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Visual reading method for detection of bacterial tannase

Osawa, R & Walsh, TP 1993, Applied and Environmental Microbiology, vol. 59, no. 4, pp. 1251-1252.

The authors of this study develop and describe a new visual reading method for detecting the presence of tannase in cultures of bacteria that can degrade the tannin-protein complexes present in eucalypts, the main food source for the koala.

  A tannase is an enzyme that catalyses the hydrolysis, or chemical bond-breaking, of gallic acid esters. Gallic acid is found in tannins, which are biomolecules that bind to proteins to form chemical complexes called ‘tannin-protein complexes’, and these occur in high concentrations in eucalypts. Koalas, therefore, require a mechanism to ‘degrade’ these complexes to extract the protein for metabolism. In this study, three different methods were trialled for detecting bacterial tannase activity in six different bacterial strains, including two strains of tannin-protein complex degrading enterobacteria and three strains of tannin-protein complex degrading S. bovis which is known to occur in koala faeces. The three methods were reversed-phase high-performance liquid chromatography, spectrophotometry, and visual reading. In the visual reading method, the observation of two phenomena confirmed the presence of tannase in the sample cultures: firstly the green to brown colouration of the gallic acid, and secondly the hydrolysis of methyl gallate to release free gallic acid.

  As well as its effectiveness for detecting bacterial tannase activity, the visual reading method is recommended for its simplicity and cost-efficiency compared to other methods trialled, which required more sophisticated equipment. The development of a simple and reliable method for the detection of bacterial tannase such as that described in this study is significant for improving understandings of the mechanisms by which koalas can sustain a high-tannin diet.

 

Summarised by Joanna Horsfall

 

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