Agriculture Reference
In-Depth Information
bound of 39 000 for bovine lactoferrin (Aisen and Leibman 1972). Its proposed
mode of action is iron deprivation of the target microorganism resulting in a
predominantly stasis effect although cidal effects have also been reported (Arnold
et al.
1977). These have not confi rmed by other workers (Rainhard 1987;
Gutteberg
et al.
1990), who demonstrated an inhibitory effect. Lactoferrin from
bovine milk was fi rst isolated by Groves (1960). Various methods for the isolation
of lactoferrin from bovine milk are described including gel fi ltration (Butler
1973), dialysis followed by chromatographic separation (Tsuji
et al.
1989),
affi nity chromatography on sepharose columns (Arnold
et al.
1977; Schimizaki
and Nishio 1991), affi nity chromatography with heparin cross-linked columns
(Blackberg and Hernell 1980) and affi nity chromatography on DNA agarose
columns (Hutchens
et al.
1989).
Lactoferrin is commercially available both as liquid and dry preparations.
In the last 30 years it has been used in East Asia in several infant formulae
because of its metal chelating activity (Satué-Gracia
et al.
2000). There is
also interest in lactoferrin and lactoferricin (see below) for treatment of diseases
of freshwater and sea water species of farmed fi sh (Kakuta 2000) and shrimp
(Koshio
et al.
2000). Lactoferrin has also been shown to be effective in meat
products (Al-Nabusi
et al.
2006; Al-Nabusi and Holley 2007; Del Olmo
et al.
2009). It has recently received approval for application on beef in the US (USDA/
FSIS 2008).
Partial peptide hydrolysis of human and bovine lactoferrin produces the active
peptide, lactoferricin (Jones
et al.
1994; Tomita
et al.
1994). Lactoferricin shows
a marked antimicrobial activity and, in most cases, is more effective than
lactoferrin. It is active against a wide range of Gram-positive and Gram-negative
bacteria (Murdock
et al.
2007) and fungi and parasites (Naidu 2000b).
6.3.3 Lysozyme
Since its discovery by Alexander Fleming in 1922 (Fleming 1922), lysozyme
(
β
-1, 4-
N
-acetyl-muramidase) has been found in many mammals, birds, fi sh,
insects and viruses. The lysozyme from these different sources has a somewhat
different structure and activity (Losso
et al.
2000; Roller and Board 2003).
Lysozyme lyses the cells of Gram-positive bacteria by hydrolysing the
β
-1,
4-linkage between
N
-acetylmuramic acid (NAM) and
N
-acetyl-glucosamine
(NAG) of large polymers (NAM-NAG)
n
of the peptidoglycan component of the
cell wall. Activity against Gram-negative bacteria is none or much lower and
there is no activity against yeasts and fungi.
The most abundant source of lysozyme is hen eggs where it is present at a
level of 3 mg/g. It is extracted on a commercial scale using cation exchange
chromatography (Li-Chan
et al.
1986; Scott
et al.
1987; Losso
et al.
2000).
Recombinant DNA technology and protein engineering have been used in attempts
to reduce production costs. The genes encoding for hen egg lysozyme have been
transferred to
Aspergillus niger, E. coli
and
Saccharomyces cerevisiae
. However,
yields have been low at 2-12 mg/l (Miki
et al.
1987; Archer
et al.
1990).
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