The tannin theory of methanogenic toxicity

J. A. Field, S. Kortekaas, G. Lettinga

Research output: Contribution to journalArticlepeer-review

80 Scopus citations


The tannin theory describes the effectiveness of tannic compounds as bacterial inhibitors based on their molecular weight (MW). The inhibition is postulated to result from the hydrogen-bonding of the tannins with bacterial proteins (i.e. enzymes). Oligomeric tannins are expected to be the most effective inhibitors. The oligomeric tannins form stronger hydrogen-bonds with proteins than do their monomers. The high-MW tannins are also reactive with proteins in the bulk solution; however, they are not able to penetrate to bacterial proteins. In this study, tannins were polymerized by autoxidation to colored compounds in order to investigate the role of tannin MW on methanogenic toxicity. The autoxidation of catechin, a tannin monomer, paralleled the expected toxicity as predicted by the tannin theory. The toxicity increased as it was polymerized to oligomeric tannins and decreased as the oligomers were converted to non-toxic high-MW tannins. The autoxidation of green-tea tannins, oligomeric tannins, did not lead to extensive polymerization reactions and no accumulation of high MW tannins was observed. Instead, the toxic green-tea tannins were transformed to colored non-tannic compounds of variable MW, which were non-toxic.

Original languageEnglish (US)
Pages (from-to)241-262
Number of pages22
JournalBiological Wastes
Issue number4
StatePublished - 1989

ASJC Scopus subject areas

  • General Environmental Science
  • Waste Management and Disposal
  • Pollution
  • General Earth and Planetary Sciences


Dive into the research topics of 'The tannin theory of methanogenic toxicity'. Together they form a unique fingerprint.

Cite this