|Aspergillus carbonarius. Source: JGI MycoCosm. Click to enlarge.|
Researchers at Washington State University have engineered the filamentous fungus Aspergillus carbonarius ITEM 5010 to produce jet-range hydrocarbons directly from biomass. The researchers hope the work, reported in the journal Fungal Biology, leads to economically viable production of aviation biofuels in the next five years.
The team led by Birgitte Ahring, director and Battelle distinguished professor of the Bioproducts, Sciences and Engineering Laboratory at WSU Tri-cities, found that the production of hydrocarbons was dependent on the type of media used. Therefore, they tested ten different carbon sources (oatmeal, wheat bran, glucose, carboxymethyl cellulose, avicel, xylan, corn stover, switch grass, pretreated corn stover, and pretreated switch grass) to identify the maximum number and quantity of hydrocarbons produced.
Among the hydrocarbons produced were undecane (C11H24), dodecane (C12H26), tetradecane (C14H30), hexadecane (C16H34) 2,4-dimethylhexane (C8H18), 4-methylheptane (C8H18), 3-methyl-1-butanol (C5H12O), ethyl benzene (C8H10), and o-xylene (C8H10).
The fungus produced the most hydrocarbons on a diet of oatmeal but also created them by eating wheat straw or the non-edible leftovers from corn production.
Fungi have been of interest for about a decade within biofuels production as the key producer of enzymes necessary for converting biomass to sugars. Some researchers further showed that fungi could create hydrocarbons, but the research was limited to a specific fungus living within a specific tree in the rainforest, and the actual hydrocarbon concentrations were not reported.
Ahring’s group has previously been successful in using standard Aspergillus fungi to produce enzymes and other useful products, which have been patented and are under commercialization, so they decided to look into A. carbonarius ITEM 5010’s potential for biofuels.
A. carbonarius produces the mycotoxin ochratoxin A (OTA, C20H18ClNO6)—one of the most-abundant food-contaminating mycotoxins. The production of OTA by Aspergillus carbonarius may be a main cause of the contamination of grape products. OTA is a known nephrotoxic, immunotoxic, and carcinogenic mycotoxin long been studied for its role in animal and human disease. OTA is a proven carcinogen in animals and is classified as a class 2B, possible human carcinogen by the International Agency for Research on Cancer. Toxicity from ochratoxin is considered serious enough that it is among approximately 20 mycotoxins monitored in food.
Fungi are complex microorganisms and are not always easy to work with, Ahring said. They have a complex biology that is often poorly understood. Ahring suspects the fungi produce hydrocarbons, large compounds that are costly for the organism to produce, as a protective mechanism. Her group showed that fungi react to bacterial attacks by increasing their hydrocarbon production.
The researchers were assisted by Kenneth Bruno, a researcher at the US Department of Energy’s Pacific Northwest National Laboratory, who developed a method essential for the genetic manipulation of A. carbonarius. The research received funding from the Danish Council for Strategic Research under the program for Energy and Environment.
Using fungi for hydrocarbon and biofuels production offers a benefit in that fungi can do the work themselves, bypassing multiple complicated chemical processes required by other biofuel production methods. Fungi also have great potential to create the fuel at low cost, Ahring said.
The researchers are now working to optimize the fungi’s hydrocarbon production and improve biochemical pathways through genetic engineering. They have obtained mutants with a higher production level and are working on improving these strains by using gene coding for specific hydrocarbons out of blue green bacteria and algae.
It’s the same challenge faced by mold researchers, more than a generation ago, who found they could only produce a tiny amount of their product, Ahring said. Eventually, they optimized production of their product—antibiotics.
Malavika Sinha, Annette Sørensen, Aftab Ahamed, Birgitte Kiær Ahring (2015) “Production of hydrocarbons by Aspergillus carbonarius ITEM 5010,” Fungal Biology, Volume 119, Issue 4, Pages 274-282 doi: 10.1016/j.funbio.2015.01.001