An Investigation into the Suitability of Sulfate-Reducing Bacteria as Models for Martian Forward Contamination

The NASA Planetary Protection policy requires interplanetary space missions do not compromise the target body for a current or future scientific investigation and do not pose an unacceptable risk to Earth, including biologic materials. Robotic missions to Mars pose a risk to planetary protection in the forms of forward and reverse contamination. To reduce these risks, a firm understanding of microbial response to Mars conditions is required. Sulfate-reducing bacteria are prime candidates for potential forward contamination on Mars. Understanding the potential for forward-contamination of sulfate-reducers on Mars calls for the characterization of sulfate-reducers under Mars atmosphere, temperature, and sulfate-brines. This study investigated the response of several sulfate-reducing bacteria, including spore formers and psychrophiles. The psychrophile Desulfotalea psychrophila was found to inconsistently survive positive control lab conditions, attributed to an issue shipping pure cultures. Desulfotomaculum arcticum, a spore-forming mesophilic sulfate-reducer, and Desulfuromusa ferrireducens, an iron and sulfate-reducer, were metabolically active under positive control lab conditions with complex and minimal growth medium. A wastewater treatment sulfate-reducing bacteria (SRB) isolate was subjected to sulfate + growth-medium solutions of varied concentrations (0.44 & 0.55% wt. SO42-). The wastewater SRB displayed higher cellular light-absorbance levels at delayed rates in 0.55% sulfate solutions, suggesting a greater total culture reproduction, but with increased lag time. Additional SRB were isolated from marine sediments, subjected to a shock pressure of 8.73 GPa, and returned to ideal conditions. The sulfate-concentration patterns in the impacted SRB culture suggests a destruction of culture occurred somewhere during the preparation process. The response of SRB in this investigation to Ca and Na sulfate-brines suggests that Martian sulfate deposits offer a viable energy sink to terrestrial microorganisms, and the studied SRB are capable of replication at reduced water-activity. Further investigation (i.e. sulfate cations and concentrations, temperature, pressure, etc.) may identify Martian locations at risk to forward contamination

Biotechnological aspects of sulfate reduction with methane as electron donor

Biological sulfate reduction can be used for the removal and recovery of oxidized sulfur compounds and metals from waste streams. However, the costs of conventional electron donors, like hydrogen and ethanol, limit the application possibilities. Methane from natural gas or biogas would be a more attractive electron donor. Sulfate reduction with methane as electron donor prevails in marine sediments. Recently, several authors succeeded in cultivating the responsible microorganisms in vitro. In addition, the process has been studied in bioreactors. These studies have opened up the possibility to use methane as electron donor for sulfate reduction in wastewater and gas treatment. However, the obtained growth rates of the responsible microorganisms are extremely low, which would be a major limitation for applications. Therefore, further research should focus on novel cultivation technique

Anaerobic degradation of dimethylsulfoniopropionate to 3-S-methylmercaptopropionate by a marine Desulfobacterium strain

Dimethylsulfoniopropionate, an osmolyte of marine algae, is thought to be the major precursor of dimethyl sulfide, which plays a dominant role in biogenic sulfur emission. The marine sulfate-reducing bacterium Desulfobacterium strain PM4 was found to degrade dimethylsulfoniopropionate to 3-S-methylmercaptopropionate. The oxidation of one of the methyl groups of dimethylsulfoniopropionate was coupled to the reduction of sulfate; this process is similar to the degradation of betaine to dimethylglycine which was described earlier for the same strain. Desulfobacterium PM4 is the first example of an anaerobic marine bacterium that is able to demethylate dimethylsulfoniopropionate.

Hydrometallurgy of the delta sulfide ores, second stage report

This report contains results of the Fluidized-Bed Leaching (FBL) initially adapted to improve Leaching-Flotation processing of Delta ores in sulfate solution. The research carried out in the continuous laboratory installation show, however, that the new, 3-phase (solid-liquid-gaseous) reactor also performs satisfactorily in other leaching systems. A new process of pyritic matrix destruction for precious metals recovery in the FBL reactor, and a new process for recovery of zinc and other metals in a chloride system are proposed on the basis of laboratory results.Submitted to: Nerco Minerals Compan

Pengolahan Logam Berat Khrom (Cr) Pada Limbah Cair Industri Penyamakan Kulit Dengan Proses Koagulasi Flokulasi Dan Presipitasi

Leather tannery industry waste water treatment research by coagulation flocculation and precipitation process has been carried out. The study aims to determine the treatment process with coagulant what is most optimum in removing the heavy metal content in leather tannery waste water, which includes coagulant lime, aluminum sulfate, and ferrous sulfate, and barium chloride, coagulant concentration, and pH optimum. Jar test result available optimum pH for coagulant lime at pH 8, for aluminum sulfate at pH 6, and for ferrous sulfate at pH 8. The optimum ratio of lime is 6,4; aluminum sulfate is 0,8; and ferrous sulfate is 0,48. The optimum concentration of barium chloride after treatment with lime, aluminum sulfate, and ferrous sulfate are 0,005; 0,043; and 0,005

