001. Jordan Peccia, Berat Haznedaroglu, James Gutierrez, Julie B. Zimmerman. Department of Chemical and Environmental Engineering, Yale University, 9 Hillhouse Avenue, P.O. Box 208286, New Haven, CT, 06520, USA. Nitrogen supply is an important driver of sustainable microalgae biofuel production. Trends in Biotechnology, 2013, 31(3), Pages: 134-138.
Favorable growth characteristics continue to generate interest in using triacylglycerides (TAGs) produced from microalgae for biodiesel feedstocks. In this opinion article, we suggest that due to the energy consumption associated with the production of external nitrogen fertilizers, the manner in which nitrogen is supplied to microalgae biorefineries will be an important driver of energy yields, sustainability, and commercial success. Schemes including the re-use of urban wastewater represent improvements on the overall energy balance, but will not allow for significant production of biofuels unless the nitrogen from the non-TAG portions of microalgae is recycled. Approaches to recycling nitrogen require an improved understanding of the tradeoffs between the different potential uses of the non-TAG microalgal portion (i.e., energy production via anaerobic digestion or thermal catalytic processes), and the development of nitrogen separation technologies.
Keywords: microalgae biofuels; life cycle analysis; nitrogen recycle; cyanobacteria; nitrogen fixation; wastewater.
002. Je Hyeong Jung, Wilfred Vermerris, Maria Gallo, Jeffrey R. Fedenko, John E. Erickson, Fredy Altpeter. Agronomy Department, University of Florida, IFAS, Gainesville, FL, USA. RNA interference suppression of lignin biosynthesis increases fermentable sugar yields for biofuel production from field-grown sugarcane. Plant Biotechnology, 2013, 11, Pages: 709–716.
The agronomic performance, cell wall characteristics and enzymatic saccharification efficiency of transgenic sugarcane plants with modified lignin were evaluated under replicated field conditions. Caffeic acid O-methyltransferase (COMT) was stably suppressed by RNAi in the field, resulting in transcript reduction of 80%–91%. Along with COMT suppression, total lignin content was reduced by 6%–12% in different transgenic lines. Suppression of COMT also altered lignin composition by reducing syringyl units and p-coumarate incorporation into lignin. Reduction in total lignin by 6% improved saccharification efficiency by 19%–23% with no significant difference in biomass yield, plant height, stalk diameter, tiller number, total structural carbohydrates or brix value when compared with nontransgenic tissue culture–derived or transgenic control plants. Lignin reduction of 8%–12% compromised biomass yield, but increased saccharification efficiency by 28%–32% compared with control plants. Biomass from transgenic sugarcane lines that have 6%–12% less lignin requires approximately one-third of the hydrolysis time or 3- to 4-fold less enzyme to release an equal or greater amount of fermentable sugar than nontransgenic plants. Reducing the recalcitrance of lignocellulosic biomass to saccharification by modifying lignin biosynthesis is expected to greatly benefit the economic competitiveness of sugarcane as a biofuel feedstock.
Keywords: caffeic acid O-methyltransferase (COMT); field performance; lignocellulosic biofuel; saccharification efficiency; Saccharum; sugarcane.
|