Could “armored” bacteria replace chemical fertilizers?

Conventional chemical fertilizers aren’t among the most eco-friendly substances in the world, which is one reason why some farmers are exploring the use of beneficial bacteria as an alternative. A new coating technology could make such microbes more widely available than ever before.

Not only do traditional chemical fertilizers pollute the environment if they get into waterways, they also deplete nutrients in the soil over time. What’s more, they’re relatively expensive.

Seeking a greener and more sustainable alternative, some farmers have started applying nitrogen-fixing bacteria to their crops. These microbes absorb nitrogen gas from the atmosphere and convert it into ammonia in the soil. That ammonia provides the plants with nutrients, restores depleted soil, and boosts the plants’ natural defenses against pest insects.

One problem with the bacteria, however, is the fact that they are very sensitive to excessive heat and humidity. This means they don’t stand up well to being shipped out to farms from a central source. It’s possible to grow them at farms in large fermenters, although building and maintaining those fermenters can be quite expensive.

With these drawbacks in mind, Asst. Prof. Ariel Furst and colleagues at MIT have created a method of coating the microbes in tiny “metal-phenol network” (MPN) shells. Although these coatings don’t hinder the bacteria’s growth or functions, they do provide protection from heat and humidity. The coated bacteria can even be freeze-dried, then shipped and applied to crops as a powder.

Furst’s team created 12 different MPNs which incorporated metals such as iron, manganese, aluminum and zinc, all of which are considered safe for use as food additives. The shells also contained organic compounds called phenols, which are “generally regarded as safe” by the FDA.

When these MPNs were used on nitrogen-fixing Pseudomonas chlororaphis bacteria, all 12 of them were found to protect the microbes from temperatures of up to 50 ºC (122 ºF) and from relative humidity of up to 48%.

The most effective of the MPNs consisted of a combination of manganese and a polyphenol known as epigallocatechin gallate. P. chlororaphis coated in that shell were heated to 50 ºC, then placed in a lab dish along with seeds of crop plants such as dill, corn, radishes and bok choy. In all cases, the germination rate of the seeds improved by 150% as compared to when fresh but uncoated bacteria were added.

Furst is now commercializing the technology through a spinoff company she founded, called Seia Bio.

“When we think about developing technology, we need to intentionally design it to be inexpensive and accessible, and that’s what this technology is,” she said. “It would help democratize regenerative agriculture.”

A paper on the research was recently published in the Journal of the American Chemical Society Au.

Source: MIT

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