Harnessing The Elements To Feed Microbes

The vast majority of fuels and chemicals used by humans are made from fossil carbon. Bioproduction from microorganisms, such as bacteria or yeast, might provide a way to wean us from our dependence on these unsustainable sources. In fact, microbes are already cultured at a huge scale across the planet ā€“ think breweries ā€“ and have been handled and processed by experts for centuries. Yet, in order to grow and produce a chemical of interest, microbes must be supplied with a suitable feedstock. What can we afford to feed them?

In recent years, the use of sugars as feedstock in biofactories has dramatically expanded. However, as the use of sugars for bioproduction increases, we begin to witness its drawbacks. First, sugar used by microbial biofactories cannot be used for food or feed. As our nutritional requirements continue to expand, diverting agricultural resources towards bioproduction become less sustainable and could severely decrease food security. Moreover, expanding agricultural land use for the sake of bioproduction reduces natural habitats and biodiversity and burdens the environment.

Alternative feedstocks, which do not compete with agricultural production, have been suggested, for example, lignocellulosic and algal biomass. However, the processing of these feedstocks is very challenging, necessitating costly and inefficient conversion methods. Even more important, the efficiency by which plants and algae intercept light and convert it into to biomass is very low, casting doubt on the very basic idea of harnessing this natural process to feed microbial bioproduction.

So what is the alternative? An ideal microbial feedstock would be directly derived from almost unlimited resources, fully available in the environment. To put it more poetically, we want to derive bioproduction from the “elements” of nature: air ā€“ from which we take carbon dioxide as a direct carbon source; water ā€“ which supplies the hydrogen equivalent; fire ā€“ the renewable energy, e.g., solar and wind, that provides the necessary driving force; and earth ā€“ representing the minerals, i.e., other elements, that are needed for microbial growth.

How do we feed these “elements” to microbes? In a recent paper, we investigated and compared different approaches to provide microbes with the carbon and energy they need for growth. From a point of view of energy, electricity provides a great starting point. While solar energy can be directly used to energize chemical processes, its conversion to electricity provides highly-needed flexibility. That is, when the sun doesnā€™t shine, the wind blows to drive turbines. If both are not available, hydro- or geo-energy could come to the rescue. Hence, by tapping into electricity as an energy source, we tap into a myriad of different renewable sources without being completely dependent on any.

Electricity can be used to transfer hydrogen equivalent from water to a chemical carrier. Microbes can then take the hydrogen equivalent from the carrier and use it to convert carbon dioxide into biomass and products. Several inorganic compounds, such as ions of iron or nitrate, can serve as such carriers. An even better approach is to use electricity to transfer hydrogen equivalent from water directly into carbon dioxide. The resulting reduced organic compound can be used as a microbial feedstock, “carrying” with it three of the required elements: carbon, hydrogen equivalent, and energy.

In our analysis, we show that carbon monoxide and formic acid, both one-carbon molecules, can serve as ideal intermediates between the former, chemical process, and the latter, biological conversion. However, while carbon monoxide is a toxic, flammable gas with low solubility, formic acid is completely soluble and easy to handle and transport. This makes formic acid an especially promising feedstock for bioproduction. Together, we envision a production chain which harnesses the advantages of each field: physicochemical processes support fast and efficient conversions of renewable energy into electricity and of carbon dioxide into formic acid, while biological processes are effective in converting this latter simple feedstock into a wide array of complex products.

It will take some time before we can fully implement this vision. Apart from further improvements in electrochemical processes, in order for the production chain to reach its full potential, we need to design and engineer better metabolic solutions for microbial growth on formic acid. While multiple microbes can grow on formic acid as sole carbon and energy source, most of the metabolic routes they employ for this growth are either limited in efficiency or are restricted to extreme conditions.

One of the main goals of our lab is to use engineering-like tools to design and implement novel metabolic routes that would support bioconversion of formic acid at very high efficiency and under non-extreme conditions. We are specifically working on engineering model microbes, widely used in the biotechnological industry for bioproduction processes, to grow on formic acid using the most efficient pathway we have designed so far: the reductive glycine pathway. Upon completion, these engineered microbes could pave the way for sustainable bioproduction of value-added chemicals from renewably-produced formic acid, and thus transform the way we produce our everyday commodities.

These findings are described in the article entitled,Ā Towards sustainable feedstocks: A guide to electron donors for microbial carbon fixation, recently published in the journalĀ Current Opinion in Biotechnology.

This work was funded by the European Commision and is part of theĀ EU consortium project called eForFuel. The work was conducted byĀ Nico JoannesĀ Claassens andĀ ArrenĀ Bar-Even from theĀ Max Planck Institute of Molecular Plant Physiology, andĀ IreneĀ SĆ”nchez-Andrea andĀ Diana ZitaĀ Sousa fromĀ Wageningen University. This research

About The Author

Arren Bar-Even

Arren is an Independent Research Group Leader at the Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm.

Speak Your Mind!


The Occurrence Of Eating Disorder Behaviors In The General Community

Published by Felipe Luz The University of Sydney and the CAPES Foundation, Ministry of Education of Brazil These findings are described in the article entitled An investigation of relationships between disordered eating behaviors, weight/shape overvaluation and mood in the general population, recently published in the journal Appetite (Appetite 129 (2018) 19-24). This work was conducted […]

Positive Vs. Negative Feedback Mechanisms

Positive and negative feedback mechanisms refer to any process that regulates the value of one variable in the face of another variable, thus increasing or decreasing the change in the value of the initial variable. In biology, feedback mechanisms are related to an organism maintainingĀ homeostasis. Homeostasis refers to the tendency of an organism to regulate […]

The Milky Way Galaxyā€™s Global Order And Mirror-Image Symmetry, Co-Rotation Radius, And The Local Incoming Mass

Can we “slice” a spiral arm into its components and order the slices? The Moon orbits around the Earth on a rough circle, the Earth orbits on a rough circle around the Sun, and the Sun orbits on a rough circle around the Center of our Galaxy known as the Milky Way. Gravitation is the […]

Sophisticated Family Planning In Malaria Parasites

Malaria parasites can tell good times from bad times and plan their offspring accordingly. The reproductive strategy these disease-causing parasites use is more sophisticated than previously thought and similar to that of more complex organisms like mammals, birds, insects, and plants. Malaria parasites (Plasmodium) are small blood parasites that are transmitted between hosts by mosquitoes. […]

What Attracts Mosquitoes To Humans?

Mosquitos are attracted to humans because we are a food source for them. Initially what attracts mosquitos are a combination of our exhalation of carbon dioxide, body heat, and smell. Mosquitos are more attracted to people with Type O blood and least attracted to Type A blood, based on several studies. You’ve probably heard that […]

Colchicine: The Cinderella Of Anticancer Drugs

Cancer is the second-most common cause of death in developed countries. The statistics suggest that, in the next 20 years, the number of global cancer cases will increase more than 50%, and the deaths caused by this disease will increase more than 60%, with respect to the current figures. Cancer appears when a group of […]

Novel Autonomous Biosampler Will Foster In Situ Aquatic Microbiome Monitoring

Climate change and the runoff of nutrients or pollutants greatly affects the equilibrium of natural microbial communities and compromises ecosystems’ environmental status. In order to effectively monitor these communities, thereā€™s a call for quick, low- cost, and efficient sampling methods. As a response to this demand, the recent study published in the scientific journal PLOS […]