Biohydrogen production by Thermotoga maritima from a simplified medium exclusively composed of onion and natural seawater

International audienc

Effect of salinity and temperature on the bacterial diversity shift of anaerobic batch cultures treating abattoir wastewater

International audienceThe molecular biological analyses allowed to highlight the changes of the microflora of the batch cultures with the increase of the salinity and the temperatures. The single-strand conformation polymorphism (SSCP) patterns of the bacterial diversity at different salt concentrations (0, 20, and 40gl(-1)) in mesophilic (37 degrees C) and thermophilic (55 degrees C) conditions showed that the bacterial diversity varies depending on the culture conditions. The obtained SSCP profiles at the different salt concentrations showed that there is a greater diversity in the mesophilic than the thermophilic condition. However, the bacterial diversity richness (1/D) and the species evenness for the mesophilic condition for all the tested salt concentrations showed firstly the maximum diversity and secondly that the species in the sample are quite evenly distributed. The increase of the salt concentration to 20 and 40gl(-1) at thermophilic condition decreased the bacterial diversity due to the selection pressure caused by the elevation of salinity, which eliminated the salt-sensitive species and thus reduced the community diversity

Characterization of Defluviitalea saccharophila gen. nov., sp. nov., a thermophilic bacterium isolated from an upflow anaerobic filter treating abattoir wastewaters, and proposal of Defluviitaleaceae fam. nov.

A novel thermophilic, anaerobic, Gram-stain-positive, terminal-spore-forming bacterium was isolated from an upflow anaerobic filter treating abattoir wastewaters in Tunisia. This strain, designated LIND6LT2(T), grew at 40-60 °C (optimum 50-55 °C) and at pH 6.0-8.5 (optimum pH 7.0-7.5). It did not require NaCl for growth, but tolerated it up to 2%. Sulfate, thiosulfate, elemental sulfur, sulfite, nitrate and nitrite were not used as electron acceptors. Growth of LIND6LT2(T) was inhibited by sulfite (2 mM). Strain LIND6LT2(T) used cellobiose, glucose, mannose, maltose, mannitol, sucrose and xylose as electron donors. The main fermentation products from glucose metabolism were acetate, formate, butyrate and isobutyrate. The predominant cellular fatty acids were C(16:0) (68.4%) and C(14:0) (8.3%). The G+C content of the genomic DNA was 35.2 mol%. On the basis of its phylogenetic and physiological properties, a new genus and species, Defluviitalea saccharophila gen. nov., sp. nov., are proposed to accommodate strain LIND6LT2(T), placed in Defluviitaleaceae fam. nov. within the phylum Firmicutes, class Clostridia, order Clostridiales. Strain LIND6LT2(T) (=DSM 22681(T) =JCM 16312(T)) is the type strain of Defluviitalea saccharophila, which itself is the type species of Defluviitalea

A simple gas pressure manometer for measuring hydrogen production by hydrogenogenic cultures in serum bottles

International audienceThis study investigated the determination of hydrogen production by three H2-producing microorganisms (Thermotoga maritima, Thermococcus kodakarensis KOD1 and Enterobacter cloacae) cultured in 116-mL serum bottles. A gas pressure manometer was used to measure total pressure in the serum-bottle headspace. It was demonstrated that total pressure is the sum of the saturation pressure of water, the pressure expansion of gases, and the partial pressures of H2 () and CO2 (). A linear relationship was established between the partial pressure of H2 measured by gas chromatography and the sum of the partial pressures of H2 and CO2 measured by the manometer. When pH of culture medium was not controlled (pH decreased from 7 to 5), the ratio was close to stoichiometric H2/CO2 yield ratio of the most plausible metabolic pathways of each strain. values were 1.7, 1.9 and 0.9 for T. maritima, T. kodakarensis and E. cloacae, respectively. In these experimental conditions, can be deduced from total pressure measured by manometer

Microbial community structure associated with the high loading anaerobic codigestion of olive mill and abattoir wastewaters

International audienceThe effect of increasing the organic loading rates (OLRs) on the performance of the anaerobic codigestion of olive mill (OMW) and abattoir wastewaters (AW) was investigated under mesophilic and thermophilic conditions. The structure of the microbial community was also monitored. Increasing OLR to 9 g of chemical oxygen demand (COD) L−1 d−1 affected significantly the biogas yield and microbial diversity at 35 °C. However, at 55 °C digester remained stable until OLR of 12 g of COD L−1 d−1 with higher COD removal (80%) and biogas yield (0.52 L g−1 COD removed). Significant differences in the bacterial communities were detected between mesophilic and thermophilic conditions. The dominant phyla detected in the digester at both phases were the Firmicutes, Actinobacteria, Bacteroidetes, Synergistetes and Spirochaete. However, Verrucomicrobia, Proteobacteria and the candidate division BRC1 were only detected at thermophilic conditions. The Methanobacteriales and the Thermoplasmales were found as a high predominant archaeal member in the anaerobic sludge