Chemistry Reference
In-Depth Information
808C in the presence of manganese ions. Lactose at 500 g/L yielded 91 g/L
galacto-oligosaccharides in 300 min with 1.5 units enzyme/ml.
Thermus Species
The production of galacto-oligosaccharides has also been explored in strains
of Thermus species. Recombinant production of a thermostable
-glucosi-
dase, expressed in E. coli K 12, has been used to investigate the production of
galacto-oligosaccharides from lactose. The yield of galacto-oligosaccharides
from 300 g/L lactose at 708C was 40% and trisaccharides comprised two-
thirds of the products formed (Akiyama et al., 2001). Choi et al. (2004a) have
also developed a similar method with the production of a recombinant
enzyme from a
-glycosidase in Thermus caldophilus.
5.4.1.4.3
Thermoactinomycetes
Saccharopolyspora rectivirgula
Some thermoactinomycetes have been shown to produce
-galactosidases
which have high
-
D
-galactosyltransferase activity, high heat stability and
which can act in the neutral pH range. Some strains from the genera Sacchar-
opolyspora, Thermomonospora and Thermoactinomyces have been found to
possess effective enzymes. In particular, a strain of S. rectivirgula has been
studied (Nakayama et al., 1992, 1993; Nakao et al., 1994). Nakayama et al.
(1993) pointed out that other
-galactosidases derived from species such as
Paecilomyces variori also possess high heat stability and are capable of
repeated use at high temperatures, but that the Paecilomyces enzyme is not
suitable for many applications because it is effective only at low pH (3.5). The
most advantageous property of the Saccharopolyspora enzyme is its heat
stability over long periods. Nakao et al. (1994) reported a 41% yield of
galacto-oligosaccharides from 1.75 M lactose.
Saccharopolyspora rectivirgula was previously named Faenia rectivir-
gula. Species of Saccharopolyspora are implicated as causal agents of infec-
tion for a condition known as farmer's lung disease. In nature, the species is
found in mouldy hay. It can also cause allergic reactions in humans.
5.4.1.5.
Development of Modified Galacto-oligosaccharide Structures
There is considerable scope for the development of novel galacto-
oligosaccharides with specific functionalities for human health. Oligosac-
charides have been developed to act as alternative receptors to absorb
lectin-like toxins from toxigenic bacteria (VTEC, ETEC, Clostridium difficile)
