Enrichment Cultures Of Microorganisms Research Articles

Simultaneous methanogenesis and acetogenesis from the greenhouse carbon dioxide by an enrichment culture supplemented with zero-valent iron

Abstract The microbial reduction of CO2 into value-added products is gaining considerable attention and can play a significant role in the field of environment and energy research. A novel strategy for biotransformation of CO2 was tested with zero valent iron (ZVI) and enrichment cultures for methane and acetate production under anaerobic conditions at room temperature. The favorable performance of CO2 conversion (81.67% of conversion rate) was achieved in ZVI-amended treatments by enhanced methanogenesis and acetogenesis simultaneously. The enrichment consortium of microorganisms containing Methanosarcina spp. and Clostridiaceae was responsible for methane and acetate production, and accounted for 25.89% and ∼4.83% of CO2 conversion, respectively. Scanning electron microscopy (SEM) observation and mass balance analysis of hydrogen detected in the headspace indicated that direct electron transfer and utilization possibly occurred with these microbes, especially methanogens. Interestingly, X-ray Photoelectron Spectroscopy (XPS) confirmed carbonation mineral (FeCO3) as the major strategy of CO2 consumption under the experimental conditions. These observations collectively revealed that supplementation of ZVI can be a favorable electron donor to stimulate and accelerate the biotransformation of CO2 into methane and acetate by the enrichment culture of microorganisms, and the information presents available alternative biochemical pathways for energy recovery from greenhouse gas under anaerobic conditions.

Construction Biotechnology: a new area of biotechnological research and applications.

A new scientific and engineering discipline, Construction Biotechnology, is developing exponentially during the last decade. The major directions of this discipline are selection of microorganisms and development of the microbially-mediated construction processes and biotechnologies for the production of construction biomaterials. The products of construction biotechnologies are low cost, sustainable, and environmentally friendly microbial biocements and biogrouts for the construction ground improvement. The microbial polysaccharides are used as admixtures for cement. Microbially produced biodegradable bioplastics can be used for the temporarily constructions. The bioagents that are used in construction biotechnologies are either pure or enrichment cultures of microorganisms or activated indigenous microorganisms of soil. The applications of microorganisms in the construction processes are bioaggregation, biocementation, bioclogging, and biodesaturation of soil. The biotechnologically produced construction materials and the microbially-mediated construction technologies have a lot of advantages in comparison with the conventional construction materials and processes. Proper practical implementations of construction biotechnologies could give significant economic and environmental benefits.

Characterization of the aerobic hydrocarbon-oxidizing enrichments from a high-temperature petroleum reservoir by comparative analysis of DNA- and RNA-derived clone libraries

Enrichment cultures of aerobic hydrocarbon-oxidizing bacteria obtained from the injection and production wells of the Dagang oil field (China) were studied by molecular biological and microbiological methods. This work is the first to report simultaneous isolation of DNA and RNA from enrichment cultures of microorganisms from oil strata with further construction of clone libraries of 16S rRNA genes and 16S crDNA (complementary rDNA). Comparative analysis of the DNA- and RNA-derived clone libraries made it possible to determine the total genomic diversity of microorganisms, as well as to reveal metabolically active microorganisms in these cultures. Phylotypes of bacteria of the genus Geobacillus were found to be dominant in the DNA and RNA clone libraries of the enrichment cultures from the production well. Phylotypes of bacteria belonging to Geobacillus, Pseudomonas, Tepidiphilus, and other genera were detected in the DNA and RNA libraries obtained from the culture from the injection well. Phylotypes of bacteria of the genus Geobacillus were predominant in the RNA library and represented the second-largest group (after pseudomonads) in the DNA library. In the RNA libraries of the alkB genes of both enrichments, three homologs close to alkB-geo1, alkB-geo2, and alkB-geo4 of bacteria of the genus Geobacillus were detected. The occurrence pattern of the alkB transcripts, ribosomal RNA, and the 16S rRNA genes of bacteria of the genus Geobacillus indicates the predominance and functional activity of geobacilli in the enrichment cultures of hydrocarbon-oxidizing bacteria from high-temperature petroleum reservoir.

Bacteria-epiphytes of brown macro alga in oil utilization in north sea ecosystems

Using the luminescent microscopy method, an epiphytic microbial community of Fucus sp. sea macrophytes collected in the littoral zone of White Sea was investigated. The abundant colonization of macrophytes’ surface by various bacteria, yeast, and microscopic alga was revealed. Enrichment culture of microorganisms—active oxidesers of oil and its derivatives was obtained with using of fucus’ thallus fragments. In macrocosm experiments on a biological research station of Moscow State University (MSU) at the coast of White Sea at the conditions imitating that of nature, the high oxidizing ability of selected cultures of the epiphytic microbial community was demonstrated. It was shown that the rate of oil utilization depends on its concentration and amount of epiphytic microbial community biomass used for this process.

Distribution and activity of microorganisms in the deep repository for liquid radioactive waste at the Siberian Chemical Combine

The physicochemical conditions, composition of microbial communities, and the rates of anaerobic processes in the deep sandy horizons used as a repository for liquid radioactive wastes (LRW) at the Siberian Chemical Combine (Seversk, Tomsk oblast), were studied. Formation waters from the observation wells drilled into the production horizons of the radioactive waste disposal site were found to be inhabited by microorganisms of different physiological groups, including aerobic organotrophs, anaerobic fermentative, denitrifying, sulfate-reducing, and methanogenic bacteria. The density of microbial population, as determined by cultural methods, was low and usually did not exceed 10(4) cells/ml. Enrichment cultures of microorganisms producing gases (hydrogen, methane, carbon dioxide, and hydrogen sulfide) and capable of participation in the precipitation of metal sulfides were obtained from the waters of production horizons. The contemporary processes of sulfate reduction and methanogenesis were assayed; the rates of these terminal processes of organic matter destruction were found to be low. The denitrifying bacteria from the underground repository were capable of reducing the nitrates contained in the wastes, provided sources of energy and biogenic elements were available. Biosorption of radionuclides by the biomass of aerobic bacteria isolated from groundwater was demonstrated. The results obtained give us insight into the functional structure of the microbial community inhabiting the waters of repository production horizons. This study indicates that the numbers and activity of microbial cells are low both inside and outside the zone of radioactive waste dispersion, in spite of the long period of waste discharge.

Formation and structure of granulated microbial aggregates used in aerobic wastewater treatment

Granular microbial aggregates are used in aerobic treatment of wastewater. The granules have diverse microbial community and complex spatial structure. The structural elements are radial sub-aggregates, concentric layers, channels, pores, polysaccharide plugs, and an anaerobic core of lysed cells. Aerobic bacteria, consisting of 69–84% of microbial biomass, were concentrated in a layer to the depth of 550 μm from the surface of the granule. Facultative anaerobic bacteria, consisting of 9–13% of microbial biomass, dominated in a layer at a depth from 550 μm to 850 μm from the surface of the granule. Obligate anaerobic bacteria, consisting of 2% of microbial biomass, dominated in a layer on the depth from 850 μm to 1,000 μm from the surface of the granule. A core of dead and lysed cells was at a depth greater than 1,000 μm from the surface of the granule. The depth of the anaerobic layer correlated with the appearance of polysaccharide plugs in the pores. Enrichment cultures of microorganisms with high cell surface hydrophobicity or self-aggregation ability can be used to facilitate the formation of microbial granules.