get a pretty bad rap. We give them long, complicated names like
Streptococcus thermophilus, or else we
call them something negative like "germs." But we depend on microorganisms
in every realm of life, from producing the food we eat to cycling
energy in our ecosystems.
Meet Lactobacillus. This friendly microbe
lives just about everywhere, including in dairy products and on
fruits and vegetables. Most types of Lactobacillus
wouldn't hurt a flea (though they might change your milk into yogurt).
We use Lactobacillus to make yogurt,
as well as cheese, buttermilk, soy sauce and kimchee.
is an anaerobe, which means it grows best in environments lacking
oxygen (though it has no trouble living with oxygen; it just slows
When you make kimchee, you set up a very friendly environment for
Lactobacillus by filling a bottle with
cabbage and adding salt, which helps to release water and sugars
from the cabbage cells. By keeping the cabbage submerged in cabbage
juice, you create an anaerobic environment.
This combination of no oxygen and lots of sugar is a paradise for
Lactobacillus, which happens to be quite
fond of sugar. It will happily eat up the sugars and churn out lactic
acid, a habit that gives the microbe its name.
activity is at the heart of kimchee fermentation. The more sugar
Lactobacillus eats, the more lactic acid
it produces, and this is why the pH
of your kimchee drops over time. Lactobacillus
grows best at a pH of about 5. The accompanying chart shows how
pH, glucose (or sugar), and lactic acid all change over time in
There are several species of Lactobacillus,
which fall into two major groups depending on what they produce
after eating sugars. The homofermentative
bacteria produce one thing: lactic acid.