Abstract:
Nitrous acid was used to modify traditional de Mann, Rogosa, Sharpe media to
evaluate if the addition of sodium nitrite to MRS media could improve the culturing and
recovery of various lactic acid bacteria species. Yogurt, cheese, and sauerkraut were
inoculated with individual bacterial species followed by the recovery and enumeration of
the species using the pour plate method to compare the sensitivity between nitrous acid
modified MRS (mMRS) and traditional MRS. Lactobacillus delbrueckii and Lactobacillus
bulgaricus were recovered at significantly higher counts from cheese in nitrous acid
mMRS than MRS while there was no significant difference for other species and food
systems. Growth curves were also generated for multiple lactic acid bacteria as well as
nonstarters in both mMRS and MRS to measure the selectivity of nitrous acid mMRS.
All lactic acid bacterial species along with Bacillus cereus and Bifidobacterium longum
grew to significantly higher densities in nitrous acid mMRS than MRS while there was
no significant difference in the density of Enterococcus faecalis. It was determined that
nitrous acid mMRS is a viable alternative media for the culturing of various lactic acid
bacteria.
