Monday, April 29, 2013
Exhibit Hall
At the University of Bath, the yeast Metschnikowia pulcherrima, has been evaluated for its potential to produce biofuels from waste streams. M. pulcherrima has been used previously as a biofungicide in post-harvest disease control, however, we have discovered that M. pulcherrima can accumulate 45% dry weight in lipid under favourable conditions. Significantly, M. pulcherrima is both mesophilic and acidophilic, with optimum growth rates at 17-25 °C and pH 3.5-5. The yeast also secretes antimicrobial compounds, such as pulcherriminic acid and 2-phenylethanol, into the culture medium. These attributes make M. pulcherrima an extremely promising source of inexpensive lipids for biofuel manufacture, since the combination of antimicrobials, low pH and temperature dramatically reduce the likelihood of invasion from non-productive species allowing large scale culture in cheap vessels or in open ponds with little or no protection from invasion. Both scenarios would reduce the cost of production substantially. M. pulcherrima has been grown in non-sterile conditions on an ammonium and nitrate rich wastewater, and on a range of sugars and oligosaccharides.
However, the oils produced by these yeasts, while similar to vegetable oils, also contain high levels of sterols. Although the triglyceride portion of the oils can be esterified into biodiesel, the sterols are solids at room temperature. Two further methods have been assessed to chemically upgrade the sterol rich oil to produce a promising 3rd generation biofuel. The first is a transesterification reaction with short chain esters, while the second uses zeolite catalysts to produce a hydrocarbon fuel.