Enzymatic synthesis of aroma compound xylosides using transfer reaction by Trichoderma longibrachiatum xylanase

Enzymatic synthesis of aroma compound xylosides was performed by Trichoderma longibrachiatum xylanase. Information concerning the nature of xylosides present in the reaction medium was obtained by GC El MS, by GC-NCI-MS of TFA derivatives, and by positive FAB MS of the reaction mixtures. Moreover the structures of isolated benzyl beta D xylopyranoside and 4-O-beta xylopyranosyl beta D xylopyranoside were established by H-1 and C-13 NMR and heteronuclear two dimensional (H-1-C-13) chemical shift correlation. The results obtained for hexyl and benzyl alcohol xylosides indicated that a reaction implying a transfer of one to two or three xylose units from xylan was involved. The enzyme was able to recognize xylobiose xylotriose, and xylan as xylose donors. Benzyl xyloside produced independently of xylobioside and xylotrioside, was found as the major kinetic product of the reaction. Benzyl xyloside was produced in higher quantities and at a higher rate than that obtained for the di- and trixyloside derivatives. The maximum production for benzyl xyloside, 1 29 g/L, was obtained in the presence of hexane (50%) used as cosolvent. Xylosides and xylobiosides of several aroma compounds (Z)-hex 3 en 1 ol, heptan 2 ol, geraniol, nerol, and citronellol were synthesized in different amounts from 850 mg/L for (Z) hex 3 en 1 yl xylosides to 1.5 mg/L for citronellyl xylosides. No synthesis occurred when menthol, linalool and eugenol were used as acceptors.