April 06, 2015

Oil-producing fungus has antibacterial potential

Dairy Calves

By Jan Suszkiw, ARS Public Affairs Specialist

An oil produced by a naturally occurring fungus is being investigated by Agricultural Research Service (ARS) scientists as a potential antibiotic alternative for treating certain bacterial infections in livestock animals.

In Petri-dish experiments, drops of the oil, called liamocin, stopped the growth of six of seven species of Streptococcus bacteria, including two that cause mastitis, an udder infection in cows that costs the U.S. dairy industry $2 billion annually in economic losses. The evaluations coincide with concern that overuse of antibiotics has led to resistance in some infectious bacteria, undermining the drugs’ effectiveness in both veterinary and human medicine.

The yeast-like fungus Aureobasidium pullulans produces liamocin when grown in liquid culture. Of the 20 A. pullulans strains known to produce the oil, strain NRRL 50380 is perhaps the best described, notes microbiologist Kenneth Bischoff, with ARS’s National Center for Agricultural Utilization Research in Peoria, Illinois. However, the antibacterial properties of this strain’s oil had not previously been examined, Bischoff added.

Toward that objective, he and colleagues used liquid-culture fermentation techniques to grow the fungus so that sufficient amounts of its liamocin could be extracted and purified. The team then used high-pressure liquid chromatography to isolate the oil’s various chemical components. One compound,  liamocin B1, showed the highest level of antimicrobial activity against Streptococcus. In one test, for example, an hour’s exposure to 20 or 39 micrograms of the oil destroyed 50 and 88 percent, respectively, of S. agalactiae cells.

Other bacteria the team tested—including Staphylococcus aureus, Lactobacillus fermentum, Escherichia coli, and Pseudomonas aeruginosa—were unaffected by the oil when tested in Petri dish assays.

According to Bischoff, liamocin’s specificity could make it potentially useful in treating Streptococcus infections in cows, pigs and other livestock without jeopardizing beneficial bacteria that inhabit the animals. His investigation of the oil-producing fungus is part of a broader effort at the ARS center to create value-added products, including biofuels, from microorganisms and agricultural commodities.

A paper reporting the liamocin findings will appear in an upcoming 2015 issue of The Journal of Antibiotics.

ARS is the principal intramural scientific research agency of the U.S. Department of Agriculture.

SCIENTIFIC CONTACT: Kenneth Bischoff, ARS Renewable Product Technology Research Unit, National Center for Agricultural Utilization Research, 1815 North University St., Peoria, Illinois 61604; (309) 681-6067; kenneth.bischoff@ars.usda.gov.