MIT researches have examined gaseous substrates that could be made available at low cost and sufficiently large scale for industrial fuel production. To make it feasible they introduced a new bioconversion scheme that effectively converts syngas, generated from gasification of coal, natural gas, or biomass, into lipids that can be used for biodiesel production.
The strategy used is an integrated conversion method comprising a two-stage integrated bioprocess:
In the first stage, an anaerobic bioreactor converts mixtures of gases of CO2 and CO or H2 to acetic acid, using the anaerobic acetogen Moorella thermoacetica.
The acetic acid product is fed as a substrate to a second bioreactor, where it is converted aerobically into lipids by an engineered oleaginous yeast, Yarrowia lipolytica.
Additionally, as the rate of CO2 fixation substantially exceeds that of CO2 generation in the two units of the process, there is significant potential for CO2 recycling in this integrated system. In a broader sense, implementation of these concepts for fuel production may extend to a number of commercially important biological platforms, depending on the potential sources of synthesis gas or its conversion products, namely, acetate.
See it in PNAS.