Bioenergy Systems Research Institute, The University of Georgia

来源: 时间:June 13, 2014, 1:14 a.m.

The Bioenergy Systems Research Institute encourages and facilitates: (a) integrative, collaborative basic and applied research projects in bioenergy that recognize the entire lifecycle and environmental impact of biomass production, harvesting, transport, treatment, conversion, and recycling; (b) education and training of the next generation of scientists and engineers that will form the 21st century workforce in the alternative energy field; (c) outreach and communication activities to involve our public and private stakeholders in the development and dissemination of next-generation bioenergy technologies.

Exploiting microbial hyperthermophilicity to produce an industrial chemical, using hydrogen and carbon dioxide

Microorganisms can be engineered to produce useful products, including chemicals and fuels from sugars derived from renewable feedstocks, such as plant biomass. An alternative method is to use low potential reducing power from nonbiomass sources, such as hydrogen gas or electricity, to reduce carbon dioxide directly into products. This approach circumvents the overall low efficiency of photosynthesis and the production of sugar intermediates. Although significant advances have been made in manipulating microorganisms to produce useful products from organic substrates, engineering them to use carbon dioxide and hydrogen gas has not been reported. Herein, we describe a unique temperature-dependent approach that confers on a microorganism (the archaeon Pyrococcus furiosus, which grows optimally on carbohydrates at 100°C) the capacity to use carbon dioxide, a reaction that it does not accomplish naturally. This was achieved by the heterologous expression of five genes of the carbon fixation cycle of the archaeonMetallosphaera sedula, which grows autotrophically at 73°C. The engineered P. furiosus strain is able to use hydrogen gas and incorporate carbon dioxide into 3-hydroxypropionic acid, one of the top 12 industrial chemical building blocks. The reaction can be accomplished by cell-free extracts and by whole cells of the recombinant P. furiosus strain. Moreover, it is carried out some 30°C below the optimal growth temperature of the organism in conditions that support only minimal growth but maintain sufficient metabolic activity to sustain the production of 3-hydroxypropionate. The approach described here can be expanded to produce important organic chemicals, all through biological activation of carbon dioxide.

Today, almost all ethanol—at least in the United States—comes from converting corn kernels into fuel. But because farming corn requires lots of energy and fertilizer, corn ethanol doesn't actually do much to reduce petroleum use or greenhouse gas emissions. Several companies are working to convert agricultural waste—known as cellulosic biomass—into ethanol. But they've had a hard time making it as cheaply as corn ethanol, because it's costly to break down biomass into sugars that microbes can ferment. Now, researchers in the United States have engineered a microbe that both breaks down cellulose into sugar and ferments it to produce ethanol.

Researchers from the University of Georgia and at Tennessee’s Oak Ridge National Laboratory have engineered the thermophilic bacteriumCaldicellulosiruptor bescii to directly convert switchgrass into ethanol, according to a study published today (June 2) in PNAS

Direct conversion of plant biomass to ethanol by engineeredCaldicellulosiruptor bescii

The ever-increasing demand for transportation fuels, the decrease in global petroleum reserves, and the negative impact of greenhouse gases resulting from burning petroleum make renewable and sustainable biofuels an imperative for the future. First-generation biofuels produced from food crops are limited by cost and competition with food supply. Considerable effort has been made to produce fuels from lignocellulosic biomass, but the need for chemical and enzymatic pretreatment to solubilize the biomass prior to microbial bioconversion is a major economic barrier to the development of an industrial process. Here we report the metabolic engineering of a bacterium, Caldicellulosiruptor bescii, that is capable of using unprocessed switchgrass, an abundant, environmentally desirable, and economically sustainable lignocellulosic plant biomass, as feedstock to produce ethanol.

Engineered Microbe Could Ease Switch to Grass

Researchers modify a heat-loving bacterium so it can produce biofuel from switchgrass directly, with no need for costly chemical and enzymatic treatments.