Search

To face up abiotic resource depletion and other environmental issues as climate change due to usual fossil-based chemical production technologies, some alternative strategies have been developed using renewable resources. To produce such bio-based chemicals, renewable raw materials such as cereal crops or vegetables are currently used. To promote an environmental responsible practice, organic waste could be a relevant alternative to these dedicated crops. BIORARE technology is an innovative concept based on coupling an anaerobic digestion plant processing with bioelectrosynthesis in order to produce a range of chemicals from organic waste. Even if bioelectrosynthesis processes are not yet technologically mature; it is appropriate to consider the credibility of this emerging technology in environmental terms thanks to an eco-design approach. This eco-design approach is based on the life cycle assessment (LCA) methodology. A LCA of biosuccinic acid production thanks to BIORARE technology has been carried out and has been combined with sensitivity analysis. The aim of this strategy is to ensure that sensitive parameters are identified and adjusted in order to make the technology the more eco-friendly possible whilst maintaining good economy efficiency. The present study describes the identification and optimisation of key parameters of the BIORARE technology applied for succinic acid production. These key parameters and their range of variation are chosen according to a realistic strategy allowing the control of the BIORARE technology on an industrial scale. The results show that the current density applied during the bioelectrosynthesis and the hydrolysis yield during the pre-treatment of the waste stream are key variables in the optimisation between production efficiency and the environmental footprint. The environmental efficiency of the process was studied by applying the eco-efficiency ratio. When the production of biosuccinic acid using the BIORARE technology was compared to a reference scenario, better overall eco-efficiency was shown despite some environmental penalties. In parallel, when the same study was performed for bioethanol production a low efficiency was revealed without environmental penalties. Image 1 • Environmental biorefinery can produce bio-succinic acid from organic wastes. • Eco-design through life cycle assessment helps identifying sensitive parameters. • Trade-offs exist between production efficiency and environmental burdens. [ABSTRACT FROM AUTHOR]

Lignocellulosic materials from municipal solid waste emerge as attractive resources for anaerobic digestion biorefinery. To increase the knowledge required for establishing efficient bioprocesses, dynamics of batch fermentation by the cellulolytic bacterium Ruminiclostridium cellulolyticum were compared using three cellulosic materials, paper handkerchief, cotton discs and Whatman filter paper. Fermentation of paper handkerchief occurred the fastest and resulted in a specific metabolic profile: it resulted in the lowest acetate-to-lactate and acetate-to-ethanol ratios. By shotgun proteomic analyses of paper handkerchief and Whatman paper incubations, 151 proteins with significantly different levels were detected, including 20 of the 65 cellulosomal components, 8 non-cellulosomal CAZymes and 44 distinct extracytoplasmic proteins. Consistent with the specific metabolic profile observed, many enzymes from the central carbon catabolic pathways had higher levels in paper handkerchief incubations. Among the quantified CAZymes and cellulosomal components, 10 endoglucanases mainly from the GH9 families and 7 other cellulosomal subunits had lower levels in paper handkerchief incubations. An in-depth characterization of the materials used showed that the lower levels of endoglucanases in paper handkerchief incubations could hypothetically result from its lower crystallinity index (50%) and degree of polymerization (970). By contrast, the higher hemicellulose rate in paper handkerchief (13.87%) did not result in the enhanced expression of enzyme with xylanase as primary activity, including enzymes from the “xyl-doc” cluster. It suggests the absence, in this material, of molecular structures that specifically lead to xylanase induction. The integrated approach developed in this work shows that subtle differences among cellulosic materials regarding chemical and structural characteristics have significant effects on expressed bacterial functions, in particular the cellulolysis machinery, resulting in different metabolic patterns and degradation dynamics. [ABSTRACT FROM AUTHOR]

In this study isotopic tracing using 13 C labelled pentachlorophenol (PCP) and 2,4,6-trichlorophenol (2,4,6-TCP) is proposed as a tool to distinguish the loss of PCP and 2,4,6-TCP due to biodegradation from other physical processes. This isotopic approach was applied to accurately assess in situ PCP and 2,4,6-TCP degradation under methanogenic conditions in several microcosms made up of household waste. These microcosms were incubated in anaerobic conditions at 35 °C (mesophilic) and 55 °C (thermophilic) without agitation. The volume of biogas produced (CH 4 and CO 2 ), was followed for a period of 130 days. At this stage of stable methanogenesis, 13 C 6 -PCP and 13 C 6 -2,4,6-TCP were introduced anaerobically in microcosms and its monitoring at mesophilic and thermophilic conditions was performed in parallel by gas chromatography mass spectrometry (GC–MS) and gas chromatography isotope-ratio mass spectrometry (GC–IRMS). This study proved the almost total dechlorination of bioavailable PCP and 2,4,6-TCP into 4-CP at 35 °C. Nevertheless, high rate adsorption in particular materials of the two compounds was observed. Furthermore, Carbon-13 Nuclear Magnetic Resonance ( 13 C-NMR) Spectroscopy analysis of 13 C labelled 2,4,6-TCP mesophilic incubations showed the partial mineralization of 4-CP at 35 °C to acetate and then to HCO 3− . Consequently, NMR results confirm the biogas isotopic results indicating the mineralization of 13 C labelled 2,4,6-TCP into 13 C (CH 4 and CO 2 ). Concerning 13 C labelled PCP mesophilic incubations, the isotopic composition of the biogas still natural until the day 262. In contrast, no dechlorination was observed at 55 °C. Thus PCP and 2,4,6-TCP were persistent in thermophilic conditions. [ABSTRACT FROM AUTHOR]

