Carbon Monoxide, Hydrogen, and Formate Metabolism during Methanogenesis from Acetate by Thermophilic Cultures of Methanosarcina and Methanothrix Strains

ArticleinApplied and Environmental Microbiology 58(10):3323-9 · November 1992with21 Reads
Source: PubMed
Abstract
CO and H(2) have been implicated in methanogenesis from acetate, but it is unclear whether they are directly involved in methanogenesis or electron transfer in acetotrophic methanogens. We compared metabolism of H(2), CO, and formate by cultures of the thermophilic acetotrophic methanogens Methanosarcina thermophila TM-1 and Methanothrix sp. strain CALS-1. M. thermophila accumulated H(2) to partial pressures of 40 to 70 Pa (1 Pa = 0.987 x 10 atm), as has been previously reported for this and other Methanosarcina cultures. In contrast, Methanothrix sp. strain CALS-1 accumulated H(2) to maximum partial pressures near 1 Pa. Growing cultures of Methanothrix sp. strain CALS-1 initially accumulated CO, which reached partial pressures near 0.6 Pa (some CO came from the rubber stopper) during the middle of methanogenesis; this was followed by a decrease in CO partial pressures to less than 0.01 Pa by the end of methanogenesis. Accumulation or consumption of CO by cultures of M. thermophila growing on acetate was not detected. Late-exponential-phase cultures of Methanothrix sp. strain CALS-1, in which the CO partial pressure was decreased by flushing with N(2)-CO(2), accumulated CO to 0.16 Pa, whereas cultures to which ca. 0.5 Pa of CO was added consumed CO until it reached this partial pressure. Cyanide (1 mM) blocked CO consumption but not production. High partial pressures of H(2) (40 kPa) inhibited methanogenesis from acetate by M. thermophila but not by Methanothrix sp. strain CALS-1, and 2 kPa of CO was not inhibitory to M. thermophila but was inhibitory to Methanothrix sp. strain CALS-1. Levels of CO dehydrogenase, hydrogenase, and formate dehydrogenase in Methanothrix sp. strain CALS-1 were 9.1, 0.045, and 5.8 mumol of viologen reduced min mg of protein. These results suggest that CO plays a role in Methanothrix sp. strain CALS-1 similar to that of H(2) in M. thermophila and are consistent with the conclusion that CO is an intermediate in a catabolic or anabolic pathway in Methanothrix sp. strain CALS-1; however, they could also be explained by passive equilibration of CO with a metabolic intermediate.
    • "Obligate aceticlastic methanogens such as Methanothrix sp. strain CALS-1, were observed to accumulate CO to low partial pressures while metabolizing acetate (Zinder and Anguish, 1992). Upon addition of low amounts of CO, it was consumed till equilibrium levels of 0.16 Pa. "
    [Show abstract] [Hide abstract] ABSTRACT: Carbon monoxide can act as a substrate for different modes of fermentative anaerobic metabolism. The trait of utilizing CO is spread among a diverse group of microorganisms, including members of bacteria as well as archaea. Over the last decade this metabolism has gained interest due to the potential of converting CO-rich gas, such as synthesis gas, into bio-based products. Three main types of fermentative CO metabolism can be distinguished: hydrogenogenesis, methanogenesis, and acetogenesis, generating hydrogen, methane and acetate, respectively. Here, we review the current knowledge on these three variants of microbial CO metabolism with an emphasis on the potential enzymatic routes and bio-energetics involved.
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    • "With the increase of ZVSI, the yield of H 2 increased and reached the greatest of 12.3 ± 1.5 mL at 1.0 g-ZVSI/g VSS. It was reported previously that high H 2 content (or partial pressure) was detrimental to methane production [29] because of the associated CO production [48] and/or the impeded thermodynamical conversions of propionate and butyrate into acetate [31], which inhibited acetoclastic methanogenesis (Methanosaeta and Methanosarcina [29]). Notably, H 2 did not accumulate continuously herein even at the highest dosage of ZVSI 1.0 g/g VSS, but was quickly consumed during the following biological process (especially at 35 °C), during which no H 2 was detected. "
    [Show abstract] [Hide abstract] ABSTRACT: The use potential of zero valent scrap iron (ZVSI) for promoting anaerobic production of waste activated sludge (WAS) was assessed. The results indicated that the presence of ZVSI effectively enhanced WAS methane production. Methane yield reached the maximum of 174.9 +/- 1.5 mL/g VSSfed with addition of 1.0 g-ZVSI/g VSS, increasing by 38.3%. The corresponding values for sludge hydrolysis (%H), acidogenesis (%A), and methanogenesis rate (%M) increased into 52.6 +/- 0.4%, 44.5 +/- 2.9% and 40.8 +/- 0.3%, respectively, versus 45.2 +/- 0.5%, 40.9 +/- 2.0% and 29.5 +/- 0.2% in the test without ZVSI. Further investigations confirmed that ZVSI could offer electrons (H-2/[H]), promote H-2 consumption and afford beneficial pH environment for WAS digestion, which stimulated the metabolisms of critical microbes involved in the process and, subsequently accelerated the hydrolysis-acidification-methanation steps of WAS. As a result of this, methane production was upgraded. The superior ability of ZVSI to serve as a source of electron donors will open a new door for WAS treatment. Moreover, ZVSI is less expensive, and convenient to use, providing a cost-efficient alternative for simultaneous energy recovery along with waste iron scrap conservation.
    Full-text · Article · Nov 2014
    • "With the increase of ZVSI, the yield of H 2 increased and reached the greatest of 12.3 ± 1.5 mL at 1.0 g-ZVSI/g VSS. It was reported previously that high H 2 content (or partial pressure) was detrimental to methane production [29] because of the associated CO production [48] and/or the impeded thermodynamical conversions of propionate and butyrate into acetate [31], which inhibited acetoclastic methanogenesis (Methanosaeta and Methanosarcina [29]). Notably, H 2 did not accumulate continuously herein even at the highest dosage of ZVSI 1.0 g/g VSS, but was quickly consumed during the following biological process (especially at 35 °C), during which no H 2 was detected. "
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    G ZhenG ZhenX LuX LuYY LiYY Li+1 more author ...Y ZhaoY Zhao
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