Improving the energy balance of bioethanol production from winter cereals: the effect of crop production intensity

Energy balances were calculated on the basis of biennial field trials conducted at two locations in southwest Germany. Winter cereals (rye cultivar [`]Farino', triticale cv. [`]Modus', wheat cv. [`]Batis') were grown under different crop production conditions (and intensities) optimized for ethanol production. To minimize the use of fossil energy, previous legume crops (pea, grass-clover) or stillage were substituted for mineral nitrogen. Stillage is a liquid processing residue from bioethanol processing that contains nitrogen in organic form. Along with the grain, straw, and bioethanol yields per hectare, both the cultivation and conversion processes were considered. The net energy gains (GJ ha-1) and output/input ratios were computed either with or without by-product stillage and straw. As crop production intensity increased, both the energy output and the net energy gain per ha rose. However, the output/input ratios fell. Peak net energy gains (max. 56.4 GJ ha-1) and highest output/input ratios (max. 3.07) without by-product consideration occurred after a previous pea crop. In stillage manuring, the net energy gains remained minor in comparison to mineral nitrogen fertilization because of poor cereal yield. Hence, the entire replacement of mineral nitrogen with stillage could not be approved unreservedly. Replacing basic nutrients (i.e. P2O5, K2O) appears more feasible instead.Ethanol grain production Nitrogen substitution Grain-to-ethanol process Energy balance Net energy gain

Coenzyme binding in F-420-dependent secondary alcohol dehydrogenase, a member of the bacterial luciferase family

AbstractF420-dependent secondary alcohol dehydrogenase (Adf) from methanogenic archaea is a member of the growing bacterial luciferase family which are all TIM barrel enzymes, most of which with an unusual nonprolyl cis peptide bond. We report here on the crystal structure of Adf from Methanoculleus thermophilicus at 1.8 Å resolution in complex with a F420-acetone adduct. The knowledge of the F420 binding mode in Adf provides the molecular basis for modeling F420 and FMN into the other enzymes of the family. A nonprolyl cis peptide bond was identified as an essential part of a bulge that serves as backstop at the Re-face of F420 to keep it in a bent conformation. The acetone moiety of the F420-acetone adduct is positioned at the Si-face of F420 deeply buried inside the protein. Isopropanol can be reliably modeled and a hydrogen transfer mechanism postulated. His39 and Glu108 can be identified as key players for binding of the acetone or isopropanol oxygens and for catalysis