Zymomonas to make ethanol biofuel using N2 gas as nitrogen nutrient source ?
As to a study published in PNAS that Zymomonas can fix nitrogen gas from the atmosphere, Jenny Rood writes in The Scientist
The results suggest that elemental nitrogen could one day replace the traditional industrially produced, expensive, and environmentally damaging ammonium added to biofuel reactors as the source of a nutrient that is necessary for the growth of microorganisms that break down plant cellulose into ethanol.
The summary of the Indiana University release notes:
Biologists believe they have found a faster, cheaper and cleaner way to increase bioethanol production by using nitrogen gas, the most abundant gas in Earth's atmosphere, in place of more costly industrial fertilizers. The discovery could save the industry millions of dollars and make cellulosic ethanol -- made from wood, grasses and inedible parts of plants -- more competitive with corn ethanol and gasoline.
The article in The Scientist also noted caution expressed by Jim McMillan of NREL as to high branching rate leading to overgrowth by other organisms:
“It’s an excellent approach, but it’s not a fait accompli by a long shot,” said James “Jim” McMillan of the National Renewable Energy Laboratory in Golden, Colorado. “How far it can go into commercial production remains to be seen.” One concern is the bacterium’s slow growth rate when it is both pumping out ethanol and fixing nitrogen. “While the low cell mass yield is good from the standpoint of maximizing the amount of carbon that can go to ethanol production, it makes Zymomonas more vulnerable to be outgrown by undesirable contaminating microbes,” McMillan added in an e-mail.
Citation for PNAS paper: N2 gas is an effective fertilizer for bioethanol production by Zymomonas mobilis. Timothy A. Kremer, Breah LaSarre, Amanda L. Posto, and James B. McKinlay. PNAS, February 2, 2015 DOI: 10.1073/pnas.1420663112
from US 20110177551:
 As the microorganisms or culture cells that can be used for producing succinic acid, microorganisms or culture cells to which an ethanol producing ability is artificially improved may be used.