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Development of a novel methanotrophic process with the helper micro‐organism Hyphomicrobium sp. NM3

Jeong, S.‐Y., Kim, T.G.
Journal of applied microbiology 2019 v.126 no.2 pp. 534-544
Hyphomicrobium, Methylocystis, biomass, bioreactors, coculture, dialysis, methane, methanotrophs, oxidation, quantitative polymerase chain reaction, reverse transcriptase polymerase chain reaction, washing
AIMS: Microbial consortia can be more efficient at biological processes than single isolates. The purposes of this study were to design and evaluate a synthetic microbial consortium containing the methanotroph Methylocystis sp. M6 and the helper Hyphomicrobium sp. NM3, and develop a novel methanotrophic process for this consortium utilizing a dialysis membrane. METHODS AND RESULTS: Hyphomicrobium increased the methane‐oxidation rate (MOR), biomass and stability at a dilution rate of 0·067 day⁻¹ in fed‐batch co‐culture. qRT‐PCR showed that Methylocystis population increased gradually with time, whereas Hyphomicrobium population remained stable despite cell washing, confirming synergistic population interaction. At 0·1 day⁻¹, spiking of Hyphomicrobium effectively increased the methanotrophic activity, after which Hyphomicrobium population decreased with time, indicating that the consortium is optimal at <0·1 day⁻¹. When Hyphomicrobium was grown in dialysis membrane within the bioreactor, MOR increased linearly up to 155·1 ± 1·0 mmol l⁻¹ day⁻¹ at 0·067, 0·1, 0·2 and 0·4 day⁻¹, which is the highest observed value for a methanotrophic reactor. CONCLUSIONS: Hyphomicrobium sp. NM3 is a promising helper micro‐organism for methanotrophs. Hyphomicrobium‐methanotroph consortia used concurrently with existing methods can produce an efficient and stable methane oxidation system. SIGNIFICANCE AND IMPACT OF THE STUDY: This novel methanotrophic process is superior to those previously reported in the literature, and can provide efficient and stable methane oxidation.