Montana State researchers uncover unique lipid-producing fungus
A research project at Montana State University has discovered a fungus that can eat algae and effectively ooze oil when dried. “The innovative process we have developed utilizes a novel acidophilic fungi (referred to as strain MK7) obtained from Yellowstone National Park (YNP) to directly convert lignocellulosic feedstock, five- and six-carbon sugars, and algae biomass to lipids for biodiesel using a remarkable minimal number of steps,” said Mark Kozubal, a post doctoral research associate at MSU.
According to Kozubal, he discovered the fungus strain through his studies in extreme Archaea in YSP hot springs that live in low-pH, high-temperature environments. “As these springs cool I noted that they feed into an algae-rich biomass portion of the spring at about 35 degrees Celsius,” he said. “Within this algae I noticed fungi living on or with the algae. The pH of this biofilm was about 2.5-3.0. I decided to try to algae in the lab, but always ended up with the fungi, which was very interesting because nobody studies fungi in YNP springs. Virtually no studies have been done. I had read somewhere that fungi could accumulate a lot of lipids, so I tested strain MK7 on some feedstock and realized that it indeed did make a lot.” In fact, lipids accounted for up to 60 percent of the cell volume of the fungi. “I also realized that it was growing quite well on all sorts of feedstocks, [including] wheat straw, hardwood, yard wastes, olive oil and sugars,” Kozybal continued. “That’s when we decided to pursue the organism.”
There are several ways in which the fungus is unique. First, Kozubal noted that MK7 can grow at a pH range of 0.7-7.0, which is quite a bit lower than related strains. “We suspect the enzymes to be more active at this low pH, which would be valuable for the conversion of lignocelluloses to sugars,” he continued. MK7 is also capable of directly converting lignocellulosic feedstock into energy-rich metabolites with few pretreatment steps and no enzymes, which makes the process relatively simple and inexpensive. In addition, the strain can produce lipids from these feedstocks over a wide pH range, which negates the cost pH neutralization steps. According to Kozubal, MK7 produces a more favorable lipid profile for biofuels, biolubricants and other applications when compared to algae and other lipid-producing organisms. Another benefit is the strain is highly resistant to contamination by other organisms. Furthermore, MK7 has a high tolerance to manganese, which is used to increase the rate of lignin degradation. It also has a high tolerance to metals and low pH, allowing it to be incorporated into remediation strategies. Kozubal also points out that related strains of fungi have been shown to be easy targets for genetic manipulation.
Additional benefits of MK7 include the fact that the entire process of lipid production can be done in a single vessel, which Kozubal said will enhance cost effectiveness. While dewatering has been an issue with algae production, Kozubal noted that MK7 is easily removed from liquid phase, and therefore easy to dry for lipid extraction protocols. The process to extract oil might also be easier. “Algal cell walls are quite hard to extract from,” Kozubal said. “This organism seems less difficult, but much needs to be studied.”
According to Kozubal, 1 ton of wheat straw has been converted into about 160 pounds of lipid during his research project. That equates to about 22 gallons of biodiesel. “This is much better than the very few studies that have been done to use fungi for direct conversion” via a consolidated bioprocessing technology, he said. The next step in MK7 research will be to find additional funding sources. Kozubal also said his group would love to have the support of an industry partner.