Journal of Environmental Biology

Contributions of available substrates and activities of trophic microbial community to methanogenesis in vegetative and reproductive rice rhizospheric soil

Sansanee Chawanakul^1,3, Pawinee Chaiprasert*², Sirintornthep Towprayoon¹  and Morakot Tanticharoen⁴

¹The Joint Graduate School of Energy and Environment (JGSEE), King Mongkut’s University of Technology, Thonburi, 126 Pracha Utit Rd., Thung Khru, Bangkok 10140, Thailand

²School of Bioresources and Technology, King Mongkut’s University of Technology, Thonburi,         

83 Moo 8, Thakham, Bangkhuntien, Bangkok 10150, Thailand

³Department of Biological Science, Faculty of Science, Ubon Ratchathani University,

Warin Chamrab District, Ubon Ratchathani. 34190, Thailand

⁴National Center for Genetic Engineering and Biotechnology (BIOTEC), 113 Thailand Science Park,

Klong Luang, Pathumthani 12120, Thailand

(Received: April 05, 2008; Revised received: July 05, 2008; Accepted:August 28, 2008)

Abstract: Potential of methane production and trophic microbial activities at rhizospheric soil during rice cv. Supanburi 1 cultivation were determined by laboratory anaerobic diluents vials. The methane production was higher from rhizospheric than non-rhizospheric soil, with the noticeable peaks during reproductive phase (RP) than vegetative phase (VP). Glucose, ethanol and acetate were the dominant available substrates found in rhizospheric soil during methane production at both phases. The predominance activities of trophic microbial consortium in methanogenesis, namely fermentative bacteria (FB), acetogenic bacteria (AGB), acetate utilizing bacteria (AB) and acetoclastic methanogens (AM) were also determined. At RP, these microbial groups were enhanced in the higher of methane production than VP. This correlates with our finding that methane production was greater at the rhizospheric soil with the noticeable peaks during RP (1,150 ± 60 nmol g dw^-1 d^-1) compared with VP (510 ± 30 nmol g dw^-1 d^-1). The high number of AM showed the abundant (1.1x10⁴ cell g dw^-1) with its high activity at RP, compared to the less activity with AM number at VP (9.8x10² cell g dw^-1). Levels of AM are low in the total microbial population, being less than 1% of AB. These evidences revealed that the microbial consortium of these two phases were different. 

Key words: Acetoclastic methanogens, Methane production, Rice rhizospheric soil, Trophic microbial consortium

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