Influence of complex nutrients, temperature and pH on bacteriocin production by Lactobacillus sakei CCUG 42687

The effects of process conditions and growth kinetics on the production of the bacteriocin sakacin P by Lactobacillus sakei CCUG 42687 have been studi ed in pH-controlled fermentations. The fermentations could be divided into phases based on the growth kinetics, phase one being a short period of expo nential growth, and three subsequent ones being phases of with decreasing s pecific growth rate. Sakacin P production was maximal at 20 degrees C. At h igher temperatures (25-30 degrees C) the production ceased at lower cell ma sses, when less glucose was consumed, resulting in much lower sakacin P con centrations. With similar media and pH, the maximum sakacin P concentration at 20 degrees C was seven times higher than that at 30 degrees C. The grow th rate increased with increasing concentrations of yeast extract, and the maximum concentration and specific production rate of sakacin P increased c oncomitantly. Increasing tryptone concentrations also had a positive influe nce upon sakacin P production, though the effect was significantly lower th an that of yeast extract. The maximum sakacin P concentration obtained in t his study was 20.5 mg l(-1). On the basis of the growth and production kine tics, possible metabolic regulation of bacteriocin synthesis is discussed, e.g. the effects of availability of essential amino acids, other nutrients, and energy.