PhD Vermeiren Lieve Compleet - Hogeschool Gent

indole and alcohols, which play an important role in the flavour development of dairy
products (Urbach, 1995; Tavaria et al., 2002). Arginine catabolism occurs in most of the
heterofermentative lactobacilli and results in the production of citrulline, ornithine and
ammonia (Kandler & Weiss, 1986; Arena et al. 1999).
1.4. Lactic acid bacteria of importance in food products
In food, LAB contribute to the taste and texture of fermented products and inhibit growth of
bacteria by the production of growth-inhibiting substances. However, LAB are also known to
be involved in spoilage of e.g. beer, wine, meat and meat products and some fish products.
The genera of most importance in the microbial ecology of food products are Lactobacillus,
Pediococcus, Leuconostoc and Lactococcus (Stiles & Holzapfel, 1997; Carr et al., 2002).
1.4.1. The genus Lactococcus
The genus Lactococcus includes several species but Lactococcus lactis is the most important
species of the commercially used LAB. Lactococcus lactis is commonly isolated from plant
material but the most recognised habitat is dairy products. They are non-motile, coccusshaped,
homofermentative bacteria that grow at 10°C and 40°C but not at 45°C, grow in 4%
NaCl and produce L(+)-lactic acid from glucose (Stiles & Holzapfel, 1997; Carr et al., 2002).
The use of lactococci, mainly in the dairy industry (production of cheese or yoghurt), is
widespread and has the longest tradition in industrial starter culture technology. Some strains
of Lc. lactis are also important because of nisin production (Stiles & Holzapfel, 1997).
1.4.2. The genus Leuconostoc
The leuconostocs are heterofermentative cocci that occur in pairs and chains and form D(-)lactic
acid and carbon dioxide from the fermentation of glucose. The leuconostocs require a
less acidic environment (pH ≥ 4,5) than the lactobacilli and the pediococci, which are more
acid tolerant (Carr et al., 2002). Plants are the natural habitat of this genus and
Leuc. mesenteroides subsp. mesenteroides is the principal isolate. In fermented foods of plant
origin, Leuc. mesenteroides is generally the first organism to grow and it is succeeded by the
more acid-tolerant lactobacilli. Leuconostoc mesenteroides, Leuconostoc gelidum and
Leuconostoc carnosum have been isolated from raw and processed meat and meat products
packaged under vacuum or in a modified atmosphere (Stiles & Holzapfel, 1997). Spoilage of
meat products through leuconostocs may be accompanied by the production of slime.
Chapter 1 – Antagonistic micro-organisms for biopreservation of food products 4