The steady increase of energy demand causes two concerns: depletion of fossil fuel reserves and emissions of polluting gases. Because of this, during the past few decades research has been strengthened to find more environmentally-friendly renewable alternatives, including biofuels.
Sara Ramió Pujol has focused her doctoral thesis on two biofuels that can be synthetized by bacteria: bioethanol and biobuthanol. The synthesis of bioalcohols through sugar fermentation has been known from antique times and started to be exploited commercially some decades ago. However, the core research work of this thesis lies on the ability of a group of bacteria to produce bioalcohols through more simple substrates: hydrogen (H2), carbon dioxide (CO2) and carbon monoxide (CO) – the latter two, greenhouse gases. Thus, we are dealing with a process that a priori could lead to the sustainable production of bioalcohol and at the same time reduce polluting emissions. Nevertheless, industrial scale-up still presents some difficulties: the mixture of gases should be oxygen free; very few bacteria are known that can grow under these conditions and produce alcohols; and, finally, those bacteria that fulfil these two requirements also produce acids and in larger amounts.
The availability of proper substrate is possible thanks to the gasification of urban and agricultural waste. Gasification is an industrial process to treat waste at high pressure and temperature and convert it into the so-called syngas – precisely, a mixture of CO2, CO and H2 free of oxygen. Concerning the acids produced in the biological fermentation, they can also be used as raw material in different chemical processes. However, a good knowledge of bacteria metabolism is needed to control their production and favour the synthesis of alcohols. Sara Ramió has achieved this goal through a set of experiments at lab scale, always using syngas.
Two of the most significant results of the thesis are the relevance that turned out to have the temperature at which bacteria grow and the state of the bacteria at the time of experiments beginning. Moreover, new knowledge has been gathered on bacteria metabolism that can be applied at industrial scale.
The thesis is entitled “Insights into key parameters for bio-alcohol production in syngas fermentation using model carboxydotrophic bacteria” and has been directed by Dr Jesús Colprim (LEQUIA research group), Dr Lluís Bañeras (geMM research group) and Dr Ramon Ganigué (currently member of CMET research group of University of Ghent in Belgium). The defence, which is open to the public, will take place on July 7th at 11:00h at UdG Faculty of Sciences (Aula Magna).
Photo: Clostridium carboxidivorans P7, one of the strains studied by Sara Ramió in her doctoral thesis.