The dairy industry relies primarily on consistent acid production
by the lactic streptococci for the manufacture of certain cheeses
and fermented dairy products. Variation in these cultures due to
genetic exchange has not been thoroughly investigated. This study
was undertaken to determine if genetic homology exists within the lactic
group,...
The public health and economic significance of rapid acid production
by lactic streptococci in controlled dairy fermentations is well
known. However, the fast acid-producing characteristic of these organisms
is not stable, and cultures of fast organisms have been shown
to contain slow cells. These studies were carried out to characterize...
Comparisons were made of the abilities of Streptococcus lactis,
Streptococcus cremoris and Streptococcus diacetilactis bacteriophages
to endure various laboratory isolation and storage treatments.
Neutralization of Cottage cheese whey containing phages offered no
survival advantage over unneutralized samples, refrigeration of
neutral and acid whey samples increased the survival of only the...
This study involved an investigation of lactic streptococci which
had irreversibly lost ability to produce the high levels of acid in milk
necessary during the manufacture of certain fermented dairy products.
The slow acid producing mutants studied were obtained from
a normal acid producing strain by natural selection following induction...
The enzymes and pathways involved in the catabolism of
glucose by several strains of Streptococcus diacetilactis, Streptococcus
cremoris, and Streptococcus lactis, commonly called the
lactic streptococci, were studied. The presence of aldolase,
triosephosphate isomerase and alcohol dehydrogenase in these
organisms provided evidence for the operation of the Embden-Meyerhof-Parnas (EMP) pathway...
A report in the literature suggesting that the use of cottage
cheese dressing cultured with S. diacetilactis would afford enhanced
flavor and shelf life in the finished product prompted this study to
examine reasons for its effectiveness. The method used involved
addition of a culture of S. diacetilactis 18-16 to...
Experiments were carried out to purify and characterize the
galactosidase of the Streptococcus lactis 7962. Purification was
accomplished using standard procedures; however the lability of
the enzyme to numerous treatments limited the techniques that could
be used and the amount of active enzyme recovered. Gel filtration
revealed that the enzyme...
Factors influencing diacetyl production by the aroma bacteria
Leuconostoc citrovorum and Streptococcus diacetilactis were investigated.
When grown in association with lactic streptococci, L. citrovorum
strain 91404 decreased in cell numbers from 10⁸ to 10⁶ over
two weeks of daily subculturing in sterile non-fat milk incubated at
21°C. The ability to...
Trypticase-Soy Broth (TSB) was inoculated with Streptococcus
diacetilactis, incubated at 21C for 24 hours and centrifuged to remove
the cells. When the spent TSB was inoculated with Staphylococcus
aureus, it allowed 99.8% less growth than fresh TSB. If the spent
TSB were supplemented with 0.08 μg/ml of niacinamide, this inhibition...
Fast acid-producing streptomycin-resistant mutants for several
strains of lactic streptococci currently used in commercial Cheddar
cheese manufacture were isolated. Their isolation involved use of a
recently developed differential plating medium that allows identification
of fast acid-producing colonies. Both parents and mutants were characterized
with regard to growth, acid production, proteolytic...
A method for rapid isolation of plasmid DNA from group N
streptococci was developed. Chief advantages of the method were
simplicity, the utilization of microliter quantities of reagents,
and the obtainment of preparations highly enriched for covalently
closed circular plasmid DNA. The method was also applied to over
15 Leuconostoc...