<b>Molecular and biochemical</b><b> characterization of extracellular tannin acyl hydrolase activity from a Mexican isolate of <i style="">Aspergillus niger</i></b>

Abstract

Microbial tannase, a hydrolysable tannin-degrading enzyme, is extensively used in manufacture of instant tea, beer, wine, and gallic acid. <i style="">Aspergillus niger</i> strain, obtained from a Mexican tannery wastewaters rich in gallic acid [Quebracho Phenolics-rich Tannery Wastewaters, (QPTW)], displayed a good growth and tannase activity in a minimal medium added with 1% (w/v) QPTW (Kr= 0.451 mm.h^-1). Using PCR and RACE 3´ and 5´methodologies, a complete cDNA of a tannase was cloned from this isolate.Nucleotide sequence of complete cDNA was of 4690 bp with a complete ORF of 1833 bp encoding 611 amino acids. Transcriptionalinduction was observed in mineral medium added with carbon sources as tannic acid alone (1 and 10 g/l), as well as mix of glucose(1 and 10 g/l) and tannic acid (1 g/l) in the media. However, neither glucose (1 and 10 g/l) and sucrose (1 and 10 g/l) nor (+)-catechin(1 and 10 g/l) as sole carbon sources displayed gene induction in <i>in vitro</i> assays. <i style="">A. niger</i>-GTO is a new strain with interesting characteristics for industrial tannase production purposes.