Persistent sulfate formation from London Fog to Chinese haze

Sulfate aerosols exert profound impacts on human and ecosystem health, weather, and climate, but their formation mechanism remains uncertain. Atmospheric models consistently underpredict sulfate levels under diverse environmental conditions. From atmospheric measurements in two Chinese megacities and complementary laboratory experiments, we show that the aqueous oxidation of SO2 by NO2 is key to efficient sulfate formation but is only feasible under two atmospheric conditions: on fine aerosols with high relative humidity and NH3 neutralization or under cloud conditions. Under polluted environments, this SO2 oxidation process leads to large sulfate production rates and promotes formation of nitrate and organic matter on aqueous particles, exacerbating severe haze development. Effective haze mitigation is achievable by intervening in the sulfate formation process with enforced NH3 and NO2 control measures. In addition to explaining the polluted episodes currently occurring in China and during the 1952 London Fog, this sulfate production mechanism is widespread, and our results suggest a way to tackle this growing problem in China and much of the developing world

Rapid one-step separation and purification of recombinant phenylalanine dehydrogenase in aqueous two-phase systems

Background: Phenylalanine dehydrogenase (PheDH; EC 1.4.1.20) is a NAD +-dependent enzyme that performs the reversible oxidative deamination of L-phenylalanine to phenylpyruvate. It plays an important role in detection and screening of phenylketonuria (PKU) diseases and production of chiral intermediates as well. The main goal of this study was to find a simple and rapid alternative method for purifying PheDH. Methods: The purification of recombinant Bacillus sphaericus PheDH was investigated in polyethylene glycol (PEG) and ammonium sulfate aqueous two-phase systems (ATPS). The influences of system parameters including PEG molecular weight and concentration, pH and (NH4)2SO4 concentration on enzyme partitioning were also studied. The purity of enzyme was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Results: A single extraction process was developed for separation and purification of recombinant PheDH from E. coli BL21 (DE3). The optimized conditions for partitioning and purification of PheDH were 9% (w/w) PEG-6,000 and 16% (w/w) (NH4)2SO4 at pH 8.0. The partition coefficient, recovery, yield, purification factor and specific activity values were achieved 58.7, 135%, 94.42%, 491.93 and 9828.88 U/mg, respectively. Also, the Km values for L-phenylalanine and NAD+ in oxidative deamination were 0.21 and 0.13 mM, respectively. Conclusion: The data presented in this paper demonstrated the potential of ATPS as a versatile and scaleable process for downstream processing of recombinant PheDH

Method for the preparation of thin-skinned asymmetric reverse osmosis membranes and products thereof

A method for preparing water insoluble asymmetric membranes from water soluble polymers is discussed. The process involves casting a film of the polymer, partially drying it, and then contacting it with a concentrated solution of a transition metal salt. The transition metal ions render the polymer insoluable and are believed to form a complex with it. Optionally, the polymer is crosslinked with heat or radiation. The most preferred polymer is poly(vinyl alcohol). The most preferred complexing salt is copper sulfate. The process and the metal ion linked membranes are discussed. The membranes are reverse osmosis membranes

Improved ceramic heat exchange material

Improved corrosion resistant ceramic materials that are suitable for use as regenerative heat exchangers for vehicular gas turbines is reported. Two glass-ceramic materials, C-144 and C-145, have superior durability towards sulfuric acid and sodium sulfate compared to lithium aluminosilicate (LAS) Corning heat exchange material 9455. Material C-144 is a leached LAS material whose major crystalline phase is silica keatite plus mullite, and C-145 is a LAS keatite solid solution (S.S.) material. In comparison to material 9455, material C-144 is two orders of magnitude better in dimensional stability to sulfuric acid at 300 C, and one order of magnitude better in stability to sodium sulfate at 1000 C. Material C-145 is initially two times better in stability to sulfuric acid, and about one order of magnitude better in stability to sodium sulfate. Both C-144 and C-145 have less than 300 ppm delta L/L thermal expansion from ambient to 1000 C, and good dimensional stability of less than approximately 100 ppm delta L/L after exposure to 1000 C for 100 hours. The glass-ceramic fabrication process produced a hexagonal honeycomb matrix having an 85% open frontal area, 50 micrometer wall thickness, and less than 5% porosity

Combustion system processes leading to corrosive deposits

Degradation of turbine engine hot gas path components by high temperature corrosion can usually be associated with deposits even though other factors may also play a significant role. The origins of the corrosive deposits are traceable to chemical reactions which take place during the combustion process. In the case of hot corrosion/sulfidation, sodium sulfate was established as the deposited corrosive agent even when none of this salt enters the engine directly. The sodium sulfate is formed during the combustion and deposition processes from compounds of sulfur contained in the fuel as low level impurities and sodium compounds, such as sodium chloride, ingested with intake air. In other turbine and power generation situations, corrosive and/or fouling deposits can result from such metals as potassium, iron, calcium, vanadium, magnesium, and silicon