Rubber-decomposing bacteria produce decomposed rubber waste that thought to be reused for future industrial applications. We attempted to cultivate Lactococcus lactic, which produces nisin, in CMG (complete medium with glucose) medium supplemented with rubber decomposing waste. Rubber decomposing waste promoted nisin productivity but did not promote the growth ability of Lactococcus. Moreover, the hydrophobic fraction of rubber decomposing waste exhibited high nisin-promoting effects. When 1 × 10^-1 fold dilution of CMG medium was used, rubber decomposing waste promoted the growth ability but did not promote nisin productivity.