Performance stability is a key issue when managing anaerobic digesters. However it can be affected by external disturbances caused by micropollutants. In this study the influence of phenol on the methanization of cellulose was evaluated through batch toxicity assays. Special attention was given to the dynamics of microbial communities by means of automated ribosomal intergenic spacer analysis. We observed that, as phenol concentrations increased, the different steps of anaerobic cellulose digestion were unevenly and progressively affected, methanogenesis being the most sensitive: specific methanogenic activity was half-inhibited at 1.40 g/L of phenol, whereas hydrolysis of cellulose and its fermentation to VFA were observed at up to 2.00 g/L. Depending on the level of phenol, microbial communities resisted either through physiological or structural adaptation. Thus, performances at 0.50 g/L were maintained in spite of the microbial community's shift. However, the communities' ability to adapt was limited and performances decreased drastically beyond 2.00 g/L of phenol. [ABSTRACT FROM AUTHOR]

In natural settings, anaerobic digestion can take place in a wide temperature range, but industrial digesters are usually operated under either mesophilic (~35 °C) or thermophilic (~55 °C) conditions. The ability of anaerobic digestion microbiota to switch from one operating temperature to the other remains poorly documented. We therefore studied the effect of sudden temperature changes (35 °C/55 °C) in lab-scale bioreactors degrading C-labelled cellulose. An asymmetric behaviour was observed. In terms of methane production, after an adaptation period, mesophilic inoculum exhibited a functional resistance to temperature increase but no functional resilience when temperature was reset to 35 °C, while thermophilic inoculum methanogenic activity strongly decreased under mesophilic conditions but partially recovered when temperature was reset to 55 °C. Automated ribosomal intergenic spacer analysis community fingerprints evidenced a strong influence of temperature on microbial diversity, particularly pronounced and persistent for Archaea. Key phylotypes involved in C-cellulose degradation were identified with a coupled stable isotope probing (SIP)-16S rDNA pyrotag sequencing approach, suggesting that the hydrolytic and fermentative metabolic functions could be maintained thanks to functional redundancy between members of the class Clostridia, whereas methanogenic activity primarily relied on specialized groups affiliated either to genus Methanosarcina (mesophilic conditions), Methanothermobacter or Methanoculleus (thermophilic conditions) that were irreversibly modified by temperature increase. [ABSTRACT FROM AUTHOR]

Cellulose hydrolysis often limits the kinetics and efficiency of anaerobic degradation in industrial digesters. In animal digestive systems, specialized microorganisms enable cellulose biodegradation at significantly higher rates. This study aims to assess the potential of ruminal microbial communities to settle and to express their cellulolytic properties in anaerobic digesters. Cellulose-degrading batch incubations were co-inoculated with municipal solid waste digester sludge and ruminal content. 13C-labeled cellulose degradation was described over time with Gas Chromatography- Combustion- Isotope Ratio Mass Spectrometry. Results were linked to the identification of the microorganisms assimilating 13C and to the monitoring of their relative dynamics. Cellulose degradation in co-inoculated incubations was efficient but not significantly improved. Transient disturbances in degradation pathways occurred, as revealed by propionate accumulation. Automated Ribosomal Intergenic Spacer Analysis dynamics and pyrosequencing revealed that expected classes of Bacteria and Archaea were active and degraded cellulose. However, despite the favorable co-inoculation conditions, molecular tools also revealed that no ruminal species settled in the bioreactors. Other specific parameters were probably needed for this to happen. This study shows that exploiting the rumen's cellulolytic properties in anaerobic digesters is not straightforward. Co-inoculation can only be successful if ruminal microorganisms manage to thrive in the anaerobic digester and outcompete native microorganisms, which requires specific nutritional and environmental parameters, and a meticulous reproduction of the selection pressure encountered in the rumen. [ABSTRACT FROM AUTHOR]

