Sunday, May 3, 2009
6-16
Microbial contamination of Biodiesel
Marlin D. Vangsness, Loryn L. Bowen, Lisa M. Brown, Susan S. Mueller, and Lori M. Balster. Energy and Environmental Engineering, University of Dayton Research Institute, 300 College Park, Dayton, OH 45469
Biodiesel is a domestically produced, renewable fuel that can be manufactured from vegetable oils, animal fats, or even recycled restaurant greases. B-20 is more specifically a blend of 20% B-100 and 80% diesel and can be used in diesel engines without modification. Biodiesel tends to contain more polar species than petroleum based diesel. This results in a higher dissolved water content leading to more free water for microbial community growth. Microbial growth results in biofilm formation, increased corrosion of fuel system components as well as a reduction in the quality of the fuel. In order to control this growth it is important to understand how the consortium evolves in the fuel/water environment. A year-long study of the microbial contamination found in a single sample of B-20 was conducted using microbiological and molecular techniques. Over a period of one year, the biodiesel sample was recultured and PCR testing was redone to observe consortia changes at five different time points. Initially, growth was prolific on several types of media and several fungal and bacterial species were identified. Fungi were the dominant species during the early tests but bacterial species became the more dominant organisms as time progressed. By the 6 month time point, growth on culture medium had been reduced significantly with no fungi present and only a few bacterial species growing, which were predominately Gram positive cocci. Organisms found in the B-20 sample included Pseudomonas, Burkholderia, Methylobacterium, Sphingomonas, Ralstonia, Citrobacter, Agromyces, Hyphozyma, and Geotrichum.