Synergist effect of sucrose fatty acid esters on nisin inhibition of Gram-positive bacteria

Nisin in combination with the sucrose fatty acid eaters, sucrose palmitate (P-1570 and P-1670) or sucrose stearate (S-1570 and S-1670) was tested agai nst a range of Gram-negative and Gram-positive bacteria. Initial liquid cul ture investigation showed that the sugar ester P-1670 resulted in a synergi st enhancement of the bacteriostatic activity of nisin against Gram-positiv e bacteria and not Gram-negative bacteria. Some enhancement of the bacteric idal activity of nisin against Listeria monocytogenes was also observed. Th is increased nisin inhibitory effect was confirmed on solid media using pla tes with gradients of pH and NaCl. Synergism was observed with all four suc rose fatty acid esters, which enhanced the antimicrobial activity of nisin against several strains of L. monocytogenes, Bacillus cereus (both cells an d spores), Lactobacillus plantarum and Staphylococcus aureus. The combinati on of nisin and the sucrose fatty acid esters showed no inhibition of Gram- negative bacteria (Salmonella enteritidis, Salm. typhimurium and Pseudomona s aeruginosa).