29 November 2023

‘Protected’ bacteria replace chemical fertilizers


MIT scientists have developed a coating to protect and ‘package’ bacteria, making them transportable from the production lab to the field. Where they become an alternative to fertilizers

by Matteo Cavallito


Is it possible to replace chemical fertilizers with bacteria? Can microorganisms and their soil services be used, thereby reducing the climate impact of synthetics? Yes, explain some American researchers. Provided, however, we can solve a logistical problem: “packaging” the bacteria to preserve their integrity and turning them into a product capable of being shipped to farms.

Bacteria are an effective alternative

Chemical fertilizer production is responsible for about 1.5 percent of global greenhouse gas emissions, Massachusetts Institute of Technology (MIT) researchers explained in a statement released in recent weeks. Bacteria that can convert nitrogen gas to ammonia “could not only provide nutrients that plants need, but also help regenerate soil and protect plants from pests.”

The problem, however, is that these microorganisms “are sensitive to heat and humidity, so it’s difficult to scale up their manufacture and ship them to farms.” To solve the problem, MIT chemists devised a metallorganic coating that protects bacterial cells from damage without impeding their growth or function. According to a study, they found that these coated bacteria improve the germination rate of a variety of seeds, including corn seeds.

A special coating

According to Ariel Furst, professor of chemical engineering at MIT and lead author of the study, the coating could make it much easier for farmers to use microbes as fertilizers. In the investigation, researchers created 12 different “nets” to encapsulate Pseudomonas chlororaphis, a nitrogen-fixing bacterium that protects plants from harmful fungi and other pests.

The coatings contain two components – a metal and an organic substance called polyphenol – that can self-assemble into a protective shell.

“The metals used for the coatings, including iron, manganese, aluminum, and zinc, are considered safe as food additives,” the statement explains. “Polyphenols, which are often found in plants, include molecules such as tannins and other antioxidants.” Because of these components, the nets can protect microbes. In this way, bacteria can be distributed much more easily and with less cost.

Fonte: Burke et al., "Self-Assembled Nanocoatings Protect Microbial Fertilizers for Climate-Resilient Agriculture", Journal of the American Chemical Society, 30 ottobre 2023 CC BY-NC-ND 4.0 DEED Attribution-NonCommercial-NoDerivs 4.0 International https://pubs.acs.org/doi/10.1021/jacsau.3c00426

Source: Burke et al., “Self-Assembled Nanocoatings Protect Microbial Fertilizers for Climate-Resilient Agriculture”, Journal of the American Chemical Society, October 30th 2023 CC BY-NC-ND 4.0 DEED Attribution-NonCommercial-NoDerivs 4.0 International

The research

The bacterium examined can be used as a substitute for fertilizers but proves to be rather delicate at the same time. “It is sensitive to stressors, such as freeze-drying and high temperatures,” the study says indeed. The use of the coating, however, proves effective. Indeed, experiments show that the net protects the bacterium “from freeze-drying, high temperatures (50 oC), and high humidity.”

The coatings, in other words, prove extremely useful “against environmental stressors and represent a critical step towards enabling the production and storage of delicate microbes under nonideal conditions.” The composition of the nets, moreover, “is found to significantly impact its protective efficacy, and with optimized compositions, no viability loss is observed for MPN-coated microbes under conditions where uncoated cells do not survive.” Finally, the study shows that such protected microbes “improve germination of seeds by 150% as compared to those treated with fresh P. chlororaphis.”

Reducing the use of chemical fertilizers

Ariel Furst, the statement explains, has founded a company called Seia Bio to commercialize coated bacteria and use them on a large scale in regenerative agriculture. The hope is that the low cost of the manufacturing process will help make microbial fertilizers accessible to small farmers.

The ability to effectively replace chemical fertilizers is obviously the most relevant aspect. Conventional products, in fact, are made with an energy-intensive process and are characterized by an high climate impact. To the point of being a serious obstacle to achieving climate neutrality. Their long-term use also contributes to the gradual depletion of nutrient availability in the soil. A problem that can be remedied by using regenerative agriculture practices to restore the soil.