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A thermophilic chain elongating bacterium, strain MDTJ8, was isolated from a thermophilic acidogenic anaerobic digestor producing n-caproate from human waste, growing optimally at 50-55 °C and pH 6.5. 16S rRNA gene analysis suggests that MDTJ8 represents a new species/genus within a group currently composed of mesophilic chain elongators of the Oscillospiraceae family. Genome analysis showed that strain MDTJ8 contains homologues of genes encoding for chain elongation and energy conservation but also indicated n-caproate production from carbohydrates including polymeric substances. This was confirmed by culturing experiments in which MDTJ8 converted, at pH 6.5 and 55 °C, mono-, di- and polymeric carbohydrates (starch and hemicellulose) to n-caproate reaching concentrations up to 283 mg/L and accounting for up to 10 % of the measured fermentation products. MDTJ8 is the first axenic organism that thermophilically performs chain elongation, opening doors to understand and intensify thermophilic bioprocesses targeting anaerobic digestion towards the production of the value-added chemical n-caproate.

The ability of cyanobacterium Arthrospira sp. to assimilate waste nitrogen sources (ammonium and urea) makes it an important candidate for wastewater management. The aim of this work was to evaluate a cultivation approach based on continuous-transitional-feeding regime (nitrate-ammonium-nitrate) in a photobioreactor to assess the effects of ammonium salts on Arthrospira sp. PCC 8005 metabolism. Using a comprehensive biochemical, proteomic and stoichiometric profiling of biomass, this study demonstrated that the proposed cultivation approach could increase the proteins and pigments yields by 20-30%, compared to the respective yields obtained from wild-type Arthrospira sp. strain A light-energy-transfer model was used to predict the biomass and oxygen productivities of Arthrospira sp. cultivated under transitional-feeding regime. 95 ± 2% match was observed between the experimental and simulated productivities. This study thus opened new avenues for use of ammonium rich wastewater for commercial production of high value pigments, biofuel and bioplastics using Arthrospira sp.

The MELiSSA (MicroEcological Life Support System Alternative) project is developing a closed regenerative life support system for long-term space missions by considering the integration of six biological compartments tested in a dedicated pilot plant. The technological effort of building such a closed and sustainable ecological system can also have relevant applications for intensive circular resources reutilization at terrestrial level. In this work, the continuous operation and gas phase connection of two elements of the loop (83 L air-lift Limnospira indica photobioreactor (PBR) and a rat isolator (mock crew)) is performed and modelled. The model includes PBR hydrodynamic characterization, gas-liquid mass transfer and cyanobacteria growth, crew consumption and a control system adjusting light intensity according to oxygen demand. The model is validated in a series of tests where crew compartment oxygen setpoints are sequentially changed to test the global dynamics. The obtained results show a good model performance, as indicated in the low relative error (≤ 0.06) and the high Pearson correlation coefficient and Willmott-d-index obtained for the main variable of the system (0.98–1.00), oxygen concentration, in all cases.

Inspired by a terrestrial ecosystem, Micro-Ecological Life Support System Alternative (MELiSSA) is a project focused on a closed-loop life support system intended for future long-term manned missions (Moon and Mars bases). Started by the ESA in 1989, this 5-compartment concept has evolved through a mechanistic engineering approach designed to acquire both theoretical and technical knowledge. In its current state of development, the project can now start to demonstrate the MELiSSA loop concept at pilot scale. Thus, an integration strategy for a MELiSSA Pilot Plant (MPP) has been defined, describing the different test phases and connections between compartments. The integration steps are due to be started in 2008 and completed with a complete operational loop in 2015. The ultimate objective is to achieve a closed liquid and gas loop fulfiling 100% of oxygen requirements and at least 20% of food requirements for one-man. Although the integration logic could start with the most advanced processes in terms of knowledge and hardware development, this logic needs to be expanded to encompass a high-level simulation policy. This simulation exercise will make it possible to run effective demonstrations of each independent process, followed by progressive coupling with other processes in operational conditions mirroring as far as possible the final configuration. The theoretical approach described in this paper is based on mass balance models of each MELiSSA compartment which are used to simulate each integration step and the complete MPP loop itself. These simulations will help identify criticalities in each integration step and check consistency between objectives, flows, recycling efficiencies and sizing of the pilot reactors. An MPP scenario compatible with current knowledge on the operation of the pilot reactors was investigated, and the theoretical performances of the system were compared against the objectives assigned to the MPP. This scenario makes it possible to highlight the most important integration milestones and simulate their behaviour.

Space exploration programmes, currently under discussion in the US and in Europe, foresee human missions to Mars to happen within the first half of this century. In this context, the European Space Agency (ESA) has conducted a study on the human responses, limits and needs for such exploratory missions, the so-called HUMEX study (ESA SP-1264). Based on a critical assessment of the limiting factors for human health and performance and the definition of the life science and life support requirements performed in the frame of the HUMEX study, the following major critical items have been identified: (i) radiation health risks, mainly occurring during the interplanetary transfer phases and severely augmented in case of an eruption of a solar particle event; (ii) health risks caused by extended periods in microgravity with an unacceptable risk of bone fracture as a consequence of bone demineralisation; (iii) psychological risks as a consequence of long-term isolation and confinement in an environment so far not experienced by humans; (iv) the requirement of bioregenerative life support systems complementary to physico-chemical systems, and of in situ resource utilisation to reach a closure of the life support system to the highest degree possible. Considering these constraints, it has been concluded that substantial research and development activities are required in order to provide the basic information for appropriate integrated risk managements, including efficient countermeasures and tailored life support. Methodological approaches should include research on the ISS, on robotic precursors missions to Mars, in ground-based simulation facilities as well as in analogue natural environments on Earth.

