Phenotypic and molecular characterization of Lactococcus lactis from milk and plants.
OBJECTIVE
The aim of this study was to obtain new Lactococcus lactis strains from nondairy materials for use as milk fermentation starters. The genetic and phenotypic traits of the obtained strains were characterized and compared with those of L. lactis strains derived from milk. It was confirmed that the plant-derived bacteria could be used as milk fermentation starters.


RESULTS
About 2600 lactic acid bacteria were subjected to screening for L. lactis with species-specific PCR. Specific DNA amplification was observed in 106 isolates. Forty-one strains were selected, including 30 strains of milk-derived and 11 of plant-derived, and their phenotypic traits and genetic profiles were determined. The plant-derived strains showed tolerance for high salt concentration and high pH value, and fermented many more kinds of carbohydrates than the milk-derived strains. There were no remarkable differences in the profiles of enzymes, such as lipases, peptidases and phosphatases. Isolates were investigated by cluster analysis based on randomly amplified polymorphic DNA profiles. There were no significant differences between isolates from milk and those from plant. The L. lactis subsp. cremoris strains were clustered into two distinct groups, one composed of the strains having the typical cremoris phenotype and the other composed of strains having a phenotype similar to subsp. lactis. Fermented milk manufactured using the plant-derived strains were not inferior in flavour to that manufactured using the milk-derived strains.


CONCLUSIONS
Plant-derived L. lactis strains are genetically close to milk-derived strains but have various additional capabilities, such as the ability to ferment many additional kinds of carbohydrates and greater stress-tolerance compared with the milk-derived strains.


CONCLUSIONS
The lactic acid bacteria obtained from plants in this study may be applicable for use in the dairy product industry.
Nomura
M
M
Department of Animal Products Research, National Institute of Livestock and Grassland Science, Ikenodai, Tsukuba, Japan. nomura@affrc.go.jp
Kobayashi
M
M
Narita
T
T
Kimoto-Nira
H
H
Okamoto
T
T
D000818:Animals; D015373:Bacterial Typing Techniques; D001483:Base Sequence; D050260:Carbohydrate Metabolism; D002611:Cheese; D005285:Fermentation; D019649:Food Industry; D005516:Food Microbiology; D005838:Genotype; D006801:Humans; D013294:Lactococcus lactis / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D008892:Milk / Q000382:microbiology*; D008969:Molecular Sequence Data; D010641:Phenotype; D010944:Plants / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000379:methods; D019936:Probiotics / Q000302:isolation & purification*; D012336:RNA, Ribosomal, 16S / Q000032:analysis / Q000235:genetics; D019105:Random Amplified Polymorphic DNA Technique
D012336:RNA, Ribosomal, 16S