Production of bacteriocin jenseniin G by Propionibacterium is pH sensitive

Bacteriocin jenseniin G is detected typically in 50-fold concentrated 10 d cultures of the producer, Propionibacterium thoenii (jensenii) P126 at low concentrations (32-64 AU ml(-1)). The effect of pH on production was examin ed by growing the producer in sodium lactate broth, both statically and in stirred fermenters, with or without pH control. Activity was detected in un concentrated static producer cultures at day 7 through to day 14. Maximal j enseniin G activity (21 AU ml(-1)) was observed in concentrated supernates at day 9, remaining relatively constant through to day 14. Producer culture s grown in stirred fermenters without pH control yielded detectable activit y in 50-fold concentrated supernates at day 3 and maximal activity at day 1 1. Producer growth in stirred fermenters at controlled pH yielded maximum p roduction at pH 6.40 and maximum activity (160 AU ml(-1)) at day 13. Jensen iin G activity at pH 6.40 represented a fivefold increase over previous rep orts. Medium pH was critical to jenseniin G production.