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Genipin, a reagent of plant origin was used for the immobilization of lipase by cross-linking to chitosan beads. The catalytic properties and operational and storage stabilities of the immobilized lipase were compared with the soluble lipase. Under optimum conditions, 198 microg protein was bound per g chitosan with a protein-coupling yield of 35%. The hydrolytic activity was 10.8 U/g chitosan and the relative specific activity was 108%. The immobilized lipase showed better thermal and pH stabilities compared to the soluble form. The immobilized enzyme exhibited mass transfer limitations as reflected by a higher apparent K(m) value and a lower energy of activation. The immobilized enzyme retained about 74% of its initial activity after five hydrolytic cycles.

A surface anchoring motif using the ice nucleation protein (INP) of Xanthomonas campestris pv. campestris BCRC 12,846 for display of transglucosidase has been developed. The transglucosidase gene from Xanthomonas campestris pv. campestris BCRC 12,608 was fused to the truncated ina gene. This truncated INP consisting of N- and C-terminal domains (INPNC) was able to direct the expressed transglucosidase fusion protein to the cell surface of E. coli with apparent high enzymatic activity. The localization of the truncated INPNC-transglucosidase fusion protein was examined by Western blot analysis and immunofluorescence labeling, and by whole-cell enzyme activity in the glucosylation of hydroquinone. The glucosylation reaction was carried out at 40 degrees C for 1 h, which gave 23 g/L of alpha-arbutin, and the molar conversion based on the amount of hydroquinone reached 83%. The use of whole-cells of the wild type strain resulted in an alpha-arbutin concentration of 4 g/L and a molar conversion of 16% only under the same conditions. The results suggested that E. coli displaying transglucosidase using truncated INPNC as an anchoring motif can be employed as a whole-cell biocatalyst in glucosylation.