Tannin degradation

This review of literature on tannin degradation shows that our knowledge of this topic is only very slowly improving. Only a handful of laboratories are currently involved in this area. Of these, the Indian laboratories have made several interesting investigations recently, presumably because they are very active in leather manufacture and need to control the toxicity of their tannery effluents. 

Some microorganisms degrading condensed tannins have been isolated and described, but no reports on the mechanism of the depolymerization process, or the enzymes involved in biodegradation, have appeared. It must be stressed that condensed tannin degradation may be associated with other... 

Tannins may also be broken down by oxidation (Section 6.3.6), although less readily than anthocyanins (Laborde, 1987). The formation of quinones following tannin degradation has been demonstrated and is sometimes accompanied by the opening of the heterocycle. These structural modifications cause the color to evolve towards yellowish-brown hues and precipitation may occur. These reactions are characteristic of wines with very high tannin contents and low anthocyanin concentrations. 

Deschamps A M, Leulliette L 1984 Tannins degradation by yeasts from decaying barks. Int Biodet 20 237-241... 

Osawa R, Kuroiso K, Goto S, Shimizu A (2000) Isolation of tannin-degrading lactobaciUi from humans and fermented foods. Appl Environ Microbiol 66 3093-3097 PaiUard D, Mckain N, Chaudhary LC, Walker ND, Pizette F, Koppova 1, Mcewan NR, Kopeeny J, Vercoe PE, Louis P, Wallace RJ (2007) Relation between phylogenetic position, Upid metabolism and butyrate production by different Butyrivibrio-iike bacteria from the rumen. Anton van Leeuwen 91 417- 22... 

It is not usual for unopened drums of nitrite-based chemical to degrade, and the product should remain in good condition for several years. However, it is possible for tannin-based corrosion inhibitors to degrade, even in unopened drums. Under warm conditions (such as storage in a boil-erhouse) and in the absence of a small amount of suitable microbiocide in the formulation, plastic drums containing tannin products may swell considerably because of microbiological degradation and gas formation. Care is needed to avoid accidents. 

Tannins may be found bound up with magnetite in waterside tube deposits. Degradation products of amines, glycols, polymeric dispersants, chelants, and other organics may also be found and usually are reported in the deposit analysis as a loss on ignition. 

CZE is particularly useful for separating anthocyanin dimers or polymeric anthocyanins. Calvo et al. (2004)" separated 13 anthocyanins by CZE including acylated and non-acylated anthocyanins, pyranoanthocyanins, and flavonol derivatives in wine. Saenz-Lopez et al. (2004)" applied CZE to analyze wine aging (1 to 14 yr) as related to monomeric anthocyanins, anthocyanin derivatives, tannins, and fla-vonols. Bicard et al. (1999)" reported the improved detection sensitivity of anthocyanin chemical degradation analysis by CZE. 

E) coumarins, (F) quinones, (G) flavonoids, (H) tannins, (I) alkaloids, (J) terpenoids and steroids and (K) miscellaneous and unknowns. Although many of these compounds are secondary products of plant metabolism, several are also degradation products which occur in the presence of microbial enzymes. 

It is noteworthy that several of fhe above-mentioned mediators of discoloration have been found fo inhibif sfrepfococcal proliferation. In addition, collagen cross-linking caused by enzymatic and non-enzymat-ic browning or by tannage with tannins might render dentin less susceptible to proteolytic degradation. 

In 1913, Knudson (17) reported that tannic acid (the commercial name of the Chinese gall tannin) could be degraded by a strain of Aspergillus niger previously the French scientist Pottevin (in 1900) had named this enzyme tannase (10). Since then, most of the progress on elucidating the mechanisms of hydrolysable tannin biodegradation has occurred since 1960. 

Degradation of Gallotannins. Different investigations on tannase revealed that this enzyme was not equally efficient on all hydrolyzable tannins. This was particularly true for yeast, whose tannase was effective only on tannic... 

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