The operation of a fixed bed biofilm reactor for nitrification colonized by Nitrosomonas europaea and Nitrobacter winogradskyi has been characterized in terms of steady state operation but also studying the dynamics of the system in front of disturbances of ammonium load. The nitrifying reactor is used in a biological life support system (BLSS) in which it is necessary to assure high conversion to nitrate and to avoid nitrite production. In order to enhance the knowledge on the system and also as a simulation and control tool, a mathematical model has been developed, calibrated and validated for both steady state and dynamic conditions of continuous mode operation. The results presented demonstrate the applicability of the model to the experimental system, providing a simple and useful mathematical tool to be further applied to the control of the reactor and to maintain the long-term stability of a loop of interconnected bioreactors in the BLSS.

Previous studies have shown that isolated beta-(1,3 and 1,6)-D-glucans and related alkali-extracted fractions from the cell wall of Saccharomyces cerevisiae are able to complex with zearalenone in vitro (affinity up to 50%) and thus may reduce the bioavailability of toxins in the digestive tract. The complexation mechanisms involve cooperative interaction between the two chemical entities that can be computed by Hill's model. Various linear or branched soluble or insoluble beta-D-glucans were evaluated to elucidate their roles in the adsorption mechanisms under three pH conditions (3.0, 6.0, and 8.0) found in the digestive tract. A constant quantity of each beta-D-glucans (1 mg/ml) was mixed at 39 degrees C with increasing amounts of zearalenone (2 to 100 microg/ml), and the amount of bound toxin was measured. Acidic and neutral conditions gave the highest affinity rates (64 to 77%) by beta-(1,3)-D-glucans, whereas alkaline conditions decreased adsorption except when beta-(1,6)-D-glucan side chains were branched on beta-(1,3)-D-glucans. Alkaline conditions appear to impede the active three dimensional conformation of beta-D-glucans and favor single helix and/or random coil structures. Study of the equilibrium between beta-D-glucan-bound and free toxins revealed that two types of chemical interactions occur during toxin complexation with beta-D-glucans, identified as weak chemical linkages such as hydrogen and van der Waals bonds.

Cell walls of yeasts and bacteria are able to complex with mycotoxins and limit their bioavailability in the digestive tract when these yeasts and bacteria are given as feed additives to animals. To identify the component(s) of the yeast cell wall and the chemical interaction(s) involved in complex formation with zearalenone, four strains of Saccharomyces cerevisiae differing in their cell wall glucan and mannan content were tested. Laboratory strains wt292, fks1, and mnn9 were compared with industrial S. cerevisiae strain sc1026. The complex-forming capacity of the yeast cell walls was determined in vitro by modelling the plots of amount of toxin bound versus amount of toxin added using Hill's model. A cooperative relationship between toxin and adsorbent was shown, and a correlation between the amount of beta-D-glucans in cell walls and complex-forming efficacy was revealed (R2 = 0.889). Cell walls of strains wt292 and mnn9, which have higher levels of beta-D-glucans, were able to complex larger amounts of zearalenone, with higher association constants and higher affinity rates than those of the fks1 and sc1026 strains. The high chitin content in strains mnn9 and fks1 increased the alkali insolubility of beta-D-glucans from isolated cell walls and decreased the flexibility of these cell walls, which restricted access of zearalenone to the chemical sites of the beta-D-glucans involved in complex formation. The strains with high chitin content thus had a lower complex-forming capacity than expected based on their beta-D-glucans content. Cooperativity and the three-dimensional structure of beta-D-glucans indicate that weak noncovalent bonds are involved in the complex-forming mechanisms associated with zearalenone. The chemical interactions between beta-D-glucans and zearalenone are therefore more of an adsorption type than a binding type.

The European Space Agency has recently initiated a study of the human responses, limits and needs with regard to the stress environments of interplanetary and planetary missions. Emphasis has been laid on human health and performance care as well as advanced life support developments including bioregenerative life support systems and environmental monitoring. The overall study goals were as follows: (i) to define reference scenarios for a European participation in human exploration and to estimate their influence on the life sciences and life support requirements; (ii) for selected mission scenarios, to critically assess the limiting factors for human health, wellbeing, and performance and to recommend relevant countermeasures; (iii) for selected mission scenarios, to critically assess the potential of advanced life support developments and to propose a European strategy including terrestrial applications; (iv) to critically assess the feasibility of existing facilities and technologies on ground and in space as testbeds in preparation for human exploratory missions and to develop a test plan for ground and space campaigns; (v) to develop a roadmap for a future European strategy towards human exploratory missions, including preparatory activities and terrestrial applications and benefits. This paper covers the part of the HUMEX study dealing with lunar missions. A lunar base at the south pole where long-time sunlight and potential water ice deposits could be assumed was selected as the Moon reference scenario. The impact on human health, performance and well being has been investigated from the view point of the effects of microgravity (during space travel), reduced gravity (on the Moon) and abrupt gravity changes (during launch and landing), of the effects of cosmic radiation including solar particle events, of psychological issues as well as general health care. Countermeasures as well as necessary research using ground-based test beds and/or the International Space Station have been defined. Likewise advanced life support systems with a high degree of autonomy and regenerative capacity and synergy effects were considered where bioregenerative life support systems and biodiagnostic systems become essential. Finally, a European strategy leading to a potential European participation in future human exploratory missions has been recommended.