XYLANASE INDUCTION BY L-SORBOSE IN A FUNGUS, TRICHODERMA-REESEI PC-3-7

Xylanase induction by L-sorbose was studied in a resting cell system o f a filamentous fungus, Trichoderma reesei PC-3-7, a hypercellulolytic mutant, and compared with that by other inducers. L-Sorbose induced x ylanase activity as well as cellulase. It induced a higher level of xy lanase activity than sophorose and xylose did. Three main xylanases, x ylanase I (Xyn I), xylanase II (Xyn II), and a non-specific endoglucan ase I (EG I), were separated using cation-exchange chromatography, and their activity were measured. Xyn II was induced in about the same pr oportion (60-80% of the total xylanase activity) by all inducers used. On the other hand, Xyn I was apparently induced by L-sorbose, xylose, and xylooligosaccharides, but only a little by sophorose. Northern bl ot analysis showed that L-sorbose induced Xyn I and Xyn II at the tran scriptional level, and more xyn1 mRNA was transcribed after L-sorbose addition than after sophorose. These results suggested that the expres sions of both Xyn I and Xyn II are regulated, at least in part, in a d ifferent manner. Furthermore, the Xyn I induction by L-sorbose indicat ed that an unknown common regulatory mechanism may exist between Xyn I and cellulase inductions.