Abstract
It has been often observed that bacteria seemingly adapt to sucrose monoesters of fatty acids, which are supposed to be effective nontoxic antimicrobial agents. In the present experiment, effects of the esters on the germination, outgrowth and vegetative growth of Bacillus cereus were investigated with reference to the adaptation phenomenon. The esters showed inhibitory effect on the development of spores into multiplying cells by preventing outgrowth, in the order of effectiveness of lauryl ester>palmityl ester>stearyl ester. However, the cells of which growth had been once inhibited again developed in the medium. This resumption of growth occurred almost in parallel to a decrease in the concentration of the esters in the medium. Vegetative growth of cells was also prevented by the addition of esters, but the growthinhibited cells again recovered their ability to grow during further incubation in the medium. Furthermore, it was found that esterase is released from germinated spores and growing cells. Taken together, the results indicated that the loss of antimicrobial activity of the esters observed during cultivation is due to the decomposition of the esters by esterase.
