Wattle tannin, source

Condensed tannins were considered to be highly recalcitrant to biodegradation until Basaraba (3) reported that some bacterial isolates could utilize wattle tannin as both a carbon and energy source. Later, Lewis and Starkey... 

Most of the recent efforts to develop uses for the condensed tannins have centered on their application in wood adhesives. Reviews by Pizzi (182, 186) and others (15, 78, 87, 93, 208) provide references to several hundred papers and patents on this subject. Despite world-wide research efforts on other sources of tannins, particularly since the 1972-1973 petroleum shortage, the mimosa or wattle tannins extracted from the bark of black wattle Acacia mearnsii) remain the major source of condensed tannins exploited commercially for adhesive manufacture. Of the approximately 100000 tons of wattle tannin produced annually, only about 10000 tons are used in wood adhesives, predominantly in South Africa but also in Australia and New Zealand (186). The extensive use of wattle tannins by the wood products industry of South Africa is impressive indeed, as these tannins have partly replaced phenol and resorcinol usage in adhesives for bonding of particleboard, plywood, and laminated timbers (182, 186, 213). Three factors have contributed to the success in use of wattle tannin-based adhesives, namely the comparatively high costs of phenol and resorcinol in the Southern Hemisphere, their resorcinolic functionality and low molecular weight and, perhaps most importantly, the commitment by the research and industrial communities of these countries to reduce the reliance of the forest products industry on petroleum-based adhesives. 

The tannins are synthesized by plants and are abundantly distributed in many different forms of plant life. Common sources of tannins include for example, the bark, leaves, fruit and roots of many plants most tannins, however, have been and are still derived from the bark of a few trees and shrubs, such as oak, chestnut, hemlock, mangrove, quebracho, and wattle, from which they are generally extracted with water. 

Yeasts. An interesting paper published in 1984 (59) claimed that rat-caecal microflora degraded catechin. To our knowledge no paper has dealt with yeasts, other than that some yeasts degrading wattle of quebracho tannins were able to grow weakly with catechin as a sole carbon source (32). 

The Type 1 proanthocyanidins are distributed almost ubiquitously in the woody plants, whereas Type 2 proanthocyanidins are confined to certain families in the Leguminosae and Anacardiaceae (see Sect. 7.7.3.1), often co-existing with Type 1 proanthocyanidins either in the same or different organs of the plant. However, the Type 2 tannins are of pre-eminent importance commercially as currently the two most important sources of condensed tannins for industrial applications are wattle Acacia mearnsii) bark and quebracho Schinopsis spp.) wood, which are both of this type (Chap. 10.3). Our current knowledge of these tannins is almost entirely due to the efforts of David Roux and his colleagues over the past three decades. 

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