Publications by Christof Holliger

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Relatively high concentrations of micropollutants in municipal wastewater treatment plant (WWTP) effluents underscore the necessity to develop additional treatment steps prior to discharge of treated wastewater. Microorganisms that produce unspecific oxida ...

Background: In molecular microbial ecology, massive sequencing is gradually replacing classical fingerprinting techniques such as terminal-restriction fragment length polymorphism (T-RFLP) combined with cloning-sequencing for the characterization of microb ...

Relatively high concentrations of micropollutants such as pharmaceuticals and biocides in municipal wastewater treatment plants (WWTP) effluents underscore the necessity to develop new treatments. Organisms that produce oxidative enzymes such as laccases are a potential means to improve biodegradation of these compounds. Laccases are polyphenol oxidases widespread among plants, fungi and bacteria. They are able to catalyse the oxidation of various aromatic compounds, including several pharmaceuticals and bi

Context Worldwide: FS production much larger than treated volumes In Vietnam: • Urban households required to own septic tanks • Combined onsite and centralized sanitation • FS emptying frequency up to 10 years or more Negligible FS volumes treated before discharge PURR: Partnership for Urban Resource Recovery • Developing knowledge for adequate FS treatment in urban Vietnam • Testing feasibility of anaerobic digestion for FS treatment Study goal To understand the local context and factors influencing the se

Although PCBs production was brought to a halt thirty years ago, recalcitrance to degradation makes them a major environmental pollutant. Previous studies confirmed that organohalide-respiring bacteria (OHRB) were capable of utilizing chlorinated congeners as sole electron acceptor using reductive dehalogenases. OHRB belonging to the Phylum Chloroflexi and Firmicutes are considered as the main degradation drivers. In this study, we aimed at exploring degradation contributions by other taxa using sediment-fr

Simultaneous nitrification-denitrification has been observed in aerobic granular sludge sequencing batch bubble column reactors fed with either acetate or propionate with elimination rates of up to 60-70%. Several in-situ tests under anoxic conditions were performed to evaluate the capacity of the two granular sludges to reduce nitrate (NO3-) and nitrite (NO2-). In absence of dissolved carbon (C), the intracellularly stored carbon acts as electron donor for denitrification. Therefore, the NO3- and NO2- remo

Organohalide respiration (OHR) is a bacterial anaerobic process that uses halogenated compounds, e.g., tetrachloroethene (PCE), as terminal electron acceptors. Our model organisms are Dehalobacter restrictus strain PER-K23, an obligate OHR bacterium (OHRB) ...

Nitrifying wastewater treatment plants (WWTPs) are more efficient than non-nitrifying WWTPs to remove several micropollutants such as pharmaceuticals and pesticides. This may be related to the activity of nitrifying organisms, such as ammonia-oxidizing bac ...

Background Organohalide respiration (OHR) is a bacterial anaerobic process in which chlorinated compound, e.g. tetrachloroethene (PCE), is used as terminal electron acceptors. Dehalobacter restrictus PER-K23, a paradigmatic organohalide-respiring bacterium (OHRB), harbours the pceABCT gene cluster, representing one model system for the study of PCE respiration. To date, the function of PceA, the key enzyme in the process, and PceT, the molecular chaperone for PceA maturation, are well defined. PceB and PceC

During the past 20 years, aerobic granular sludge (AGS) has been extensively studied with the aim to develop an attractive alternative to conventional activated sludge for wastewater treatment. The phosphate-accumulating organism (PAO) Candidatus ‘Accumuli ...

Chlorinated compounds are widespread soil and groundwater pollutants. Because of industrial activities, large amounts of chlorinated ethenes were discharged into the environment over the last decades. The underlying biodegradation process, organohalide respiration (OHR), is a bacterial anaerobic respiration in which the chlorinated compounds, such as chloroethenes, are used as terminal electron acceptors. The key enzyme in OHR is the reductive dehalogenase (RdhA). SL2-PCEb, an enrichment culture dominated b

Aerobic granulation is considered as a promising alternative to conventional activated sludge in biological wastewater treatment. Instead of forming flocs the bacterial communities aggregate to dense granular biofilms. In the present study, granules were cultivated in bubble column reactors operated in sequencing batch mode. The operating cycle consisted of 4 phases: i) an anaerobic feeding phase, ii) a long aeration phase where the sludge was mixed, iii) a short settling phase and finally iv) a withdrawal

Biochemical methane potential (BMP) tests used to determine the ultimate methane yield of organic substrates are not sufficiently standardized to ensure reproducibility among laboratories. In this contribution, a standardized BMP protocol was tested in a l ...

