These plates were incubated at 30 ◦C for 24 h and examined for the presence of 2mmor larger clear zones of inhibition. Arbitrary units (AU) permL (AU/mL) were calculated as the reciprocal of the highest dilution, in a 5 μL amount, which gave a clear zone of growth inhibition on a lawn of sensitive cells (Pucci and others 1988; Bhunia and others 1991). AU/mL of the nisin preparation was calculated to be 320 AU/mg dry material. The amount of Nisaplin required to give the desired 1000 AU/mg of nisin was calculated to be 0.3125 g of Nisaplin/liter.
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