Enhancement Nisin Activity By Some Natural Additives

Nisin showed great inhibition of gram positive bacteria while it had no effect on gram negative bacteria or yeast.It is clear from the present study that 250ug/ml of nisin was lethal for S .aureus but this dose decreased to 25 ug/ml when combined with 0.05% of citric acid or 0.1% of lactic acid or 0.4% of cinnamon. Although nisin had no effect on P. aeruginosa but when 200ug/ml of nisin combined with 0.2% of citric acid or 0.1% of lactic acid or 2% of cinnamon P. aeruginosa completely inhibited.In the same manner 200ug/ml of nisin was sufficient to inhibit Debaryomyces sp. growth when combined by 3% of citric or 3.5% of lactic or 2% of cinnamon. On the other hand, 25 μg/ml of nisin reduced the following lethal concentrations of S .aureus from0.2% to 0.05%, 0.15% to 0.1% and from 1.2% to 0.4% for citric acid, lactic acid and cinnamon, respectively. While. 200 ug/ml of nisin decreased the following lethal concentrations of P. aeruginosa from 0.3% to 0.2%, 0.3% to 0.1% and from 4% to 2% for citric acid, lactic acid and cinnamon, respectively. Two hundred ug/ml of nisin decreased lethal concentrations of Debaryomyces sp. from4% to 3%, 4.5% to 3.5% for citric acid and lactic acid, respectively. Two hundred ug/ml of nisin did not reduce cinnamon lethal dose.