Two fungi, wich produced an acid and an alkaline-stable xylanase, were isolated from soil and identified as strains of Aspergillus niger. The basic characteristics of both xylanases were studied and the conditions of pretreating wheat straw pulps with xylanases were also optimized. The results showed that enzyme-pretreated pulps can obtain higher brightness, or 20%-30% of hypochlorine can be reduced at the same final brightness level. It can be predicted that xylanase has a great potential economic and environmental benefits in non-wood pulp bleaching in the near future.

The cellobiohydrolase II gene, cbh2 was amplified by polymerasechain reaction(PCR) from an enhanced cellulase-producing strain, Trichoderma k?ningii K, and then was cloned to T-easy vector. Sequence comparisons show that cbh2 of T. k?ningii is identical to that of T. reesei with the exception of 2 bp in the coding region, which cause an amino acid substituted in the mature CBHII protein. The similarity values between CBHII gene of T. k?ningii and reported cbh2 gene of Trichoderma reesei is 99.89%. The cbh2 gene of T. k?ningii is 1611bp long, and the coding region is interrupted by three short introns. The derived CBHII protein sequence is 471 amino acids long and three putative N-glycosylation sites is found.

Zymograms of the cultural supernatant of Aspergillus niger 149 showed xylanase^s two bands tentatively named X-I and X-II. X-I and X-II were purified to PAGE homogenity by (NH_(4))_(2)SO_(4) fractionation and DEAE-Sephadex A50 column chromatography. The molecular mass of X-I and X-II estimated by SDS-PAGE and concentration gradient PAGE and 37kDa, 76kDa, 24kDa and 23kDa, respectively. X-I and X-II contained 27.6% and 7.3% carbohybrate residues, respectively.