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A novel biocompatible magnetic cellulose nanocrystal (MCNC) composite was in situ prepared via a simple co-precipitation-electrostatic-self-assembly technique and was structurally characterized. The results showed that the anionic cellulose nanocrystals (CNCs) were successfully composited with cationic chitosan-coated Fe[sub 3]O[sub 4] by self-assembly technology. The electrostatic interaction between CNCs and chitosan, and that between chitosan and Fe[sub 3]O[sub 4], were the key driving forces for the formation of the composite. Papain, a widely used protease, could be successfully immobilized on the activated MCNCs with formaldehyde. The immobilized papain exhibited higher thermal stability than the free enzyme, with the relative activity being higher than 80% after incubation at 40 °C for 7 h while that of free papain was less than 30%. Also, the pH stability of immobilized papain was superior to that of free papain. Moreover, the immobilized papain showed significantly better tolerance to the three solvents tested compared with its free counterpart. The optimum range of pH for immobilized papain (pH 5-10) was remarkably wider than that of free enzyme (pH 5-7). The relative activities of immobilized papain at 50-70 °C were more than 90%, which significantly surpassed those of free papain. The immobilized papain also manifested excellent storage stability, with relative activity being as high as 93.6% after 16 days of storage at 4 °C Furthermore, the obtained kinetic constant values showed that papain immobilized on the MCNCs had relatively high catalytic efficiency. Additionally, the immobilized papain could be easily separated and recycled from the reaction system through magnetic forces. Obviously, the prepared MCNCs as novel supports are promising and competitive for enzyme immobilization. [ABSTRACT FROM AUTHOR]

The biocatalytic anti-Prelog enantioselective reduction of 4′-methoxyacetophenone (MOAP) to (R)-1-(4-methoxyphenyl)ethanol {(R)-MOPE} using immobilized Trigonopsis variabilisAS2.1611 cells was, for the first time, successfully conducted in an ionic liquid (IL)-containing system. Of all the tested ILs, the best results were observed in the co-solvent system containing 1-(2′-hydroxyl)ethyl-3-methylimidazolium nitrate (C2OHMIM·NO3), which showed the good biocompatibility with the cells and only a moderate increase in the cell membrane permeability. It was found that the optimal content of C2OHMIM·NO3, buffer pH, reaction temperature, substrate concentration and shaking rate were 2.5% (v/v), 8.5, 30 °C, 15 mM and 200 r min−1, respectively. Under these optimized conditions, the initial reaction rate, the maximum yield and the product e.e. were 7.1 μmol h−1, 97.2% and >99%, respectively, which are much higher than the corresponding values previously reported. The presence of C2OHMIM·NO3in aqueous buffer allowed the cells to tolerate relatively high temperatures and substrate concentrations compared with those in aqueous buffer without IL. Additionally, the immobilized cells manifested excellent operational and storage stability. Hence, the whole-cell biocatalytic anti-Prelog reduction of MOAP to (R)-MOPE on a preparative scale in the presence of C2OHMIM·NO3appears to be a promising and competitive reaction [ABSTRACT FROM AUTHOR]

Novel solid acid catalysts for esterification have recently been described that are made by incomplete carbonization of carbohydrates followed by sulfonation. Herein, such a ‘sugar catalyst’ is prepared from d-glucose and its catalytic properties and structure are investigated in detail. This type of sugar catalyst is, for the first time, applied for the effective production of biodiesel from waste oils. Our results indicate that sugar catalysts are highly effective, minimally polluting and re-usable catalysts that are highly suited to the production of biodiesel from waste oils with a high acid value. [ABSTRACT FROM AUTHOR]