Growing concentrations of phenol increasingly modify microbial communities' dynamics and performances' stability of anaerobic digesters

O. Chapleur (1) , Raphaël Civade (1) , Carolina Hoyos-Hernandez (1) , Laurent Mazéas (1) , T. Bouchez (1)

1 UR HBAN - Hydrosystèmes et Bioprocédés

Anaerobic degradation requires a complex network of interacting and competing microorganisms. Waste anaerobic digesters are based on the intensive use of this flora. Consequently, functioning and stability of digesters are directly related to microbial populations' dynamics. The latter may be subject to external disturbances, such as the arrival of micropollutants with waste, causing malfunction of bioprocesses. In this context, we questioned the influence of phenol addition on microbial communities degrading cellulose under anaerobic conditions. For that purpose, cellulose batch digesters were set-up and inoculated with municipal solid waste digester sludge. Modifications of microbial dynamics and degradation performances after addition of phenol were evaluated in triplicates (nine different concentrations tested, from 0 to 4g.L-1). Gas production, reaction pathways and phenol concentration were followed over time. These results were linked to the monitoring of microorganisms' dynamics (automated-ribosomal-intergenic-spacer-analysis method, ARISA and qPCR on functional gene and on total Archaea and Bacteria) and of their spatial organisation (fluorescent-in-situ-hybridization, FISH). With increasing phenol concentrations, increasing disruption of digesters' performances (gas production, intermediates accumulation) was observed. EC50 (half-maximal effective-concentration) values for phenol was calculated from the dose/effect curve obtained by plotting degradation parameters as a function of phenol concentration. With increasing concentration, intermediates pathways were modified; Archaea activity was totally inhibited from 1.5g.L-1, Bacteria activity from 2.0g.L-1. Moreover, phenol degradation was observed in several digesters after several weeks. ARISA monitoring revealed an important influence of phenol concentration on microbial dynamics in general. qPCR gave more specific information. Physico-chemical and microbial results were linked to establish patterns of communities' perturbation by phenol. A phenol inhibition threshold was established for several microorganisms. Subdominant microorganisms that used phenol perturbation to settle and phenol degrading microorganisms were identified. This study gives important insights in the understanding of micropollutants effect on complex microbial communities' dynamics and their influence on digesters' stability.

Mots clés: DIGESTEUR ANAEROBIE; CELLULOSE; MICROPOLLUANT ORGANIQUE; PHENOL

Domaines: Sciences de l'environnement

O. Chapleur, Raphaël Civade, Carolina Hoyos-Hernandez, Laurent Mazéas, T. Bouchez. Growing concentrations of phenol increasingly modify microbial communities' dynamics and performances' stability of anaerobic digesters. 13th World Congress on Anaerobic Digestion : Recovering (bio) Ressources for the World, Jun 2013, Santiago de Compostella, Spain. ⟨hal-01118701⟩