One-pot chemo-enzymatic conversion of D-xylose to furfuralcohol by sequential dehydration with oxalic acid plus tin-based solid acid and bioreduction with whole-cells.

In this study, organic acid could be used as co-catalyst for assisting solid acid SO42-/SnO2-argil to convert hemicellulose-derived D-xylose into furfural. The relationship between pKa of organic acid and turnover frequency (TOF) of co-catalysis with organic acid plus SO42-/SnO2-argil was explored on the conversion of D-xylose to furfural. Oxalic acid (pKa = 1.25) (0.35 wt%) was found to be the optimum co-catalyst for assisting SO42-/SnO2-argil (3.6 wt%) to synthesize furfural from D-xylose (20 g/L) at 180 °C for 20 min, and the furfural yield and TOF could be obtained at 57.07% and 6.26 h-1, respectively. Finally, the obtained furfural (107.6 mM) could be completely biotransformed to furfuralcohol by recombinant Escherichia coli CCZU-K14 whole-cells at 30 °C and pH 6.5 in the presence of 1.5 mol glucose/mol furfural and 400 mM D-xylose. Clearly, this strategy shows high potential application for the effective synthesis of furfuralcohol from biomass-derived D-xylose.

Effective Utilization of Carbohydrate in Corncob to Synthesize Furfuralcohol by Chemical-Enzymatic Catalysis in Toluene-Water Media.

In this study, carbohydrates (cellulose plus hemicellulose) in corncob were effectively converted furfuralcohol (FOL) via chemical-enzymatic catalysis in a one-pot manner. After corncob (2.5 g, dry weight) was pretreated with 0.5 wt% oxalic acid, the obtained corncob-derived xylose (19.8 g/L xylose) could be converted to furfural at 60.1% yield with solid acid catalyst SO42-/SnO2-attapulgite (3.6 wt% catalyst loading) in the water-toluene (3:1, v/v) at 170 °C for 20 min. Moreover, the oxalic acid-pretreated corncob residue (1.152 g, dry weight) was enzymatically hydrolyzed to 0.902 g glucose and 0.202 g arabinose. Using the corncob-derived glucose (1.0 mM glucose/mM furfural) as cosubstrate, the furfural liquor (48.3 mM furfural) was successfully biotransformed to FOL by recombinant Escherichia coli CCZU-A13 cells harboring an NADH-dependent reductase (SsCR) in the water-toluene (4:1, v/v) under the optimum conditions (50 mM PEG-6000, 0.2 mM Zn2+, 0.1 g wet cells/mL, 30 °C, pH 6.5). After the bioreduction for 2 h, FAL was completely converted to FOL. The FOL yield was obtained at 0.11 g FOL/g corncob. Clearly, this one-pot synthesis strategy shows high potential application for the effective synthesis of FOL.

Chemical-enzymatic conversion of corncob-derived xylose to furfuralcohol by the tandem catalysis with SO42-/SnO2-kaoline and E. coli CCZU-T15 cells in toluene-water media.

One-pot synthesis of furfuralcohol from corncob-derived xylose was attempted by the tandem catalysis with solid acid SO42-/SnO2-kaoline and recombination Escherichia coli CCZU-T15 whole-cells in the toluene-water media. Using SO42-/SnO2-kaoline (3.5wt%) as catalyst, the furfural yield of 74.3% was obtained from corncob-derived xylose in the toluene-water (1:2, v:v) containing 10mM OP-10 at 170°C for 30min. After furfural liquor was mixed with corncob-hydrolysate from the enzymatic hydrolysis of oxalic acid-pretreated corncob residue, furfural (50.5mM) could be completely biotransformed to furfuralcohol with Escherichia coli CCZU-T15 whole-cells harboring an NADH-dependent reductase (ClCR) in the toluene-water (1:3, v:v) containing 12.5mM OP-10 and 1.6mM glucose/mM furfural at 30°C and pH 6.5. Furfuralcohol was obtained at 13.0% yield based on starting material corncob (100% furfuralcohol yield for bioreduction of furfural step). Clearly, this one-pot synthesis of furfuralcohol strategy shows high potential application for the effective utilization of corncob.

High resolution electron momentum spectroscopy of dichlorodifluoromethane: unambiguous assignments of outer valence molecular orbitals.

On account of controversial orbital assignment that appeared in previous works, [J. Chem. Phys. 120, 7933 (2004), and references therein] high resolution electron momentum spectroscopy (EMS) measurements on dichlorodifluoromethane has been carried out using a newly developed high resolution energy-momentum dispersive multichannel spectrometer employing asymmetric noncoplanar geometry at an impact energy of 2500 eV plus binding energy. Four resolved structures and two shoulders were obviously observed in high resolution binding energy spectrum in energy range covering eight outermost valence orbitals, whereas only two broad lobes were resolved in previous EMS studies [J. Chem. Phys. 120, 7933 (2004); Chin. Phys. 14, 2467 (2005)]. The ordering of these orbitals was reassigned unambiguously by simple comparison of experimental momentum distributions with theoretical ones.