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...
Lactic streptococcal agglutinins are known to promote settling of starter bacteria in milk, resulting in spongy, mealy, shattered curd and sludge formation defects in cottage cheese. These agglutinins are natural antibodies secreted by lactating cows in mature milk in response to infections (mastitis) and in colostrum milk as protective antibodies...
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,...
To determine whether some bacteria are more susceptible
than others to quaternary ammonium compounds, the following bacteria
were grown on agar slants containing various concentrations of
alkyl dimethyl ethyl benzyl ammonium chloride (ADEBAC), and alkyl
dimethyl benzyl ammonium chloride (ADBAC): Aerobacter aerogenes
12658, Alcaligenes metalcaligenes, Brevibacterium linens, Chromobacterium
lividum, Escherichia...
Gram positive cocci isolated from Oregon wines
were characterized and their relative malate fermentation
abilities compared. They were heterofermentative,
catalase negative, and facultatively anaerobic. Glucose,
fructose, cellobiose, maltose, ribose, trehalose, salicin
and esculin were fermented by all strains. Arabinose was
fermented weakly but lactose, raffinose, sucrose, xylose,
rhamnose, mannose and...
Rapid acid production by lactic streptococci used in the manufacture of fermented dairy products is essential to the economy of the
industry and to the public health of consumers.
There remains to
developed, however, an adequate laboratory procedure to detect and
distinguish between slow and fast strains of these bacteria....
This study was carried out to compare the effects of a quaternary
ammonium compound (QAC) upon strains of Pseudomonas aeruginosa
which were either sensitive or resistant to the germicide. The cationic
QAC used was alkyldimethylbenzylammonium chloride. The resistant
types were isolated from the sensitive population by selection
of mutants which...
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...
This study was undertaken to determine the role Leuconostoc
citrovorum may play in carbon dioxide production in milk. The
ability of L. citrovorum strains to produce gas was studied by two
methods. A qualitative method used visual measurement of gas where
an agar plug was forced up the neck of...
Microgard, a commercially-available pasteurized
fermented milk, was found inhibitory to gram negative
bacteria such as Pseudomonas putida, some well-known foodborne
pathogens (e.g. Salmonella, Yersinia and Aeromonas)
and some fungi as revealed by an agar incorporation assay
method. Gram positive bacteria, however, were not
inhibited. Rather, some bacteria in this group...
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...
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...
Lactobacilli are microorganisms with many applications in the
fermented food and dairy industries. In addition to the actual
fermentation of food products, lactobacilli are involved in the
metabolic breakdown of lactose in dairy products, enabling a large
population of lactose-intolerant humans to ingest milk. Lactobacilli
are also used as health...
Two multiple strain lactic streptococcal starter concentrates
were examined to determine whether or not elimination of one of the
three component strains, by addition of its specific phage, resulted
in disproportionate inhibition of acid production (strain dominance).
Both starters showed dominance when tested three to four weeks after
freezing and...
Three commercial sausage starter cultures were grown in
an internal-pH-controlled medium (PHASE 4) and in a soluble
phosphate-buffered medium. The cultures were tested by
comparing viable counts before and after freezing at -40 C
or freeze-drying and subsequent storage for 3 months in the
frozen or dried state. Strains varied...
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...
Dairy leuconostocs are frequently used as aroma-producing bacteria in mesophilic cultures used as starters for milk fermentations. Sixty Leuconostoc strains from different culture collections were studied taxonomically for species identification. Based on morphological, physiological and biochemical tests, twenty of these strains were typed as Leuconostoc mesenteroides ssp. cremoris (Leu. cremoris)....
Pseudomonas aeruginosa cells were selected for their ability
to grow in the presence of 750 ppm alkyldimethylethylbenzyl
ammonium chloride (QAC). These cells were found to retain their
resistance to the germicide throughout tri-weekly transfers for 7
months in tryptone glucose yeast extract (TGY) broth containing no
QAC. Comparisons of the...