In all, 4379 isolates from 35 products, including 24 artisanal cheeses, were
surveyed with a view to identifying strains that could be used as starters in
commercial dairy fermentations. Of the isolates, 38% were classified as
Lactococcus,
17% as Enterococcus, 14% as Streptococcus thermophilus,
12% as mesophilic
Lactobacillus, 10% as Leuconostoc and 9% as thermophilic
Lactobacillus. Acid
production by the isolates varied considerably. Of the 1582 isolates of
Lactococcus
and 482 isolates of mesophilic Lactobacillus tested, only 8 and
2% respectively
produced sufficient acid to lower the pH of milk to <5·3 in 6 h
at 30°C. In contrast,
53, 32 and 13% of Str. thermophilus, thermophilic Lactobacillus
and Enterococcus
isolates respectively reduced the pH to 5·3. These isolates were
found only in some
French, Italian and Greek cheeses. Bacteriocins were produced by 11% of the 2257
isolates tested and 26 of them produced broad-spectrum bacteriocins which inhibited
at least eight of the ten target strains used, which included lactic acid bacteria,
clostridia and Listeria innocua. The most proteolytic of the 2469
isolates tested were
Str. thermophilus from Fontina cheese followed by Enterococcus
from Fiore Sardo and
Toma cheese and thermophilic Lactobacillus from all sources.
Exopolysaccharides
were produced by 5·3% of the 2224 isolates tested.
Partial characterization of probiotic lactic acid bacteria isolated from Chinese dairy products
