EFFECT OF VITAMIN-B SUPPLEMENTATION ON LACTIC-ACID PRODUCTION BY LACTOBACILLUS-CASEI

Various nitrogen sources were compared with yeast extract (YE) in term s of their usefulness for efficient lactic acid production by Lactobac illus casei subsp. rhamnosus. None of these nitrogen sources gave lact ic acid concentrations as high as that for YE during 48 h of fermentat ion. On the basis of the amount of B vitamins in YE, various amounts o f five essential B vitamins known to support the growth of L. casei we re supplemented together with the nitrogen sources. The addition of B vitamins at less than 25 mg/l enhanced the lactic acid production to s ome extent in all cases except for the media supplemented with nitroge n sources of casein origin. The most significant increase was obtained with the N-Z-Soy peptone medium, in which the production of lactic ac id after 48 h of fermentation was 2.2-fold higher than that without vi tamin supplementation. Half of the YE in a medium supplemented with 10 g/l YE could be replaced by B vitamins at less than 25 mg/l and 3.3 g /l N-Z-Soy peptone without a significant decrease in the rate of lacti c acid production.