Kazuhiro Fujiwara

Microbial diversity with dominance of 16S rRNA gene sequences with high GC contents at 74 and 98 °C subsurface crude oil deposits in Japan

We prepared DNA from the production waters of oil deposits and wellheads of the high- and hypertemperature Japanese oil wells #AR39 (depth, 1230 m; temperature, 74 °C; pressure, 2.92 MPa) and #SR123 (depth, 1687 m; temperature, 98 °C; pressure, 11.3 MPa) to detect indigenous bacterial and archaeal microorganisms. We used PCR to amplify the 16S rRNA genes of microbial communities and characterized them based on their sequences. A few species of microorganisms with high GC contents were detected in samples from oil deposits, whereas the microbial constituents and their GC contents were diverse in wellhead samples. A comparison of the composition of the microbial communities found that the predominant indigenous populations in the #SR123 oil deposit were Thermotoga hypogea-, Thermotoga petrophila- and Thermodesulfobacterium commune-like bacteria with a 61-63% GC content in their 16S rRNA gene sequences, and Archaeoglobus fulgidus-like archaea with a 65% GC content, whereas the major population in #AR39 comprised Thermacetogenium phaeum- and Fervidobacterium pennavorans-like bacteria and Methanothermobacter thermautotrophicus-like archaea with a 60%, 60% and 61% GC content, respectively.

Verification of Microbial Activities for Microbial Restoration of Methane Deposit With Subsurface CO2 Sequestration into the Depleted Oil Fields

The objective of this research is to estimate the possibility of microbial restoration of methane deposits using subsurface sequestered CO and indigenous anaerobes in depleted oil fields. The most important factors are the efficiency and velocity of methane conversion by indigenous anaerobes inhabiting a reservoir. Field samples (producing oil and water) from oil field in Japan were collected and analyzed in order to clarify the existence and survivability of indigenous methane-producing anaerobes under reservoir conditions. The hydrogenotrophic methanogen consortium MYH-4 consortium was separated from the enrichment culture added oil reservoir water. By using MYH-4 consortium, two experiments were conducted. (i)Direct calculation of the CO to methane conversion rate for economic assessment. (ii)As the main objective of the field operation test, it is necessary to identify the state of the subsurface injection environment and the limitations that it poses to methane production. To clarify this, the experiment was carried out by using stable isotope probing. At the result of these studies, it has been understood that the methane conversion efficiency from CO was approximately 50%.

Evaluation of the Influence That Was Produced by Phytoremediation of Soil Microorganisms at Oil Showings

土壌汚染が社会的に問題となっている中，コストと環境負荷が小さいファイトレメディエーションへの関心が高まっている．しかし，ファイトレメディエーションによる汚染物質の分解メカニズムには解明されていない部分が残されている．本研究では，長期間にわたって自然に原油が存在している油徴地帯から採取した土壌中の微生物群集に対してイタリアンライグラスが与える影響を評価した．原油資化微生物数，微生物活性及びＰＣＲ－ＤＧＧＥ法による微生物相解析を行うとともに，原油の含有量を経時的に評価した．この結果，イタリアンライグラス栽培土壌では，微生物相の改変が生じ，土壌微生物の活性が向上するとともに，原油資化性菌数が増加することが示された．また，このような微生物相の変化と対応して，栽培区の原油濃度が非栽培区に比べて有意に低下した．以上の結果から，植物の栽培によって生じた選択的な微生物相の改変が，土壌の原油濃度の低下に関与する可能性を示した．