Genome sequence of Nitratireductor aquibiodomus strain RA22

Influence of operational conditions on the performance of biogas bioconversion into ectoines in pilot bubble column bioreactors

The application of biogas as a low-priced substrate for the production of ectoines constitutes an opportunity to decrease their production costs and to enhance the viability of anaerobic digestion. The influence of operational conditions on CH₄-biogas biodegradation and on ectoines production yields was assessed in continuous pilot bubble column bioreactors. The rise in biomass concentration from 1 to 3 g L^-1 resulted in a decrease in the specific ectoine content from 42 ± 8 to 30 ± 4 mg_ectoine g_VSS^-1. The concentration of Cu²⁺ and Mg²⁺ did not impact process performance, while the use of ammonium as N source resulted in low CH₄ biodegradation and ectoine yields (13 ± 7 mg_ectoine g_VSS^-1). The increase in CH₄ content from 4.5 to 9 %v·v^-1 enhanced CH₄ removal efficiency. Process operation at NaCl concentrations of 3 %w·w^-1 instead of 6 %w·w^-1 decreased the ectoine yield to 17 mg_ectoine g_VSS^-1. Finally, Methylomicrobiumburyatense was identified as the dominant species.

A systematic comparison of ectoine production from upgraded biogas using Methylomicrobium alcaliphilum and a mixed haloalkaliphilic consortium

Biogas is the byproduct of anaerobic digestion with the highest valorization potential, however its full exploitation is limited by the lack of tax incentives and the inherent presence of pollutants. The development of technologies for biogas conversion into added-value products is crucial in order to ensure the competitiveness of this bioresource. This study constitutes the first proof of concept of upgraded biogas bioconversion into the high profit margin product ectoine. Ectoine represents the most expensive product synthesized by microorganisms with a retail value of 1000 $ kg^-1 and a yearly increasing demand that currently entails a total market opportunity of 15000 M€. First, the production of ectoine from upgraded biogas was assessed in batch bioreactors. The presence of H₂S did not exert a negative effect on the growth of the haloalkaliphilic ectoine producers, and ectoine yields up to 49 mg g biomass^-1 were obtained. A second experiment conducted in continuous bubble column bioreactors confirmed the feasibility of the process under continuous mode (with ectoine yields of 109 mg g biomass^-1). Finally, this study revealed that the removal of toxic compounds (i.e. medium dilution rate of 0.5 day^-1) and process operation with a consortium composed of methylotrophic/non-methylotrophic ectoine producers enhanced upgraded biogas bioconversion. This research discloses the basis for the application of this innovative technology and could boost the economic performance of anaerobic digestion.

Acclimation of a marine microbial consortium for efficient Mn(II) oxidation and manganese containing particle production

Sediment contamination with metals is a widespread concern in the marine environment. Manganese oxidizing bacteria (MOB) are extensively distributed in various environments, but a marine microbial community containing MOB is rarely reported. In this study, a consortium of marine metal-contaminated sediments was acclimated using Mn(II). The shift in community structure was determined through high-throughput sequencing. In addition, the consortium resisted several harsh conditions, such as toxic metals (1mM Cu(II) and Fe(III)), and exhibited high Mn(II) oxidation capacities even the Mn(II) concentration was up to 5mM. Meanwhile, biogenic Mn containing particles were characterized by scanning electron microscope (SEM), X-ray powder diffraction (XRD), and N2 adsorption/desorption. Dye removal performance of the Mn containing particles was assayed using methylene blue, and 20.8 mg g(-1) adsorption capacity was obtained. Overall, this study revealed several new genera associated with Mn(II) oxidation and rare biogenic Na3MnPO4CO3. Results suggested the complexity of natural microbe-mediated Mn transformation.