Physiological Characteristics and Vitamin Requirements of Lactobacilli Isolated from Milk and Cheese

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Abstract
The vitamin requirements and physiological characteristics of 179 strains of lactobacilli isolated from milk and cheese have been studied and their relationship to classification discussed. The vitamin requirements showed good correlation with the results of the physiological and biochemical tests with strains of the subgenus Streptobacterium but the correlation was poor among the beta bacteria. It was not possible to differentiate the physiologically similar Lactobacillus brevis and L. buchneri species by their vitamin requirements. The nutritional data indicated that the species L. plantarum probably consists of more than one variety, and confirmed the reliability of a thiamine requirement as a means of differentiating heterofermentative and homo-fermentative lactobacilli. The nutritional data also proved useful with some strains by verifying their unclassifiable status or by making possible their classification when they could not be identified with certainty on the basis of biochemical tests alone. The nitratase activities of strains of L. casei, L. plantarum, L. brevis, L. buchneri and pediococci were also studied. Four of the L. plantarum and 2 of the L. casei strains were able to reduce nitrate but none of the other species tested showed this characteristic.