[Effect of the initial pH value of the medium on the growth of Streptococcus lactis and the biosynthesis of nisin].

The effect of the initial pH value of the medium within 4.0 to 6.6 on the growth of Str. lactis and biosynthesis of nicin was studied. It was found that at the initial pH 4.0--4.5 of the medium the growth of the culture was poor, i.e. 11--14% of the control (initiral pH 6.6). With an increase in the value of the initial pH at least to 5.0 the growth of Str. lactis also increased. At the initial pH 4.0 no biosynthesis of nicin was observed. Under the experimental conditions the antibiotic synthesis by tr. lactic started at the initial pH being equal to 4.5 and reached its maximum at pH 6.6.