Screening of Phytophagous and Xylophagous Insects Guts Microbiota Abilities to Degrade Lignocellulose in Bioreactor

Microbial consortia producing specific enzymatic cocktails are present in the gut of phytophagous and xylophagous insects; they are known to be the most efficient ecosystems to degrade lignocellulose. Here, the ability of these consortia to degrade ex vivo lignocellulosic biomass in anaerobic bioreactors was characterized in term of bioprocess performances, enzymatic activities and bacterial community structure. In a preliminary screening, guts of Ergates faber (beetle), Potosia cuprea (chafer), Gromphadorrhina portentosa (cockroach), Locusta migratoria (locust), and Gryllus bimaculatus (cricket) were inoculated in anaerobic batch reactors, in presence of grounded wheat straw at neutral pH. A short duration fermentation of less than 8 days was observed and was related to a drop of pH from 7 to below 4.5, leading to an interruption of gas and metabolites production. Consistently, a maximum of 180 mgeq.COD of metabolites accumulated in the medium, which was related to a low degradation of the lignocellulosic biomass, with a maximum of 5 and 2.2% observed for chafer and locust gut consortia. The initial cell-bound and extracellular enzyme activities, i.e., xylanase and β-endoglucanase, were similar to values observed in the literature. Wheat straw fermentation in bioreactors leads to an increase of cell-bounded enzyme activities, with an increase of 145% for cockroach xylanase activity. Bacterial community structures were insect dependent and mainly composed of Clostridia, Bacteroidia and Gammaproteobacteria. Improvement of lignocellulose biodegradation was operated in successive batch mode at pH 8 using the most interesting consortia, i.e., locust, cockroaches and chafer gut consortia. In these conditions, lignocellulose degradation increased significantly: 8.4, 10.5, and 21.0% of the initial COD were degraded for chafer, cockroaches and locusts, respectively in 15 days. Consistently, xylanase activity tripled for the three consortia, attesting the improvement of the process. Bacteroidia was the major bacterial class represented in the bacterial community for all consortia, followed by Clostridia and Gammaproteobacteria classes. This work demonstrates the possibility to maintain apart of insect gut biological activity ex vivo and shows that lignocellulose biodegradation can be improved by using a biomimetic approach. These results bring new insights for the optimization of lignocellulose degradation in bioreactors

Polyhydroxyalcanoates : une alternative ‘bio’ aux plastiques traditionnels

Ce numéro comprend les articles correspondant aux présentations du Colloque CIAg "Emballages alimentaires : innover pour la sécurité et la durabilité" organisé à Paris le 8 juin 2017.In recent years, the potential of biological routes to replace fossil fuel-based technologies in the drive towards sustainable production of chemicals and energy has been explored and demonstrated. Biodegradable polymers derived from renewable resources could contribute to the global production of plastics (more than 300 million tons per year) currently derived mainly from crude oil refining and, at the same time, reduce the environmental problems caused by plastic disposal by generating a closed carbon cycle. However, cost-effective designs are required if bioprocesses are to be competitive with oil-based equivalents.The polyhydroxyalkanoate (PHA) family consists of a large number of biodegradable polyesters produced by living organisms as carbon and energy reservoir. Short chain length PHAs, or scl-PHAs, are thermoplastics materials whereas medium chain length PHAs, mcl-PHA, are elastomers with good elongation properties that make them suitable for a wide range of applications, forbidden to scl-PHA. While technologies to produce scl-PHA, which most studied representative is PHB, are well known, studies on mcl-PHA are still at an early stage. Mcl–PHAs have been produced in pure culture from low cost materials using Psedudomonas species as biocatalysts. Studies in mixed microbial culture have revealed the possibility of obtaining mcl-PHAs when using a consortium of microorganisms. This strategy does not require costly sterilization operations and makes use of microorganisms’ capability to adapt to different environments and substrates. Enriching mcl-PHA storing bacteria and selecting operational conditions in the production stage that maximize the carbon flow towards mcl-PHA synthesis are essential to obtain processes with large outcomes. In this way, tailored made polyesters containing a stable range of scl and mcl-PHAs, or mcl-PHAs mixed with other natural polymers are environmentally friendly alternatives to conventional plastics and could contribute to the bio-economy developmentAu cours des dernières années, il a été démontré le potentiel des routes biologiques pour remplacer les combustibles fossiles comme ressource pour la production durable de produits chimiques et d'énergie. Ainsi, les polymères biodégradables dérivés de ressources renouvelables pourraient contribuer à la production mondiale de plastiques (plus de 300 millions de tonnes par an) provenant actuellement du pétrole et, en même temps, de réduire les problèmes environnementaux causés par l'élimination des matières plastiques. Cependant, une conception économiquement viable est nécessaire afin de développer des bioprocédés de production de bioplastiques compétitifs avec les équivalents pétroliers.La famille des polyhydroxyalcanoates (PHA) se compose d'un grand nombre de polyesters biodégradables produit par les organismes vivants comme réservoir de carbone et d'énergie. Les PHA à chaîne courte, ou les PHA-scl, sont des matériaux thermoplastiques alors que les PHA à longueur moyenne de chaîne, PHA-mcl, sont des élastomères présentant de bonnes propriétés d'élongation qui les rendent adaptés à une plus large gamme d’applications. Alors que les technologies pour produirePHA-scl, dont le représentant le plus étudié est PHB (polyhydroxybutyrate), sont bien connues, les études sur les PHA-mcl sont plus récentes. Les PHA-mcl ont été produits en culture pure à partir de matériaux à faible coût utilisant des espèces de Pseudomonas comme biocatalyseurs. Des études en culture microbienne mixte ont révélé également la possibilité d'obtenir des PHA-mcl par des consortia microbiens. Cette stratégie ne nécessite pas d'opérations coûteuses de stérilisation et utilise la capacité des microorganismes à s'adapter à différents environnements et substrats. L'enrichissement d’organismes producteurs de PHA-mcl et la sélection des conditions opérationnelles au stade de la production, afin de maximiser le flux de carbone vers la synthèse de la PHA-mcl sont essentiels pour obtenir des procédés efficients. De cette façon, les polyesters fabriqués sur mesure contenant une gamme stable de PHA-scl et PHA-mcl, ou de PHA-mcl mélangés à d'autres polymères naturels, sont des alternatives environnementales aux plastiques d’origine pétrochimique et peuvent contribuer au développent de la bioéconomie

