Discussion
Our
hypothesis was that we could isolate L. casei
from concentrated organge juice. According to our
research, Lactobacillus casei is a short, gram
positive rod, that can ferment mannitol, is
non-motile, catalase negative, microaerophilic,
and causes a drop in pH when fermenting various sugars. Our results indicated
that we did indeed isolate L. casei and
therefore proved our hypothesis. The Lactobacillus Selection Oxgall Agar that was utilized was not as selective for lactobacillus
as was expected. There was a great deal of contamination of yeast mixed with
our bacteria. It took several days of microscopic examination of our samples
from the streak plates in order for us to get the right colony isolated and
finally obtain a pure culture on our Oxgall plate. In
addition we found it beneficial to use the catalase
test as one of the initial tests to confirm contamination, or lack of
contamination in the culture. Because our contaminants i.e. possible yeast were
showing catalase positive results; therefore, we were
able to use this test in order to verify that our lactobacillus did not
have any catalase positive contaminants. The catalase test was easier to conduct in comparison to the
gram stain and gave faster results as a result we felt that this test was more
efficient to be used earlier on in the isolation process.
As the tests were conducted, it was evident that our
organism had been isolated. All of our tests that were preformed matched the
anticipated results obtained through our research. The results of the various
tests preformed to confirm the isolation of Lactobacillus casei are outlined in the Results
section. The ADT CaCO2 plate gave us a strong indication that we had isolated Lactobacillus.
When this plate is inoculated with Lactobacillus the plate should show
evidence of clearing. Our plate demonstrated clearing therefore confirming we
had isolated Lactobacillus.
Lactobacillus casei is
naturally found in many dairy products, some meats, and in fruits and
vegetables, especially those that are spoiled. This particular species of Lactobacillus
is occasionally referred to as an opportunistic pathogen because it has been
shown to be a contributing factor to problems such as tooth decay in children.
However, this can only occur when other microbes are already present in a biofilm on the teeth.
In addition to its ability to cause food spoilage, Lactobacillus casei is an organism with a great deal of clinical
significance. L. casei can be used for biopreservation of foods because it produces substances
that have antimicrobial activity against a narrow range of both gram positive
and gram negative organisms. Often, L. casei is
used in conjunction with other select microbes as a biopreservative(Encyclopedia
of Food Microbiology). Also, many Lactobacillus species are used in probiotics, however, Lactobacillus casei
“has proven to be significantly better than other Lactobacillus
species with many superior qualities, including excellent adherence to the
intestinal tract”(probiohealth
website). It is critical to be able to effectively isolate Lactobaillus casei
so that it can be an effective probiotic. If a
clinician is going to use this organism to help the normal flora of the
intestinal tract, then it is imperative that the L.casei
probiotic used is free of other microbes that could
cause further distress to the intestinal tract. A clear step by step method of
isolation is important so that we can assure that we have both a pure and
correct culture.