d(GC) - Association of Biotechnology and Pharmacy
d(GC) - Association of Biotechnology and Pharmacy
d(GC) - Association of Biotechnology and Pharmacy
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Current Trends in <strong>Biotechnology</strong> <strong>and</strong> <strong>Pharmacy</strong><br />
Vol. 6 (2) 145-165 April 2012, ISSN 0973-8916 (Print), 2230-7303 (Online)<br />
Tannins are widely distributed in different<br />
parts (barks, needles, heartwood, grasses, seeds<br />
<strong>and</strong> flowers) <strong>of</strong> vascular plants (32) <strong>and</strong> they are<br />
further classified into two major groups:<br />
hydrolysable <strong>and</strong> condensed tannins (33). The<br />
hydrolysable tannins (Fig. 1) are constituted by<br />
several molecules <strong>of</strong> organic acids such as gallic,<br />
ellagic, digallic <strong>and</strong> chebulic acids, esterified to<br />
a core molecule <strong>of</strong> glucose. Also molecules with<br />
a core <strong>of</strong> quinic acid instead <strong>of</strong> glucose also<br />
considered as hydrolysable tannins. Condensed<br />
tannins or proanthocyanidins are complex<br />
compounds constituted by flavonoid groups (2<br />
to 50) which are considered not to be<br />
hydrolysable (Fig. 2). Their major constituents<br />
are cyanidin <strong>and</strong> delphinidin which are also<br />
responsible for the astringent taste <strong>of</strong> fruit <strong>and</strong><br />
wines (26, 34).<br />
The selection <strong>of</strong> a substrate for tannase<br />
production by fermentation depends on several<br />
Fig. 1. Structure <strong>of</strong> hydrolysable tannins [Gallotannin<br />
(A), Ellagitannins (B), Ellagic acid (C),<br />
Hexahydroxyphenic acid (D).<br />
147<br />
Fig. 2. Structure <strong>of</strong> a typical condensed tannins.<br />
Condensed tannins are all oligomeric <strong>and</strong> polymeric<br />
proanthocyanidins. ‘n’ denotes number <strong>of</strong> flavonoid<br />
groups (2 to 50).<br />
factors viz., cost, availability <strong>and</strong> suitability <strong>of</strong> the<br />
substrate for obtaining the desired yield <strong>of</strong><br />
tannase, <strong>and</strong> thus requires screening <strong>of</strong> several<br />
agro-industrial <strong>and</strong> forest residues (35, 36)<br />
Mukherjee <strong>and</strong> Banerjee (35) evaluated the<br />
various substrates for production <strong>of</strong> tannase <strong>and</strong><br />
gallic acid on the basis <strong>of</strong> their tannin contents<br />
as 30-41% in case <strong>of</strong> myrobalan fruit (Terminalia<br />
chebula), 10-14.1% for tea leaf <strong>and</strong> 40-52% in<br />
case <strong>of</strong> teri pod (Caesalpinia digyna) cover<br />
powder (37). Optimum tannase activity <strong>and</strong> yield<br />
were reported with a mixed substrate <strong>of</strong><br />
myrobalan <strong>and</strong> teri pod powder at a fixed ratio<br />
(4:6) with maximum gallic acid production.<br />
Microbial degradation <strong>of</strong> condensed tannins<br />
is less documented than that <strong>of</strong> gallotannins;<br />
however, it is known that the selective hydrolysis<br />
<strong>of</strong> galloyl groups <strong>of</strong> the ellagitannins is catalyzed<br />
by tannase (4). Ellagic acid production from<br />
cranberry pomace (Vaccinium microcarpum) by<br />
SSF using a fungus Lentinus edodes has been<br />
reported, attributing the catalysis to the enzyme<br />
β-glucosidase (38). A review work <strong>of</strong> Li et al.<br />
(3), presents information on tannase production<br />
by species <strong>of</strong> Lactobacillus, Leuconostoc,<br />
Oenococcus, <strong>and</strong> Pediococcus, using substrate<br />
Overview on production <strong>and</strong> characterization <strong>of</strong> tannases