Les micropolluants organiques contenus dans les produits résiduaires organiques ont-ils des impacts écotoxicologiques sur l’écosystème sol ?

National audienc

Removal of the endocrine disrupter nonylphenol and its estrogenic activity in sludge treatment processes

International audienceThe estrogenic compound nonylphenol (NP) is frequently found in sludge from sewage treatment works. Hence, when sewage sludge is spread on the land, endocrine-disrupting compounds may get into the soil. The goal of this study was to investigate the extent to which aerobic mesophilic treatment in continuous reactors permits the removal of NP from sludge and how this process may be useful for treating anaerobically stabilised sludge. We also report on the behaviour of NP during the anaerobic treatment of sludge. The reduction in sludge estrogenic activity observed in the different types of treatment, as measured using estrogen-responsive reporter cells lines (MELN bioassay), was compared with NP removal rates. Under anaerobic conditions, no degradation of NP and its estrogenic activity was observed. Indeed, an accumulation of the compound occurred. In contrast, high removal of NP was achieved in aerobic conditions as well as in aerobic Post-treatment of anaerobically pre-digested sludge, with a concomitant reduction of the sludge's estrogenic potency

Anaerobic lignocellulolytic microbial consortium derived from termite gut: enrichment, lignocellulose degradation and community dynamics

International audienceBackground: Lignocellulose is the most abundant renewable carbon resource that can be used for biofuels and commodity chemicals production. The ability of complex microbial communities present in natural environments that are specialized in biomass deconstruction can be exploited to develop lignocellulose bioconversion processes. Termites are among the most abundant insects on earth and play an important role in lignocellulose decomposition. Although their digestive microbiome is recognized as a potential reservoir of microorganisms producing lignocellulolytic enzymes, the potential to enrich and maintain the lignocellulolytic activity of microbial consortia derived from termite gut useful for lignocellulose biorefinery has not been assessed. Here, we assessed the possibility of enriching a microbial consortium from termite gut and maintaining its lignocellulose degradation ability in controlled anaerobic bioreactors. Results: We enriched a termite gut-derived consortium able to transform lignocellulose into carboxylates under anaerobic conditions. To assess the impact of substrate natural microbiome on the enrichment and the maintenance of termite gut microbiome, the enrichment process was performed using both sterilized and non-sterilized straw. The enrichment process was carried out in bioreactors operating under industrially relevant aseptic conditions. Two termite gut-derived microbial consortia were obtained from Nasutitermes ephratae by sequential batch culture on raw wheat straw as the sole carbon source. Analysis of substrate loss, carboxylate production and microbial diversity showed that regardless of the substrate sterility, the diversity of communities selected by the enrichment process strongly changed compared to that observed in the termite gut. Nevertheless, the community obtained on sterile straw displayed higher lignocellulose degradation capacity; it showed a high xylanase activity and an initial preference for hemicellulose. Conclusions: This study demonstrates that it is possible to enrich and maintain a microbial consortium derived from termite gut microbiome in controlled anaerobic bioreactors, producing useful carboxylates from raw biomass. Our results suggest that the microbial community is shaped both by the substrate and the conditions that prevail during enrichment. However, when aseptic conditions are applied, it is also affected by the biotic pressure exerted by microorganisms naturally present in the substrate and in the surrounding environment. Besides the efficient lignocellulolytic consortium enriched in this study, our results revealed high levels of xylanase activity that can now be further explored for enzyme identification and overexpression for biorefinery purposes

