concentration and minimum bactericidal concentration of monolaurin were better than that of potassium sorbate and sodium nitrite. The antibacterial aging of monolaurin to bacterium was better than that of potassium sorbate and sodium nitrite, and it was inferior to potassium sorbate and sodium nitrite as for fungi.The antibacterial mechanism of monolaurin was studied. Scanning electron microscopy (SEM) was used to observe bacterial Surface morphology. Leaked amount of intracellular proteins, nucleic acids and ion leakage were determined by spectrophotometric method and conductivity method. Electrophoretic method was used to determine the relative molecular mass of leaked intracellular proteins and nucleic acid, and compared with organic solvent treatment group. Results showed that monolaurin can lead to morphological changes in staphylococcus aureus and bacillus subtilis. The leaked intracellular proteins of monolaurin to staphylococcus aureus, bacillus subtilis, yeast, aspergillus niger and penicillium were13.4μg/mL,32.6μg/mL,38.4μg/mL,26.8μg/mL and18.1μg/mL respectively. The conductivity changes caused by Intracellular leaked ion were20μs/cm,21μs/cm,17μs/cm,160μs/cm,205μs/cm and210μs/cm respectively. The kinds of leaked intracellular protein of gram-positive bacteria caused by monolaurin was different from that caused by suitable concentration of organic solvent, and monolaurin can selectively alter the permeability of bacterial membrane.By studying the following conclusions:Staphylococcus aureus, Bacillus subtilis, Yeast, Aspergillus niger, Penicillium glaucum are sensitive to monolaurin, Escherichia coli is unresponsive to monolaurin. The antibacterial mechanism of monolaurin is through selective permeability change sensitive strain, lead to sensitive strain caused by leakage of intracellular protein and ion.