Cloning, expression and characterization of tannase from Aspergillus species
Albertse, Ewald Hendrik
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Tannin Acyl Hydrolase (E.C. 18.104.22.168) is commonly referred to as tannase. Teighem accidentally discovered this unique enzyme in 1867 (Teighem, 1867). He reported the formation of gallic acid when two fungal species were exposed to an aqueous solution of tannins. The fungal species were later identified as Penicillium glaucum and Aspergillus niger (Lekha & Lonsane, 1997). Tannase is responsible for the hydrolysis of ester and depside linkages in tannins to liberate gallic acid and glucose. This was a very interesting observation due to the usual complexation of proteins with tannic acid and naturally occurring tannins to form water insoluble complexes that inactivates enzymes (Haworth et al., 1985). Tannins have since been shown to be the natural substrate for the tannase enzyme. The enzyme also attacks gallic acid methyl esters, but it possesses high specificity towards the acyl moiety of the substrate. It has been known that certain moulds and fungi belonging to the species Aspergillus and Penicillium produce the enzyme (Rajakumar & Nandy, 1983). According to the work done by Yamada et al., (1968) the enzyme was mainly found intracellularly although the culture broth also contained the enzyme. Aspergillus niger, A. flavus and A. oryzae were found to be the best tannase producers on tannic acid as a sole source of carbon. From these growth studies it became evident that the tannase enzyme was an inducible enzyme (Gupta et al., 1997, Jean et al., 1981 and Mattiason & Kaul, 1994).