Fate and impact of the antibiotic ciprofloxacin in soils from integrated terrestrial microcosms submitted to pig slurry amendment

National audienc

Enhanced methods for conditioning, storage, and extraction of liquid and solid samples of manure for determination of steroid hormones by solid-phase extraction and gas chromatography-mass spectrometry

Hormones are among the highest-impact endocrine disrupters affecting living organisms in aquatic environments. These molecules have been measured in both wastewater and sewage sludge. Analytical techniques for such matrices are well described in the literature. In contrast, there is little information about the analysis of hormones in animal waste. The objectives of this study were, first, to propose a method for conditioning swine manure samples (addition of formaldehyde, separation of the solid and liquid phases, and duration of storage) in order to determine hormones in the liquid fraction of manure by solid-phase extraction (SPE) coupled with gas chromatography-mass spectrometry (GC-MS). Our results showed that analysis of hormones was affected by matrix changes which occurred during freezing and thawing and after addition of formaldehyde, an additive frequently used to preserve environmental samples. Thus, our results argue for the conditioning of samples without formaldehyde and for separating the solid and liquid fractions of manure before freezing. Second, this study reports on the use of a liquid extraction method coupled with SPE and GC-MS analysis for determination of hormones in the solid fraction of manure. Under the conditions selected, hormone recoveries were between 80 and 100%. Finally, the optimized method was used to quantify hormones in both liquid and solid fractions of swine manure from different breeding units. High levels of estrone and α-estradiol were found in samples whereas β-estradiol was detected in smaller amounts. Estriol and progesterone were mainly found in manure from the gestating sow building whereas testosterone was detected in manure from male breeding buildings

Lignocellulose bioconversion by engineered mixed cultures from cow rumen and termite gut microbiomes

absen

Impact of phosphorus limitation on medium-chain-length polyhydroxyalkanoate production by activated sludge

International audienceFor a sustainable economy, biodegradable biopolymers polyhydroxyalkanoates (PHA) are desirable substitutes to petroleum-based plastics that contaminate our environment. Medium-chain-length (MCL) PHA bioplastics are particularly interesting due to their thermoplastic properties. To hamper the high cost associated to PHA production, the use of bacterial mixed cultures cultivated in open systems and using cheap resources is a promising strategy. Here, we studied the operating conditions favouring direct MCL accumulation by activated sludge, using oleic acid as a model substrate and phosphorus limitation in fed-batch bioreactors. Our results confirm the presence of PHA-accumulating organisms (PHAAO) in activated sludge able to accumulate MCL from oleic acid. A positive correlation between phosphorus (P) limitation and PHA accumulation was demonstrated, allowing up to 26% PHA/total biomass accumulation, and highlighted its negative impact on the MCL/PHA fraction in the polymer. Diversity analysis through 16S rRNA amplicon sequencing revealed a differential selection of PHAAO according to the P-limitation level. A differential behaviour for the orders Pseudomonadales and Burkholderiales at increasing P-limitation levels was revealed, with a higher abundance of the latter at high levels of P-limitation. The PHA accumulation observed in activated sludge open new perspectives for MCL-PHA production system based on P-limitation strategy applied to mixed microbial communities

Earthworms highly increase ciprofloxacin mineralization in soils

Avec les remerciements pour Christelle MarrauldThis report shows that earthworms increase up to eight times the mineralization of the antibiotic ciprofloxacin in soils. Antibiotics are extensively used and disseminated in environmental compartments. Antibiotics may enter food chains and thus induce resistance in environmental and human commensal bacteria. The antibiotic ciprofloxacin is suspected to induce significant adverse effects on soil microbial processes, with possible consequences on soil functions. Nevertheless, little is known concerning the fate of ciprofloxacin in soils. Here, we studied the mineralization and distribution of the [2-14C]-ciprofloxacin in soil–plant–water systems where ciprofloxacin was applied by amendment of spiked pig slurry. Results show that a very weak microbial mineralization of the antibiotic, lower than 0.01 %, occurred after 84 days of incubation. By contrast, the addition of earthworms increased from 5 to 8 times ciprofloxacin mineralization during the following 84 days incubation. In addition, earthworm activity induced the transfer of 40 % of radioactive compounds from the upper to the lower layer of soil, modifying the distribution of the antibiotic within the soil profile. We conclude that earthworms can be used efficiently to mineralize ciprofloxacin and modify its distribution in soils. As a consequence, earthworms change the exposure of soil organisms to ciprofloxacin, and, in turn, the eco-toxicological impact of the antibiotic