Fundamental Food Microbiology, Third Edition - Fuad Fathir

MICROORGANISMS USED IN FOOD FERMENTATION 131
Group II, depending on the carbohydrates and the amounts available, either produce
mainly lactic acid, or a mixture of lactic, acetic, and formic acids, ethanol, and CO 2.
Group III species ferment carbohydrates to a mixture of lactate, acetate, ethanol,
and CO 2.
The three Lactobacillus delbrueckii subspecies are used in the fermentation of
dairy products, such as some cheeses and yogurt. They grow well at 45ºC and ferment
lactose to produce large amounts of D(–) lactic acid. b-galactosidase in these subspecies
is constitutive. Lab. acidophilus and Lab. reuteri are considered beneficial
intestinal microbes (probiotic) and present in the small intestine. Lab. acidophilus
is used to produce fermented dairy products and also either added to pasteurized
milk or made into tablets and capsules for consumption as probiotics. It metabolizes
lactose, and produces large amounts of D(–)-lactic acid. However, in Lab. acidophilus,
b-galactosidase is generally inducible. Lab. helveticus is used to make some
cheeses and ferment lactose to lactic acid (DL). Lab. casei ssp. casei is used in some
fermented dairy products. It ferments lactose and produces L(+)-lactic acid. Some
strains are also used as probiotic bacteria. Strains of Lab. casei ssp. rhamnosus (also
called Lab. rhamnosus) are now used as a probiotic bacterium. Some strains of Lab.
johnsonii are also used in probiotics. Lab. plantarum is used in vegetable and meat
fermentation. It produces DL-lactic acid. Lab. curvatus and Lab. sake can grow at
low temperatures (2 to 4ºC) and ferment vegetable and meat products. Lab. sake is
used to ferment sake wine. Lab. kefir is important in the fermentation of kefir, an
ethnic fermented sour milk. Lab. sanfrancisco is associated with other microorganisms
in the fermentation of San Francisco sourdough bread. Lab. viridescens, Lab.
curvatus, and Lab sake are associated with spoilage of refrigerated meat products. 2,4
F. Oenococcus
Oen. oeni, previously designated as Leu. oeni, has the general characteristics of
Leuconostoc spp. It is found in the winery environment. It is sometimes used to
accelerate malolactic fermentation in wine. The cells transport malate in wine and
metabolize it to lactic acid and CO 2. This process reduces the acidity of wine.
A. Bifidobacterium
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IV. OTHER STARTER CULTURES
They are morphologically similar to some Lactobacillus spp. and were previously
included in the genus Lactobacillus. The cells are Gram-positive, rods of various
shapes and sizes, present as single cells or in chain of different sizes. They are
nonsporeforming, nonmotile, and anaerobic, although some can tolerate O 2 in the
presence of CO 2. The species grow optimally at 37 to 41ºC, with a growth temperature
range of 25 to 45ºC. They usually do not grow at a pH above 8.0 or below
4.5. They ferment glucose to produce lactic and acetic acid in a 2:3 molar ratio
without producing CO 2, and also ferment lactose, galactose, and some pentoses. 2