Handbook of Meat Processing

Starter Cultures for Meat Fermentation 203

with other Gram - positive cocci, such as

Micrococcus genus, because these two genera

often cohabit the same habitats. However,

molecular taxonomy has revealed that these

genera are phylogenetically separate and dis-

tinct. The genus Staphylococcus belongs to

the Clostridium subdivision of Gram - positive

bacteria, while Micrococcus is part of the

Actinomycetales ., Kocuria varians (formerly

classifi ed as Micrococcus varians ), is a

member of the Micrococcaceae family, and

is used in meat starter cultures for its nitrate

reductase ability.

The genus Staphylococcus comprises

41 validly described species and subspecies

of Gram - positive, catalase - positive cocci

(Ghebremedhin et al. 2008 ; Bannerman

2003 ; Kwok and Chow 2003 ; Spergser et al.

2003 ), 10 of which contain subdivisions with

subspecies designations (Place et al. 2003 ;

Spergser et al. 2003 ; Garrity et al. 2004 ). The

staphylococci present a spherical shape, and

the cells are often grouped to form clusters.

These microorganisms are widespread in

nature; their major habitats are skin, skin

glands, and the mucous membranes of

mammals and birds. Some species, mainly

coagulase - negative staphylococci (CNS)

such as Staphylococcus xylosus , S. carnosus ,

S. equorum , and S. saprophyticus , are

frequently isolated from dry fermented

sausages, but other species occur, too.

Staphylococci are facultative anaerobes

capable of metabolizing a number of differ-

ent sugars. Under anaerobic conditions, the

major end product is lactic acid, but acetate,

piruvate, and acetoin are also formed.

Since S. xylosus and S. carnosus are

highly competitive in meat fermentation,

present important technological properties,

and generally lack virulence determinants,

these are the most common CNS species

used as starter cultures. These organisms

show the ability to survive under environ-

mental stress, such as high salt and low

temperatures encountered during meat fer-

mentation. CNS primarily contribute to the

largest of the Lactobacillus genus. Although,
L. curvatus is frequently isolated from meat
fermentations and has a role in the control of
undesirable bacteria due to the production of
antimicrobial peptides (see Chapter 14 ), less
information on its physiology and genetics is
available.
Pediococci, although they do not compose
a relevant part of the microbial community
of European fermented sausages, occasion-
ally occur in small amounts (Papamanoli et
al. 2003 ). They are more common in fer-
mented sausages from the United States,
where they are intentionally added as starter
cultures to accelerate acidifi cation of the
meat batter. Pediococci are Gram - positive,
coccus - shaped lactic acid bacteria, showing
the distinctive characteristic of tetrad forma-
tion via cell division in two perpendicular
directions on a single plane. Pediococci is
a typical example of a rapid fermentative
organism, with a higher optimum growth
temperature requirement, and of homo-
fermentative lactate production during
sausage fermentation (Axelsson 2004 ).
Phylogenetically Pediococcus species belong
to the L. casein - Pediococcus sub - cluster of
the Lactobacillus cluster. The genus consists
currently of nine species, but only P. pento-
saceus is generally used as a starter culture
for meat fermentation. The species P. cerevi-
siae , frequently mentioned as a starter culture,
has now been reclassifi ed as P. pentosaceus.
The genome - sequencing project of P. pento-
saceus ATCC 25745 is complete ( http://
genome.jgi-psf.org/draft_microbes/pedpe/
pedpe.info.html ).

Gram - Positive Catalase - Positive Cocci

( GCC +)

Micrococcaceae were frequently mentioned
as components of meat starter cultures,
but this term generally referred to members
of the Staphylococcus genus (which
belongs to the family Staphylococcaceae).
Staphylococcus were originally grouped