Biological production of 2-propanol from propane using a metabolically engineered type I methanotrophic bacterium

Microbial oxidation of short-chain gaseous alkanes

Short-chain gaseous alkanes (SCGAs), including ethane, propane and butane, are major components of natural gas and their atmospheric emissions impact global air quality and tropospheric chemistry. Many microbial taxa can degrade SCGAs aerobically and anaerobically to CO2, acting as the major biological sink of these compounds and reducing their negative impacts on climate. Environmental metagenomics and cultivation efforts have expanded our understanding of SCGA-oxidizing microorganisms. In this Review, we discuss recent discoveries in the diversity, physiology and metabolism of aerobic and anaerobic SCGA-oxidizing microorganisms, highlight their climate implications and discuss how knowledge of these processes can help develop biotechnologies for environmental remediation and value-added chemical production.

Methanotrophic and heterotrophic co-cultures for the Polyhydroxybutyrate production by co-utilizing C1 and C3 gaseous substrates

Polyhydroxybutyrate (PHB) production using methanotrophs offers an economical solution to counter increasing environmental pollution. However, the substrate specificity of methanotrophs limits their ability to use multiple gases for chemical production. In this study, a synthetic heterotrophic and methanotrophic co-culture system was developed to co-utilize methane and propane for PHB production. First, a heterologous pathway was constructed in Escherichia coli BL21 (DE3) to produce PHB from acetone. Later, Methylocystis sp. OK1 produced acetone from propane; however, its PHB content decreased when methane and propane were co-utilized. Subsequently, the recombinant E. coli strain was co-cultured with Methylocystis sp. OK1 in the presence of methane and propane, which enhanced the PHB yield by 35%, 65%, and 100% with propane concentrations of 7% (v/v), 13% (v/v), and 20% (v/v), respectively, compared to the mono-cultures of Methylocystis sp. OK1. The results demonstrated PHB production in heterotrophic and methanotrophic co-cultures through co-utilization of methane and propane.

Methane to bioproducts: unraveling the potential of methanotrophs for biomanufacturing

With the continuous increase in the world population, anthropogenic activities will generate more waste and create greenhouse gases such as methane, amplifying global warming. The biological conversion of methane into biochemicals is a sustainable solution to sequester and convert this greenhouse gas. Methanotrophic bacteria fulfill this role by utilizing methane as a feedstock while manufacturing various bioproducts. Recently, methanotrophs have made their mark in industrial biomanufacturing. However, unlike glucose-utilizing model organisms such as Escherichia coli and Saccharomyces cerevisiae, methanotrophs do not have established transformation methods and genetic tools, making these organisms challenging to engineer. Despite these challenges, recent advancements in methanotroph engineering demonstrate great promise, showcasing these C1-carbon-utilizing microbes as prospective hosts for bioproduction. This review discusses the recent developments and challenges in strain engineering, biomolecule production, and process development methodologies in the methanotroph field.

Methanotrophs: Metabolic versatility from utilization of methane to multi-carbon sources and perspectives on current and future applications

The development of biorefineries for a sustainable bioeconomy has been driven by the concept of utilizing environmentally friendly and cost-effective renewable energy sources. Methanotrophic bacteria with a unique capacity to utilize methane as a carbon and energy source can serve as outstanding biocatalysts to develop C1 bioconversion technology. By establishing the utilization of diverse multi-carbon sources, integrated biorefinery platforms can be created for the concept of the circular bioeconomy. An understanding of physiology and metabolism could help to overcome challenges for biomanufacturing. This review summaries fundamental gaps for methane oxidation and the capability to utilize multi-carbon sources in methanotrophic bacteria. Subsequently, breakthroughs and challenges in harnessing methanotrophs as robust microbial chassis for industrial biotechnology were compiled and overviewed. Finally, capabilities to exploit the inherent advantages of methanotrophs to synthesize various target products in higher titers are proposed.