Effect of humic acids on the activity of pure and mixed methanogenic cultures

Ahmad F. Khadem*, Samet Azman, Caroline M. Plugge, Grietje Zeeman, Jules B. van Lier, Alfons J M Stams

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

25 Citations (Scopus)


The impact of humic acid (HA) on methanogenic activity was investigated. Methanogenic crushed granular sludge and pure cultures of mesophilic methanogens were incubated in batch cultures with HA. Initial methane production rates and substrate consumption rates were quantified. In the presence of 1 kg m−3 HA, the methane production rate of all hydrogenotrophic methanogens was inhibited by more than 75%, except Methanospirillum hungatei that was not inhibited up to 5 kg m−3 HA. The acetoclastic Methanosarcina barkeri was completely inhibited by HA ≥1 kg m−3. However, Methanosaeta concilii was only slightly affected by HA up to 3 kg m−3. When methanogenic granular sludge was incubated with HA, the specific methanogenic activity (SMA) tests showed less inhibition, when compared to the pure cultures of methanogens. The SMA test with H2/CO2, formate and acetate showed reduced initial methane production rate of 42%, 23% and 40%, respectively. Differences in HA susceptibility were explained by differences in cell wall structure.

Original languageEnglish
Pages (from-to)21-30
Number of pages10
JournalBiomass & Bioenergy
Publication statusPublished - 1 Apr 2017


  • Activity tests
  • Anaerobic sludge
  • Humic acid
  • Inhibition
  • Methanogenesis


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