Tannin microbial degradation

Microbial Degradation of Catechin. Since (+) catechin is a possible biodegradation product from condensed tannins, its utilization and bioconversion have been extensively examined by several research groups using fungi, bacteria and yeasts. 

The gallic acid used in the preparation of 1,2,3-benzenetriol can be obtained by microbial degradation of tannins, which are complex combinations of glucose and gallic acid obtained from oak bark and gallnuts. A few other representatives of the many types of naturally occurring derivatives of polyhydric arenols are... 

There are also structural differences between humic substances or UDOM collected from rivers and oceans (Table I). Humic substances and UDOM from rivers are enriched in aromatic components compared with their counterparts from the ocean. Terrestrial vegetation is relatively rich in aromatic components, such as lignins and tannins, and this is reflected in the greater aromatic nature of DOM in rivers. These biopolymers are relatively resistant to microbial degradation and are important components of river DOM. Humic substances and UDOM from the ocean are enriched in carbohydrates compared with their counterparts from rivers. This is consistent with observations of higher C-normalized yields of neutral sugars in bulk DOM from the ocean compared with rivers (Table I). 

Grant W D 1976 Microbial degradation of condensed tannins. Science 193 1137—1139... 

Bhat TK, Makkar HPS, Singh B (1996) Isolation of a tarmin-protein complex-degrading fungus from faeces of hiU cattle. J Appl Microbiol 22 257-258 Bhat TK, Singh B, Sharma OP (1998) Microbial degradation of tannins - a cruient perspective. Biodegradation 9 343-357... 

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. 

As plant tissues senesce and die, three processes may ensue almost simultaneously. First, enzymes within the dead but sterile and physically intact cells cause proteolysis and other autolytic degradations. The released amino acids, sugars, tannins, phenols, and quinones may be oxidized by chemical or enzymatic catalysis to produce humus-like pigments, or proto-humus as discussed by Stevenson in Chapter 2. This was well illustrated by Cohen (Given and Dickinson, 1975) who observed cellular material of partially polymerized eaco-anthocyanins in residues of Rhizophora mangle deposited in a mangrove swamp in Florida. The autolytic reactions may be prominent in situations where microbial decomposition is slow due to acidity, anaerobiosis, or lack of basic nutrients. 

In turn, secondary metabolites serve as sources of carbon for decomposer organisms. Thus, microorganisms can play an important role in the detoxification of litter by the degradation of these secondary metabolites. Tannins of low molecular weight can act as carbon substrates for microorganisms when they are adapted to this type of compound. In fact, microbial communities which have had a limited exposure to taimins during their development seem to be more sensitive to these compounds. 

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