Microbial communities responsible for fixation of CO₂ revealed by using <i>mcrA</i>, <i>cbbM</i>, <i>cbbL</i>, <i>fthfs</i>, <i>fefe-hydrogenase</i> genes as molecular biomarkers in petroleum reservoirs of different temperatures

Sequestration of CO2 in oil reservoir is one of the feasible options for mitigating atmospheric CO2 building up. The in situ bioconversion of sequestrated CO2 to methane by microorganisms inhabiting oil reservoirs is feasible. To evaluate the potential of in situ microbial fixation and conversion of CO2 into CH4 in oil reservoirs, a comprehensive molecular survey was performed to reveal microbial communities inhabiting four oil reservoirs with different temperatures by analysis of functional genes involved in the biochemical pathways of CO2 fixation and CH4 synthesis (cbbM, cbbL, fthfs, [FeFe]-hydrogenase encoding gene, and mcrA). A rich diversity of these functional genes was found in all the samples with both high and low temperatures and they were affiliated to members of the Proteobacteria (cbbL and cbbM, fthfs), Firmicutes and Actinobacteria (fthfs), uncultured bacteria ([FeFe]-hydrogenase), and Methanomirobiales, Methanobacteriales and Methanosarcinales (mcrA). The predominant methanogens were all identified to be hydrogenotrophic CO2-reducing physiological types. These results showed that functional microbial communities capable of microbial fixation and bioconversion of CO2 into methane inhabit widely in oil reservoirs, which is helpful to microbial recycling of sequestrated CO2 to further new energy in oil reservoirs.

In situ bioconversion of compactin to pravastatin by Actinomadura species in fermentation broth of Penicillium citrinum

The biocatalytic production of pravastatin from compactin by hydroxylation has found many applications in health care and pharmaceuticals. Actinomadura macra, Actinomadura madurae, and Actinomadura livida can efficiently bioconvert compactin to pravastatin. The fermentation broth (Penicillium citrinum fermented media) harvested on the eighth day contained 388.90 mg L−1 of compactin and an undetectable level of mycotoxin (citrinin). Bioconversion by A. macra was highest (87 %) in the yeast extract-amended medium. The anti-actinomadura effects of citrinin reduce the bioconversion capacity of Actinomadura. The in situ hydroxylation of compactin produced by P. citrinum represents a preferable alternative for the use of purified compactin, as a way to reduce cost and time processing.