d(GC) - Association of Biotechnology and Pharmacy

Current Trends in Biotechnology and Pharmacy
Vol. 6 (2) 145-165 April 2012, ISSN 0973-8916 (Print), 2230-7303 (Online)
number prior to 2006, a pointer to the increasing
interest for tannases.
Recombinant Tannases : The tannases of wild
microbial sources do not satisfy all requirements
for optimal versatility in industrial processes. They
exhibit rather limited substrate spectra and are
relatively expensive to purify because they are
secreted only at low levels by their microbial
producers. Obviously, the high-yield production
of fully active recombinant tannases is an
attractive goal, both for basic research and for
industrial purposes. There is therefore an
ongoing search for new sources of tannases and
recombinant technology to produce the same
with more desirable properties for commercial
applications (27). Over-expression of TAN genes
in different hosts seems to be relatively difficult.
Hatamoto et al. (28) cloned and sequenced the
gene-encoding tannase from A. oryzae. Later,
the Aspergillus tannase gene was heterologously
expressed in Saccharomyces cerevisiae,
although with a low yield of protein production.
Conversely, large quantities of enzyme were
obtained when tannase gene was cloned in Pichia
pastoris (29). In addition, A. adeninivorans is
thermo and osmotolerant and can be cultured at
temperatures up to 48 ºC in media containing up
to 20% NaCl. These unusual properties make A.
adeninivorans an ideal host for heterologous
gene expression as well as a useful source of
the same genes for biotechnological significance
(27).
The secreted Arxula tannase was
glycosylated with a carbohydrate content of
31.2%, higher than that of the A. oryzae tannase
(22.7%) but close to the level found in the
recombinant tannase of the A. oryzae produced
in P. pastoris (29). Tannases are often posttranslationally
modified. In A. oryzae, the product
of the tannase gene is translated as a single
polypeptide and then cleaved into two subunits
linked by disulphide bonds (28, 29). In contrast
to the case in A. oryzae, the A. adeninivorans
tannase subunit Atan1p does not undergo post-
Dinesh Prasad et al
146
translational cleavage (except for the removal of
the secretion signal). This may be one of the
reasons why the tannase from Arxula exhibits a
higher specific activity than its counterpart from
A. oryzae (27).
Zhong et al. (29) have described the
successful expression of an A. oryzae TAN gene
in the methylotrophic yeast P. pastoris. For this
purpose the gene was fused to the open reading
frame (ORF) coding for the α-mating-typespecific
genes (MAT-α) sequence and placed
under the control of the methanol-inducible
alcohol peroxidase 1 (AOX1) promoter from P.
pastoris. Recombinant tannase was successfully
secreted by P. pastoris and the productivity of
recombinant tannase was found to be
approximately 3.5-fold higher compared to that
of solid-state fermentation with wild strain (29).
These features will enhance future acceptance
of the transformants as tannase producers in
industrial applications. In another report the
identification and cloning of a gene (tanLpl)
encoding tannase from Lactobacillus plantarum
ATCC 14917 and subsequent expression in P.
pastoris was carried out (30). Curiel et al. (15)
have reported the production and
characterization of recombinant tannase from L.
plantarum. The physicochemical characteristics
exhibited by L. plantarum recombinant tannase
make it an adequate alternative to the currently
used fungal tannases (15).
Substrates for Tannase production : There are
two main categories of tannase substrates
reported i.e. natural and synthetic. Propyl and
methyl gallate are synthetic while tannins are
naturally occurring substrates. Tannins are plant
secondary metabolites and also the second most
abundant group of plant phenolics after lignin (9).
They are defined as naturally occurring watersoluble
polyphenols of varying molecular weight
ranging from 500 to 3000 Da and used as
substrates for tannase production by microbial
fermentation (3, 31).