Derivation of efficient nisin producers by fusing protoplasts of two allied strains of Lactococcus lactis subsp. lactis with low nisin-synthesizing abilities

摘要

Efficient nisin producers were derived by fusing the protoplasts of two allied strains 729, Lactococcus lactis subsp, lactis and 1605, with low nisin-synthesizing abilities. Conditions promoting protoplast formation, fusion, and regeneration were elaborated. The process of protoplast fusion was studied by electron microscopy. Some physiological and biochemical properties of the parent strains were preliminarily studied to develop selective media suitable for selecting the required clones. The effect of various selective agents in regeneration medium on the segregation of recombinant clones was studied with respect to nisin production. The most potent producers of nisin were 10 to 14 times more efficient than the parent strains.