Reductive dehalogenase (rdh) gene clusters encode for proteins involved in organohalide respiration (OHR), a bacterial process where organohalide compounds are used as terminal electron acceptors. RdhK proteins, members of the CRP/FNR family of transcription regulator, are dedicated to the regulation of rdh gene clusters. To date only a few RdhK proteins have been characterized in Desulfitobacterium hafniense while many copies of rdhK genes have been identified within OHR bacteria genomes1,2. RdhK, when bou

Organohalide respiration (OHR) is a bacterial anaerobic energy metabolism that uses many chlorinated organic compounds as terminal electron donors. The process is catalyzed by a class of complex redox enzymes called reductive dehalogenases which harbour a corrinoid and two FeS clusters as cofactors and which are transported across the cytoplasmic membrane via the Twin-arginine translocation (Tat) pathway. The PceT protein is encoded in the conserved pceABCT gene cluster supporting OHR with tetrachloroethene

Background Several enrichment cultures were investigated for their bioremediation potential of tetrachloroethene (PCE). The underlying process (organohalide respiration, OHR) is an anaerobic bacterial respiration during which the chlorinated compounds are used as electron acceptors. The key enzyme in OHR is the reductive dehalogenase (RdhA). SL2-PCEb, an enrichment culture dominated by Sulfurospirillum spp., was shown to stepwise dechlorinate PCE to TCE and cis-DCE, suggesting the successive involvement of

The long-term buffering potential of three silicate minerals (diopside, fayalite and forsterite) present as fine particles in porous quartz sand medium was evaluated in flow-through column experiments over a period of 6.5 months. The columns were operated ...

New-generation bioprocesses using granular sludge aim for a high-rate removal of nutrients from wastewater with low footprint. Achieving enhanced biological phosphorus removal (EBPR) relies on the design of sludge beds and wastewater feeding conditions to ...

Aerobic granular sludge is attractive for high-rate biological wastewater treatment. Biomass wash-out conditions stimulate the formation of aerobic granules. Deteriorated performances in biomass settling and nutrient removal during start-up have however often been reported. The effect of wash-out dynamics was investigated on bacterial selection, biomass settling behavior, and metabolic activities during the formation of early-stage granules from activated sludge of two wastewater treatment plants (WWTP) ove

Accurate control of groundwater pH is of critical importance for in situ biological treatment of chlorinated solvents. The use of ground silicate minerals mixed with groundwater is an appealing buffering strategy as silicate minerals may act as long-term s ...

Christof Holliger

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Bacterial versus fungal laccase: potential for micropollutant degradation

PyroTRF-ID: a novel bioinformatics methodology for the affiliation of terminal-restriction fragments using 16S rRNA gene pyrosequencing data

Laccases: Potential treatment for removal of micropollutants in municipal wastewater?

Selecting appropriate treatment technologies for faecal sludge (FS) from onsite sanitation systems

Indirect evidences for PCB congener degradation by Geobacteraceae in anaerobic sediment-free microcosms

Comparison of the denitrification potential of aerobic granules cultivated with acetate and propionate

Stoichiometry of the Gene Products From the Tetrachloroethene Reductive Dehalogenase Operon pceABCT

Role of ammonia-oxidizing bacteria in micropollutant removal from wastewater with aerobic granular sludge

Organohalide respiration: breakthrough towards the elucidation of the electron-accepting moiety of the respiratory chain

Phage-dependent variability of Candidatus ‘Accumulibacter phosphatis’ populations in aerobic granular sludge

Functional genotyping of Sulfurospirillum spp. in mixed cultures allowed the identification of a new tetrachloroethene reductive dehalogenase

MICROBIAL AND BIOMOLECULAR HETEROGENEITY OF AEROBIC GRANULES WITHIN A SINGLE BIOREACTOR ?

Improving Inter-Laboratory Reproducibility in Measurement of Biochemical Methane Potential (BMP)

Explore RdhK based regulatory network of organohalide respiration using a hybrid proteins strategy

The RdhT protein family: chaperoning bacterial organohalide respiration

Functional genotyping of Sulfurospirillum spp. in mixed cultures allowed the identification of a new tetrachloroethene reductive dehalogenase

Use of silicate minerals for long-term pH control during reductive dechlorination of high tetrachloroethene concentrations in continuous flow-through columns

Modeling Hydraulic Transport and Anaerobic Uptake by PAOs and GAOs During Wastewater Feeding in EBPR Granular Sludge Reactors

Bacterial Selection during the Formation of Early-Stage Aerobic Granules in Wastewater Treatment Systems Operated Under Wash-Out Dynamics

Control of groundwater pH during bioremediation: Improvement and validation of a geochemical model to assess the buffering potential of ground silicate minerals