Influence of medium composition on lactic acid production from dried whey by Lactobacillus delbrueckii

The production of lactic acid, lactic acid dehydrogenase (LDH) and single cell protein (SCP) from dried whey by fermentation with Lactobacillus delbrueckii subsp, bulgaricus 369 was investigated. A medium consisting of dried whey and supplements which enabled exponential growth of the organism was developed. Maximum lactic acid production was achieved using enriched whey (8% w/v), at pH 5.5 for 24 h. Addition of yeast extract plus MnCl2 gave the highest production of lactic acid (1.71 g/l.h), specific activity of LDH (1.03 U/mg protein) and SCP (32.8%). In batch culture, the addition of 20 g/l glucose plus 0.75 g N/l, as (NH4)2SO4, achieved the highest enzymatic activity. By contrast, when xylose and cellobiose were used as a source of fermentable carbohydrates all variables were repressed.