Abstract

When attempting to improve production of nisin, understanding the effect of non-nutritional factors is essential owing to a lack of adequate information about these factors among various investigations. In order to assess some of non-nutritional factors and how they influence the nisin production in batch cultivation, a laboratory scale study was performed. Lactococcus lactis subsp. lactis ATCC 11454 produced nisin and Micrococcus luteus ATCC 10240 was used in bioassay measurement as the nisin-sensitive strain. The age and size of inoculum, initial pH value of the medium and flask volume/medium volume (F/M) ratio, temperature as well as agitation were studied by changing one factor at a time while keeping others constant in de Man, Rogosa and Sharpe (MRS) medium. Our results implied that pH value was positively related to increase nisin production. Two other important factors for a maximum nisin production were found to be agitation and flask volume/medium volume (F/M) ratio. Inoculum size more than 2.5% (v/v) had no effect on nisin production. The most suitable condition for inoculum age was 32-hour-old culture (at the end of log phase) and 27°C temperature provided maximum nisin production.

Key words: Nisin, Lactococcus lactis, temperature, bioassay, batch fermentation.