A most-probable number technique for methanotrophic bacteria determination in biological reactors using methane as an electron donor for denitrification.

The most-probable number (MPN) technique along with methane uptake determinations were used to estimate the density of methanotrophic organisms in the biological reactors used for wastewater treatment. The experimental technique was conducted using serum bottles seeded with an inoculum taken from an aerobic sequencing batch reactor that used methane as the sole carbon source. To verify the presence ofmethanotrophic organisms in the support media, biomass samples were subjected to molecular cloning and sequencing techniques. When compared with the sequences published in databanks, the nucleotide sequences obtained showed a phylogenetic similarity of 98% to Methylomonas sp. (access number AF150792) and a phylogenetic similarity of 96% to Chryseobacterium sp. (access number AB264124), which are type I methanotrophs and denitrifiers, respectively.