Climate change involves shifts in global or regional climate patterns. A major contributor to climate change is the presence of atmospheric greenhouse gases including carbon dioxide, methane, and nitrous oxide. High concentrations of these gases have led to an increase in temperatures, changes in wet/dry cycles, droughts, extreme frost and heatwaves, heavy rainfall and storms, and increased fire frequency.
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Human consumption in several sectors including food supply, energy, transportation, and livestock has increased atmospheric greenhouse gas levels. Therefore, these processes have significantly contributed to climate change over the decades. As a result, climate change has become one of the greatest socio-scientific issues faced where global temperatures are reported to increase more than 2 °C by 2050.
Due to the severity of this issue, scientists are committed to discovering ways to solve climate change, one of which involves the use of microbes. The specific ways in which microbes can be utilized to mitigate climate change involve greenhouse gas sequestration and sustainable next-generation biofuel production.
Using microbes for carbon sequestration:
Soil is classified as the largest carbon reservoir. Naturally, carbon is captured into the soil as carbon dioxide through plant photosynthesis and organism decomposition. This process of removing atmospheric carbon dioxide and increasing soil organic carbon storage is known as carbon sequestration. Scientists aim to reduce carbon emissions to solve climate change through the use of soil microbial inoculants that promote carbon sequestration.
Soil microbes such as growth-promoting bacteria and fungi have proven to sequester carbon into the soil. Through this process, microbes are able to reduce atmospheric carbon dioxide and therefore can be utilized to tackle the issue of climate change. This may be achieved through the introduction of environmentally friendly microbial formulations with carbon-sequestering ability to agricultural soil.
Various soil microbes contribute to carbon sequestration through different mechanisms. A few of these mechanisms include metabolic activities that capture carbon dioxide, form vegetative tissues and products, form soil aggregates, and also possess the ability to sediment carbonates. Furthermore, microbes vary in how efficiently they sequester carbon.
For instance, certain microbes possess faster metabolic rates and therefore sequester carbon quicker. The diversity in mechanisms and efficiency provides the possibility of using specific microbes for particular lands for greater benefits.
Despite their proven ability to sequester atmospheric carbon dioxide into the soil, there are limited studies focused on using microbial inoculants as a carbon-sequestering technique to solve climate change. Therefore, greater efforts and studies are required to determine how effective this technique could be to mitigate climate change.
Using microbes to reduce methane emissions:
Methane is another atmospheric greenhouse gas that contributes to climate change and in fact, is more potent than carbon dioxide. Significant amounts of methane are produced by human activity including the use of fossil fuels and landfills. Therefore, scientists are also dedicating studies to reduce methane emissions through the use of microbes.
Bacteria known as methanotrophs were first discovered in Arctic mineral soils. They are also typically found in environments such as hot springs and mud pots. Methanotrophs use methane for metabolism as a primary energy source, thus making them a unique type of bacteria. Methanotrophs can use methane as an energy source due to the presence of enzymes known as methane monooxygenases. Furthermore, methanotrophs possess high affinity and therefore are extremely efficient in consuming methane.
It has been estimated that approximately 40-60% of the methane produced is consumed by methanotrophs in wetland environments. Due to this, methanotrophs have been gaining increasing attention as the issues of climate change worsens; leading to hundreds of studies dedicated to these microbes over the last two decades. The aim is to use methanotrophs as biocatalysts in agricultural soil and landfills, ultimately leading to a reduction in atmospheric methane levels.
Using microbes to produce sustainable biofuels:
Although the use of fossil fuels acts as a major energy source, this process of generating energy releases greenhouse gases and therefore also contributes to climate change. As a result, scientists are now investigating the ability of microbes to use renewable resources for the production of next-generation sustainable biofuels, thus maintaining energy supplies whilst also solving climate change. Biofuels include fuels that are produced by renewable resources via biological processes.
Multiple studies have confirmed the ability of microbes to produce biofuels through biological pathways. Since all microbes including bacteria, fungi, and microalgae possess metabolic diversity, various microbes use different substrates as the starting point for biofuel synthesis. For instance, cellulolytic organisms such as Clostridium thermocellum can utilize energy from plant-derived lignocellulose to create biofuels.
In contrast, photosynthetic organisms including microalgae and cyanobacteria make use of carbon dioxide as an energy source to generate biofuels. Finally, as mentioned previously methanotrophs consume methanol as an energy source, thus allowing them to induce biological processes required to generate biofuels.
A challenge faced when attempting to use microbes for sustainable biofuel synthesis is the efficiency of the microbiological pathways. Based on current pathways, the productivity and yield of biofuel production by microbes is far too low to justify industrial applications. Scientists are attempting to address these issues through redesigning and engineering existing metabolic systems as well as trying to discover novel enzymes, microbes, and pathways to improve productivity and yield.
References:
- Abatenh, E., Gizaw, B., Tsegaye, Z., Tefera, G. (2018). Microbial Function on Climate Change – A Review. Open J Environ Biol. 3: 001-007.
- Ahmed, A., Odelade, K., Babalola, O. (2019). Microbial Inoculants for Improving Carbon Sequestration in Agroecosystems to Mitigate Climate Change. Chapters 1-3.
- Hakobyan, A., Liesack, W. (2020). Unexpected metabolic versatility among type II methanotrophs in the Alphaproteobacteria. Biol. Chem. 401: 1469-1477.
- Ho, A., Kwon, M., Horn, M. (2019). Environmental Applications of Methanotrophs. Microbiology Monographs. 32: 231-255.
- Liao, J., Mi, L., Pontrelli, S., Luo, S. (2016). Fuelling the future: microbial engineering for the production of sustainable biofuels. Nature Reviews Microbiology. 14: 288-304.
- Widiyawati, Y. (2020). Global warming & climate change: integration of socio-scientific issues to enhance scientific literacy. Journal of Physics. 1511: 1-11.
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