SUMMARY: Stable mutant colonies were picked from a parent strain of which gave improved yields of nisin; further improvement could not be produced by means of eolchicine or camphor.

Nisin is stable in the culture fluid at acid pH values, but is inactivated by Seitz filtration or heating at pH 6 to 9. A ‘nisinase’ was not found.

In the presence of sufficient glucose, growth was increased when the lactic acid formed was neutralized, the concentration of pantothenic acid becoming the limiting factor. Maximum nisin yields were obtained when, during fermentation in the presence of sufficient glucose and pantothenate at 23-30°, the pH was stabilized at c. 6, which is the pH optimum for nisin synthesis.

Sodium lactate and nisin are only slightly inhibitory to the organism. Growth comes to an end because of the maximum limiting population density (‘M’-concentration) of cells, and is not due to the exhaustion of food or accumulation of toxic products.


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