Towards a standardization of biomethane potential tests

8 PáginasProduction of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. A workshop was held in June 2015 in Leysin Switzerland to agree on common solutions to the conundrum of inconsistent BMP test results. A discussion covers actions and criteria that are considered compulsory ito accept and validate a BMP test result; and recommendations concerning the inoculum substrate test setup and data analysis and reporting ito obtain test results that can be validated and reproduced.The workshop in Leysin, Switzerland, has been financed by the Swiss Federal Office for Energy, and co-sponsored by Bioprocess Control Sweden AB, Lund, Sweden. The authors thank Alexandra Maria Murray for editing the English

Hemolymph microbiome of Pacific oysters in response to temperature, temperature stress and infection

Microbiota provide their hosts with a range of beneficial services, including defense from external pathogens. However, host-associated microbial communities themselves can act as a source of opportunistic pathogens depending on the environment. Marine poikilotherms and their microbiota are strongly influenced by temperature, but experimental studies exploring how temperature affects the interactions between both parties are rare. To assess the effects of temperature, temperature stress and infection on diversity, composition and dynamics of the hemolymph microbiota of Pacific oysters (Crassostrea gigas), we conducted an experiment in a fully-crossed, three-factorial design, in which the temperature acclimated oysters (8 or 22 °C) were exposed to temperature stress and to experimental challenge with a virulent Vibrio sp. Strain. We monitored oyster survival and repeatedly collected hemolymph of dead and alive animals to determine the microbiome composition by 16s rRNA gene amplicon pyrosequencing. We found that the microbial dynamics and composition of communities in healthy animals (including infection survivors) were significantly affected by temperature and temperature stress, but not by infection. The response was mediated by changes in the incidence and abundance of operational taxonomic units (OTUs) and accompanied by little change at higher taxonomic levels, indicating dynamic stability of the hemolymph microbiome. Dead and moribund oysters, on the contrary, displayed signs of community structure disruption, characterized by very low diversity and proliferation of few OTUs. We can therefore link short-term responses of host-associated microbial communities to abiotic and biotic factors and assess the potential feedback between microbiota dynamics and host survival during disease

Towards a standardization of biomethane potential tests

Production of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. Although several norms and guidelines for BMP tests exist, inter-laboratory tests regularly show high variability of BMPs for the same substrate. A workshop was held in June 2015, in Leysin, Switzerland, with over 40 attendees from 30 laboratories around the world, to agree on common solutions to the conundrum of inconsistent BMP test results. This paper presents the consensus of the intense roundtable discussions and cross-comparison of methodologies used in respective laboratories. Compulsory elements for the validation of BMP results were defined. They include the minimal number of replicates, the request to carry out blank and positive control assays, a criterion for the test duration, details on BMP calculation, and last but not least criteria for rejection of the BMP tests. Finally, recommendations on items that strongly influence the outcome of BMP tests such as inoculum characteristics, substrate preparation, test setup, and data analysis are presented to increase the probability of obtaining validated and reproducible results.info:eu-repo/semantics/publishedVersio

Manipulation of dietary conditions for maximal growth in mussels Mytilus edulis from the Marennes-Oleron Bay France

Results are presented from laboratory-based experiments in which we investigated short-term responses of Mytilus edulis L. to experimental changes in the amount and composition of suspended seston. Working with large quantities of cultured algae, we have studied feeding behaviour over ranges of food availability and quality that ex tend weil beyond earlier limits. Findings confirm the ability of mussels to selectively reject inorganic particles as pseudofaeces prior to ingestion, thereby enriching the organic content of ingested matter by 30% more than the organic content of natural filtered seston. Our findings also establish acclimation both of selective and absorptive processes, indicating that the extent to which growth of M. edulis can be stimulated in the short-term will depend upon prior nutritional history. Present maximal growth of 14.8% dry soft tissue d-I in a standard M. edulis of 1 g dry soft tissue was much higher than has previously been documented for any adult musse!. Maximal growth was achieved when natural ses ton that had been enriched to more than about 60% organic content with a mixture of algal monocultures was available al concentrations above about 11.5 mg total particulates 1-1 • Neither ingestion rate nor net energy balance were improved with further increases in food availability, associated with regulatory reductions in the rate of water filtration (clearance rate) that maintained organic ingestion rate independent of increases in bath the amount and organic content of available seston. These findings suggest that digestive processes had become saturated when organic ingestion reached about 6.5 mg organics g-I dry soft tissue h-I in a standard M. edulis of 1 g dry soft tissue, representing as much as 20.6% of all soft tissue organic mass mussel-1 d-1. Such saturation of organic ingestion is consistent with previous conclusions based on comparative allometries showing that limitations to growth in M. edulis and other bivalves are associated with the rate of food processing.Des expérimentations ont été réalisées en laboratoire pour déterminer les réponses à court terme de la moule Mytilus edulis soumise à des changements dans la quantité et la qualité de la nourriture. L'apport de fortes quantités d'algues phytoplanctoniques a permis d'étudier le comportement de la moule pour des conditions supérieures à celles décrites antérieurement. Les résultats confirment que la moule rejette préférentiellement les particules minérales dans les pseudofèces, induisant un enrichissement de 30 % de la matière organique ingérée par rapport à la matière organique filtrée. Ainsi, l'acclimatation aux conditions nutritionnelles agit sur les phénomènes de sélection et d'absorption. La croissance de Mytilus edulis peut être stimulée à court terme en fonction de son passé nutritionnel. La croissance maximale obtenue, pour une charge sestonique de 11,5 mg.l- 1 composée de 60 % de matière organique, est de 14,8 % de chair sèche; calculée pour un animal standard de 1 g de chair sèche et par jour, cette croissance est nettement supérieure à celle décrite précédemment pour des moules adultes. Une augmentation de la concentration de la nourriture disponible n'engendre pas d'amélioration, ni de la quantité de matière organique ingérée, ni du bilan énergétique. En effet, ces fonctions physiologiques sont associées à des réductions compensatoires de la filtration de l'animal qui maintiennent l'ingestion de la matière organique indépendante d'une part, de la charge et d'autre part, du taux de matière organique du seston disponible. En conséquence, les processus digestifs atteindraient un seuil de saturation lorsque l'ingestion organique correspondrait à 6,5 mg de matière organique par heure, pour une moule standard de 1 g de chair sèche; ce qui représente près de 20,6 % du poids de matière organique de la chair, par moule et par jour. Une telle saturation de l'ingestion organique est cohérente avec les conclusions antérieures basées sur des aIlométries comparatives, qui montrent que les limites de croissance chez M. edulis et d'autres bivalves sont associées aux taux d'utilisation de la nourriture