Use of fluorescence excitation-emission spectroscopy as a complementary tool to evaluate the biological stability of municipal solid waste (MSW) during anaerobic degradation was investigated, and whether correlation between the stability of MSW and fluorescence spectroscopic analysis of leachate can be established. In this study, excitation-emission matrix (EEM) spectra indicated the presence of three different fluorophores, centered at Ex/Em wavelength pairs of α: 250-280/315-350 nm; β: 340-350/400-450 nm; and δ: 420-450/470-530 nm; these fluorophores are attributed, respectively, to protein-like, fulvic-like, and humic-like structures. An exhaustive inventory of all fluorescence emission peaks in EEM and in synchronous spectra obtained at different Δλ and different degradation times was compiled. Correlations were sought between emission peaks ( i.e., 280/360, 360/390, 360/470, and 390/430 nm) and standard degradation parameters ( i.e., methane [CH4], CO2, total organic carbon, total inorganic carbon, and pH). Strong correlations were obtained between the cumulative volume of CH4 produced during the biodegradation process and peaks at Ex/Em wavelength pairs 280/360 and 360/390 nm, which were identified as indicators for biological stability. Results of this study encourage the use of fluorescence spectroscopy measurements of leachate as a relatively rapid and valuable tool for the industry and research to assess the degree of MSW stabilization during anaerobic degradation. [ABSTRACT FROM AUTHOR]

This study aimed at providing a better understanding of the influence of support media (10 g/L of zeolites, 10 g/L of activated carbons, and 1 g/L of chitosan) on key phylotypes steering anaerobic digestion (AD) performance in presence of 19 g/L of Total Ammonia Nitrogen (TAN) within batch digesters. Support media did not influence TAN concentration. However, both zeolites and activated carbon 1 reduced methanization lag phase by 47% and 25%, respectively. By contrast, activated carbon 2 and chitosan led to an increase of methanization lag phase by 51% and 32%, respectively. 16S rRNA gene sequencing revealed that zeolites preserved Methanosarcina and enhanced Methanobacterium. In presence of activated carbon 1, Methanoculleus , became predominant earlier than without support while chitosan and activated carbon 2 limited its implantation. This study highlighted potentialities to use supports to enhance AD stability under extreme TAN concentration and evidenced their specific influence on the microbiota composition. [ABSTRACT FROM AUTHOR]

Performance stability is a key operational issue for anaerobic digestion (AD) and phenolic compounds are regularly mentioned as a major cause of digester failures. To get more insights into AD microbiota response to a wide range of inhibition levels, anaerobic batch toxicity assays were conducted with ten phenol concentrations up to 5.00 g/L. Final AD performance was not impaired up to 1.00 g/L. However, progressive shifts in microbial community structure were detected from 0.50 g/L. The methanogenic function was maintained along with increasing initial phenol concentrations up to 2.00 g/L thanks to the emergence of genus Methanoculleus at the expense of Methanosarcina . Within syntrophic populations, family Syntrophomonadaceae proportion was gradually reduced by phenol while Synergistaceae gained in importance in the microbiome. Moreover, at 2.00 g/L, the relative abundance of families belonging to order Clostridiales dropped, leading to the predominance of populations assigned to order Bacteroidales even though it did not prevent final AD performance deterioration. It illustrates the high level of adaptability of archaeal and bacterial communities and suggests the possibility of determining early warning microbial indicators associated with phenol inhibition. [ABSTRACT FROM AUTHOR]

Ammonia inhibition represents a major operational issue for anaerobic digestion (AD). In order to get more insights into AD microbiota resistance, anaerobic batch reactors performances were investigated under a wide range of Total Ammonia Nitrogen (TAN) concentrations up to 50.0 g/L at 35 °C. The half maximal inhibitory concentration (IC 50 ) value was determined to be 19.0 g/L. Microbial community dynamics revealed that above a TAN concentration of 10.0 g/L, remarkable modifications within archaeal and bacterial communities occurred. 16S rRNA gene sequencing analysis showed a gradual methanogenic shift between two OTUs from genus Methanosarcina when TAN concentration increased up to 25.0 g/L. Proportion of potential syntrophic microorganisms such as Methanoculleus and Treponema progressively raised with increasing TAN up to 10.0 and 25.0 g/L respectively, while Syntrophomonas and Ruminococcus groups declined. In 25.0 g/L assays, Caldicoprobacter were dominant. This study highlights the emergence of AD key phylotypes at extreme ammonia concentrations. [ABSTRACT FROM AUTHOR]

