Antibacterial activities of purified monolaurin obtained from enzymatic glycerolysis of palm kernel olein-stearin blend against Bacillus subtilis

Monolaurin can be produced by enzymatic glycerolysis of a palm kernel olein-stearin mixture. Monolaurin can act as an antibacterial agent against Gram-positive and Gram-negative bacteria. Few studies have investigated activity of monolaurin against Bacillus subtiliscells and spores. Therefore, the aim of this study was to investigate effects of a purified monolaurin from enzymatic glycerolysis of palm kernel olein-stearin mixture on growth, spore germination, cell surface hydrophobicity and cell structure of Bacillus subtilisFNCC 0060.

Monolaurinwas produced using palm kernel-olein mixture under the best enzymatic glycerolysis condition and purified using solvent (hydroalcoholic) method. Effects of a purified monolaurin on Bacillussubtilisgrowth and spore germination were studied using nutrientbroth. Analysis of cell surface hydrophobicity was carried out using microbial adhesion to hydrocarbons assay and cell structure was studied using transmission electron microscope.Completely randomized experimental design was used and each treatment was carried out in triplicate. Analysis of variance and Duncan multiple range tests were used to analyze data.

Results showed that purified monolaurin inhibited growth of Bacillus subtilisFNCC 0060. Moreover, development of Bacillus subtilisin nutrient broth with monolaurin of 100-5,000 μg.ml-1was slower than that without monolaurin.Higher concentration in the media decreased the microbial specific growth rate and increased doubling time. Spores of Bacillus subtilisFNCC 0060 in nutrient broth with monolaurin of 100-1,000 μg.ml-1delayed germination for up to seven days of incubation. Presence of monolaurin significantly decreased bacterial cell adherence. Furthermore, cytoplasm of Bacillus subtilisFNCC 0060 seemed shrunk significantly, causing cytoplasmic damages and disorganization of the components.