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Kazembe-Phiri H.,Hiroshima University | Matsumura Y.,Hiroshima University | Minowa T.,Biomass Technology Research Center | Fujimoto S.,Biomass Technology Research Center
Nihon Enerugi Gakkaishi/Journal of the Japan Institute of Energy | Year: 2010

The effectiveness of bio-oils' heterogeneously-catalyzed ethanolysis, using groundnut (Arachis hypogaea) crude oil, activated calcium oxide (h-CaO), and surface-modified activated calcium oxide (s-CaO) for biodiesel production in developing countries, was studied in comparison with potassium hydroxide (KOH) and calcium hydroxide [Ca(OH)2] in terms of reaction, effect of catalyst type and loading of 1.0 wt%, molar ratio of 9:1, time ranging from 0.5 to 3.0 h, at 78°C and stirring speed of 1000 rpm. Ca(OH)2 was inferior to KOH, h-CaO and s-CaO regardless of reaction time, achieving fatty acid ethyl esters (FAEE) yields, after 0.5, 2, and 3 h, of 0.24 ± 0.03 wt%, 1.09 ± 0.72 wt%, 8.08 ± 0.80 wt% comparing 56.19 ± 1.98 wt%, 76.57 ± 2.20 wt%, 76.99 ± 4.18 wt% , and 62.32 ± 1.95 wt%, 88.81 ± 0.82 wt%, 85.30 ± 4.56 wt%, and 51.40 ± 1.76 wt%, 81.21 ± 1.30 wt%, 83.23 ± 1.09 wt%, respectively. The activity of h-CaO, s-CaO and KOH agreed quite well showing the comparable effectiveness of the catalysts on ethanolysis. Generally, yields decreased after 2-h, due to product adsorption after 2 h. We based on these results and concluded that this paper is the first to report the effectiveness of h-CaO and s-CaO for bio-oil heterogeneously catalyzed ethanolysis for sustainable biodiesel production in developing countries. Source

Kim H.-W.,Japan National Institute of Advanced Industrial Science and Technology | Kim H.-W.,Biomass Technology Research Center | Ishikawa K.,Japan National Institute of Advanced Industrial Science and Technology | Ishikawa K.,Biomass Technology Research Center
Biochemical Journal | Year: 2011

A hyperthermophilic membrane-related β-1,4-endoglucanase (family 5, cellulase) of the archaeon Pyrococcus horikoshii was found to be capable of hydrolysing cellulose at high temperatures. The hyperthermophilic cellulase has promise for applications in biomass utilization. To clarify its detailed function, we determined the crystal structures of mutants of the enzyme in complex with either the substrate or product ligands. We were able to resolve different kinds of complex structures at 1.65-2.01 Å (1 Å = 0.1 nm). The structural analysis of various mutant enzymes yielded a sequence of crystallographic snapshots, which could be used to explain the catalytic process of the enzyme. The substrate position is fixed by the alignment of one cellobiose unit between the two aromatic amino acid residues at subsites +1 and +2. During the enzyme reaction, the glucose structure of cellulose substrates is distorted at subsite -1, and the β-1,4-glucoside bond between glucose moieties is twisted between subsites -1 and +1. Subsite -2 specifically recognizes the glucose residue, but recognition by subsites +1 and +2 is loose during the enzyme reaction. This type of recognition is important for creation of the distorted boat form of the substrate at subsite -1. A rare enzyme - substrate complex was observed within the low-activity mutant Y299F, which suggested the existence of a trapped ligand structure before the formation by covalent bonding of the proposed intermediate structure. Analysis of the enzyme-substrate structure suggested that an incoming water molecule, essential for hydrolysis during the retention process, might be introduced to the cleavage position after the cellobiose product at subsites +1 and +2 was released from the active site. © The Authors Journal compilation © 2011 Biochemical Society. Source

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