Use of a Nisin-Producing Starter Culture Suitable for Cheddar Cheese Manufacture

A nisin-producing starter culture that produced acid at rates suitable for Cheddar cheese manufacture was developed by combining the naturally occurring lactose-fermenting, nisin-producing, and proteinase-positive strain Lactococcus lactis ssp. lactis NCDO 1404 and the lactose-positive, nisin-positive, proteinase-positive transconjugant Lactococ- cus lactis ssp. cremoris JS 102. Cheddar cheese manufactured with 1% NCDO 1404 and .5% JS102 as starter cultures exhibited normal acid development; the cheese was of normal composition and contained ca. 700 IU of nisin/g. Experiments using a nisin resistance factor from plasmid pFGO10 to increase resistance to nisin by L. lactis ssp. lactis C2 revealed that nisin resistance and acid development by the recipient increased in the presence of nisin. However, the mechanism of resistance encoded by pFGOlO resulted in inactivation of nisin in the test system.