Monday, May 2, 2011
Grand Ballroom C-D, 2nd fl (Sheraton Seattle)
Microalgae have attracted considerable global attention at present due to their capabilities in producing renewable transportation fuels, bioremediating industrial water pollution, and reducing the greenhouse gas emissions. Unfortunately, a major bottleneck to algae-based fuels is the high cost when competitive with conventional fossil fuels. Biomethane production via anaerobic digestion has been regarded as a practical approach to disposing and utilizing the spent algal biomass. However, the high protein content (30-60%) in algal biomass could produce high levels of total ammonia nitrogen (TAN) that strongly inhibits methanogenesis. Moreover, the high concentration of TAN could result in the production of high concentrations of accumulated carboxylic acids. These carboxylic acids could be effective feedstock for downstream production of important commodity and specialized chemicals. Furthermore, the TAN from algal protein could neutralize the carboxylic acids as a result of reducing supplement of ammonium bicarbonate buffer, which is superior to calcium carbonate in the fermentation of carboxylic acids as described by Fu and Holtzapple (2010). Therefore, it is more attractive to transform algal debris biomass to carboxylates by rumen microorganisms. Our preliminary data shows that the concentrations of total carboxylic acid can reach 36.0 g/l in the anaerobic digester. To our knowledge, this presentation firstly describes the essential information required for the conversion of algal biomass to carboxylates, including the optimal conditions to maximize the total carboxylate salts yield, the carboxylate salts productivity, and net energy production as well as the structure and dynamics of the microbial communities involved in the carboxylates platform for biofuel.