Biobased industrial products: Back to the future for agriculture

The NRC report on biobased industrial products provides a roadmap for research and commercialization policy needed for agriculture to go back to the future and reclaim its higher-value industrial product markets. The market-pull and technology-push dynamics are poised for this, and the US desperately needs to reclaim control of its agricultural, chemical and energy economies as well as enhance overall environmental quality for the future

Characterization of pectinolytic enzymes of Clostridium thermosulfurogenes

Pectinolytic activity is of general importance to the degradation of organic matter in the biosphere and as a biochemical agent of plant spoilage or pathogenesis [1-4]. Certain types of pectinolytic enzymes are vendable and of significance to agricultural and food processing [1,2]. Enzymes from thermophilic bacteria often possess higher catalytic activity and stability than<br />those of mesophilic microorganisms [5]. Nonetheless, only recently has a polygalacturonate lyase (EC 4.2.2.10) been characterized from the caldoacrive bacterium, Bacillus stearothermophilus [6]. We recently isolated and described the properties of Clostridium thermosulfurogenes that was obtained from Yellowstone National Park, U.S.A. [7]. This species was novel because it transformed thiosulfate into elemental sulfur which accumulated in the medium and cells and because it proliferated with a doubling time of 2 h on glucose as well as pectin. However, the general enzymatic features of the pectinolytic activity displayed by this new species were not described. This communication shows that C. thermosulfurogenes produces an active thermostable polygalacturonate hydrolase (EC 3.2.1.15) and pectin methylesterase (EC 3.1.1.11)

Extracellular Iron Reduction Is Mediated in Part by Neutral Red and Hydrogenase in Escherichia coli

Both microbial iron reduction and microbial reduction of anodes in fuel cells can occur by way of soluble electron mediators. To test whether neutral red (NR) mediates iron reduction, as it does anode reduction, by Escherichia coli, ferrous iron levels were monitored in anaerobic cultures grown with amorphous iron oxide. Ferrous iron levels were 19.4 times higher in cultures fermenting pyruvate in the presence of NR than in the absence of NR. NR did not stimulate iron reduction in cultures respiring with nitrate. To explore the mechanism of NR-mediated iron reduction, cell extracts of E. coli were used. Cell extract-NADH-NR mixtures had an enzymatic iron reduction rate almost 15-fold higher than the chemical NR-mediated iron reduction rate observed in controls with no cell extract. Hydrogen was consumed during stationary phase (in which iron reduction was detectable) especially in cultures containing both NR and iron oxide. An E. coli hypE mutant, with no hydrogenase activity, was also impaired in NR-mediated iron reduction activity. NR-mediated iron reduction rates by cell extracts were 1.5 to 2 times higher with hydrogen or formate as the electron source than with NADH. Our findings suggest that hydrogenase donates electrons to NR for extracellular iron reduction. This process appears to be analogous to those of iron reduction by bacteria that use soluble electron mediators (e.g., humic acids and 2,6-anthraquinone disulfonate) and of anode reduction by bacteria using soluble mediators (e.g., NR and thionin) in microbial fuel cells

Insights into Actinobacillus succinogenes Fermentative Metabolism in a Chemically Defined Growth Medium

Chemically defined media allow for a variety of metabolic studies that are not possible with undefined media. A defined medium, AM3, was created to expand the experimental opportunities for investigating the fermentative metabolism of succinate-producing Actinobacillus succinogenes. AM3 is a phosphate-buffered medium containing vitamins, minerals, NH(4)Cl as the main nitrogen source, and glutamate, cysteine, and methionine as required amino acids. A. succinogenes growth trends and end product distributions in AM3 and rich medium fermentations were compared. The effects of NaHCO(3) concentration in AM3 on end product distribution, growth rate, and metabolic rates were also examined. The A. succinogenes growth rate was 1.3 to 1.4 times higher at an NaHCO(3) concentration of 25 mM than at any other NaHCO(3) concentration, likely because both energy-producing metabolic branches (i.e., the succinate-producing branch and the formate-, acetate-, and ethanol-producing branch) were functioning at relatively high rates in the presence of 25 mM bicarbonate. To improve the accuracy of the A. succinogenes metabolic map, the reasons for A. succinogenes glutamate auxotrophy were examined by enzyme assays and by testing the ability of glutamate precursors to support growth. Enzyme activities were detected for glutamate synthesis that required glutamine or α-ketoglutarate. The inability to synthesize α-ketoglutarate from glucose indicates that at least two tricarboxylic acid cycle-associated enzyme activities are absent in A. succinogenes