Bacteria found in northern aquatic ecosystems convert methane into bio-based raw material

Nordic lakes and peatlands are home not only to fish, plants and other organisms but also to bacteria that feast on methane, which is formed in the anaerobic conditions at the bottom where organic matter is being decomposed. Methane being a potent greenhouse gas, they are helping to combat climate change. The Bio and Circular Economy research group at Tampere University studies these bacteria that are called methanotrophs, meaning “methane eaters”.

“Methanotrophs devour methane to grow. In circular economy solutions, they can be used to convert methane contained in biogas into bio-based products,” says Antti Rissanen, postdoctoral researcher who leads the study at Tampere University.

The research conducted on methanotrophs at Tampere University is an important part of the global efforts to find new circular economy solutions for harnessing the potential of biogas, which is generated as a by-product in the treatment of agricultural and residential waste and wastewater.  

“The methane contained in biogas is a cheap and plentiful raw material that could be captured to curb climate change and reduce the use of natural resources without competing with food production,” Antti Rissanen adds.

Bacteria-based animal feed and raw materials for industry

Methanotrophs are already commercially utilised around the world, for example, as animal feed. The biomass consisting of bacteria that dine on methane can be used to feed livestock, fish in particular. This alternative source of protein could replace animal protein – such as fish meal and crustacean meal – in livestock nutrition. The researchers at Tampere University are also interested in the chemicals secreted by methanotrophs.

“Based on the DNA sequencing of environmental samples, we already know that methanotrophs found in lakes and peatlands are capable of converting methane, for example, into organic acids which can then be used as industrially important platform chemicals that serve as starting materials for the manufacture of various products,” Rissanen notes.

“We fed the organic acids produced by methanotrophs to non-methanotrophic bacteria that converted them into 1-undecene, which is an important industrial chemical,” says postdoctoral researcher Ramita Khanongnuch who is among the researchers taking part in the study.

DNA sequencing reveals the genome of methane-eating bacteria

To study the conversion of methane into bio-based products under controlled laboratory conditions, the researchers had to first isolate methanotrophs from their natural environment. They collected samples from boreal lakes located in Lammi and Evo in Hämeenlinna, Finland. Previous studies carried out in Finland have shown that boreal lakes are rich in methanotrophs. In addition to the three species of methanotrophs isolated from the samples, the researchers had access to two species isolated from peatlands located in Svalbard, Norway.

“As the isolation of pure cultures of methanotrophs from samples is a painstaking process that took an entire year, we also conducted experiments on methanotrophs that had already been isolated,” Ramita Khanongnuch says.

The researchers have already succeeded in demonstrating in a laboratory setting that methanotrophs found in lakes and peatlands produce organic acids from methane. They have also unravelled the genome of the methanotrophic strains isolated from the samples, which enables an even more in-depth investigation of their behaviour and ability to produce different substances. Future studies will also focus on increasing the efficiency of converting methane into bio-based products.

The study funded by Kone Foundation and the Academy of Finland was launched in early 2019 and will continue until the end of August 2022. The researchers are currently busy writing research papers. During the study, they have employed basic methods for culturing and isolating bacteria, conducted measurements with gas chromatography, high-performance liquid chromatography and mass spectrometry systems as well as studied the identity and functional abilities of different methanotrophic strains living in natural and laboratory environments with the help of so-called next-generation DNA sequencing technologies.  

The study has been carried out in collaboration with the Arctic University of Norway (Tromsø, Norway), the Swedish University of Agricultural Sciences (Uppsala, Sweden), the MARUM - Center for Marine Environmental Sciences at the University of Bremen (Germany) and the universities of Helsinki,  Eastern Finland and Jyväskylä (Finland). The supercomputer Puhti housed at the IT Centre for Science (CSC) in Finland was deployed in the analysis of sequencing data.

Read more about research in the field:

• Oxford Academic: Vertical stratification patterns of methanotrophs and their genetic controllers in water columns of oxygen-stratified boreal lakes.
• Frontiers: Candidatus Methylumidiphilus Drives Peaks in Methanotrophic Relative Abundance in Stratified Lakes and Ponds Across Northern Landscapes.
• BioRxiv: A two-staged bacterial process coupling methanotrophic and heterotrophic bacteria for 1-alkene production from methane.
• Science Direct : Draft genome sequence data of methanotrophic Methylovulum psychrotolerans strain S1L and Methylomonas paludis strain S2AM isolated from hypoxic water column layers of boreal lakes.

Further information

Antti Rissanen
antti.rissanen [at] tuni.fi

Ramita Khanongnuch
ramita.khanongnuch [at] tuni.fi

Rahul Mangayil
rahul.mangayil [at] tuni.fi