Ammonia inhibition represents a major operational issue for anaerobic digestion. In order to refine our understanding of the terminal catabolic steps in thermophilic anaerobic digestion under ammonia stress, we studied batch thermophilic acetate fed experiments at low (0.26 g L −1 ) and high (7.00 g L −1 ) Total Ammonia Nitrogen concentrations (TAN). Although methane production started immediately for all incubations and resulted in methane yields close to stoichiometric expectations, a 62–72% decrease of methanogenic rate was observed throughout the incubation at 7.00 g L −1 of TAN compared to 0.26 g L −1 . Stable Isotope Probing analysis of active microbial communities in 13 C-acetate fed experiments coupled to automated ribosomal intergenic spacer analysis and 16S rDNA pyrotag sequencing confirmed that microbial communities were similar for both TAN conditions. At both TAN levels, the 13 C-labeled bacterial community was mainly affiliated to Clostridia -relatives, with OPB54 bacteria being the most abundant sequence in the heavy DNA 16S rDNA pyrotag library. Sequences closely related to Methanosarcina thermophila were also abundantly retrieved in the heavy DNA fractions, showing that this methanogen was still actively assimilating labeled carbon from acetate at free ammonia nitrogen concentrations up to 916 mg L −1 . Stable isotopic signature analysis of biogas, measured in unlabeled acetate fed experiments that were conducted in parallel, confirmed that acetoclastic methanogenic pathway was dominant at both ammonia concentrations. Our work demonstrates that, besides the syntrophic acetate oxidation pathway, acetoclastic methanogenesis catalyzed by Methanosarcina can also play a major role in methane production at high ammonia levels. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the isotopic tracing using 13C-labeled phenol and bisphenol A was used to study their biodegradation during anaerobic digestion of municipal solid waste. Microcosms were incubated anaerobically at 35°C (mesophilic conditions) and 55°C (thermophilic conditions) without steering. A continuous follow-up of the production of biogas (CH4 and CO2), was carried out during 130d until the establishment of stable methanogenesis. Then 13C12-BPA, and 13C6-phenol were injected in microcosms and the follow-up of their degradation was performed simultaneously by gas chromatography isotope-ratio mass spectrometry (GC–IRMS) and gas chromatography mass spectrometry (GC–MS). Moreover, Carbon-13 Nuclear Magnetic Resonance (13C-NMR) Spectroscopy is used in the identification of metabolites. This study proves that the mineralization of phenol to CO2 and CH4 occurs during anaerobic digestion both in mesophilic and thermophilic conditions with similar kinetics. In mesophilic condition phenol degradation occurs through the benzoic acid pathway. In thermophilic condition it was not possible to identify the complete metabolic pathway as only acetate was identified as metabolite. Our results suggest that mineralization of phenol under thermophilic condition is instantaneous explaining why metabolites are not observed as they do not accumulate. No biodegradation of BPA was observed. [Copyright &y& Elsevier]

Abstract: The goal of this study is to evaluate the impact of the inoculum to substrate ratio (I/S) on the anaerobic degradation potential of municipal solid waste (MSW). Reconstituted MSW samples were thus incubated under batch anaerobic conditions and inoculated with an increasing amount of inoculum originating from a mesophilic sludge digester. I/S tested values were 0 (no inoculum added), 0.015, 0.03, 0.06, 0.12, 0.25, 1, 2 and 4 (gVMinoculum/gVMwaste). The results indicate that the apparent maximal rate of dissolved organic carbon accumulation is reached at I/S=0.12. Under this level, the hydrolysis process is limited by the concentration of biomass and can thus be described as first order kinetics phenomena with respect to biomass for I/S ratios below 0.12. The maximum methane production rate and the minimal latency are reached at a ratio of 2. In addition to that, both methane signature and ARISA show a shift in the methanogenic populations from hydrogenotrophic to acetoclastic. [Copyright &y& Elsevier]

• Microbial electrosynthesis in a microbial electrolysis cell is first demonstrated. • A dedicated control strategy allows stable operation at 5 A/m2 for months. • Up to 4 times less power consumed compared to electrosynthesis with abiotic anode. • Powering microbial electrolysis with anaerobic digestion (AD-MEC) is evaluated. • Up to 22% of COD from waste may be converted to organic products in AD-MEC. Environmental biorefineries aim to produce biofuels and platform biomolecules from organic waste. To this end, microbial electrochemical technologies theoretically allow controlled microbial electrosynthesis (MES) of organic molecules to be coupled to oxidation of waste. Here, we provide a first proof of concept and a robust operation strategy for MES in a microbial electrolysis cell (MEC) fed with biowaste hydrolysates. This strategy allowed stable operation at 5 A/m2 for more than three months in a labscale reactor. We report a two to four-fold reduction in power consumption compared to microbial electrosynthesis with water oxidation at the anode. The bioelectrochemical characterizations of the cells were used to compute energy and matter balances for biorefinery scenarios in which anaerobic digestion (AD) provides the electricity and CO 2 required for the MEC. Calculations shows that up to 22% of electrons (or COD) from waste may be converted to organic products in the AD-MEC process. [ABSTRACT FROM AUTHOR]