Studies on the catalytic performance of lignin peroxidase in nonionic reversed micelles / 生物工程学报

Lignin peroxidase (LiP) hosted in Brij 30/cyclohexane/water nonionic reversed micelle could express its catalytic activity, but in Triton X-100/n-pentanol/cyclohexane/water nonionic reversed micelle LiP didn't show any catalytic activity. Some key factors that affected the catalytic activity of LiP in Brij 30 reversed micelle were studied at 20 degrees C. The optimum conditions were:omega0 = 8.5, pH = 2.2, [Brij30] = 600 mmol/L; under these conditions the half time of LiP was ca. 50 hours. As compared with the properties of LiP in aqueous solution, the activity of LiP hosted in Brij 30 reversed micelle dropped, but its stability improved greatly. To reveal the role of normal alcohol, which was a necessary component for forming Triton X-100 reversed micelles, the effect of n-pentanol on the catalytic activity of LiP in Brij 30 reversed micelle was investigated. Results indicated that high concentration of the alcohol deactivated LiP. So it was deduced that the phenomenon that LiP hosted in the Triton X-100 reversed micelles could not express its activity was mainly due to the alcohol co-surfactant.

Effect of supercritical CO2 to cellulase reaction / 生物工程学报

The effects of pretreatment of supercritical carbon dioxide (SC-CO2) on the supramolecular structure of cellulose and the cellulase catalyzed reaction were investigated. The cellulase activity was not affected when it was treated with SC-CO2 at 10MPa and at 50 degrees C for 30 min. But when the cellulase was treated by SC-CO2 in the presence of cellulose, the catalytic activity of the cellulase was lost. The cellulose pretreated with or without cellulase under the same SC-CO2 condition was then hydrolyzed with tresh crude cellulase. The final reducing sugar yield from the hydrolysis of the cellulose pretreated with cellulase was higher than that of the cellulose pretreated without cellulase. It was also found that the improvement of the enzymolysis had a direct relevance with the amount of cellulase used during the SC-CO2 pretreatment. The moisture content of cellulose before SC-CO2 pretreatment had an obvious influence on the subsequent enzymolysis. When the moisture content of cellulose was 60% (W/W), the reducing sugar yield was higher than when the moisture content was over 100% (W/W). The FT-IR spectra showed that the structure of the cellulose pretreated with cellulase under the SC-CO2 condition was different from that of the cellulose pretreated without cellulase. In the presence of the enzyme, the strength of the hydrogen bonds and the I beta phase at 710cm(-1) in the crystalline cellulose was weakened. These results suggest that the change in the cellulose structure induced by the SC-CO2 treatment favous the subsequent enzymolysis.

THE ROLE OF CELLOBIOSE IN CELLULOSE BIOLOGICAL DEGRADATION / 微生物学通报

This paper discusses the mechanism of cellobiose in fungal cellulase induction a nd repression, and its inhibition of cellulases hydrolytic activity. Depending on the research result of cellulose binding domain, our hypothesis is that the main function of Exo-1,4-?-glucanase is to destroy th e crystal structure of cellulose to facilitaty hydrolyzing of ?-1,4 glucosidic bonds. A new strategy for the efficient transformation of cellulose material is advanced at t he end.

STUDY ON LIQUID CONDITIONS IN SHAKING FLASKS FOR LACCASE PRODUCTION BY A WHITE ROT FUNGUS / 微生物学通报

A white-rot fungi Rigidoporus sp.W-1 which could produce laccase was isolated. The fermentation conditions in shaking flasks were investigated. The optimal carbon source was wheat bran and (NH 4) 2SO 4 was the optimal nitrogen source. The components of the medium were optimized by orthogonal experiment. When W-1 was cultured under the optimum conditions, the activity of laccase could get to 7.1U/mL in 7 days.A great amount of crude laccase could be obtained by adding fresh medium to the 7 days old mycelium.

A NOVEL STRATEGY FOR SCREENING MUTANT ENZYMES UNDER NON-GROWTH CONDITIONS / 微生物学通报

The technique of double-layered plate was developed for screening the library of mutant endoglucanase III from Trichoderma reesei generated by the method of directed evolution.The enzyme activity was determined according to the velocity of the formation of halos on the plates.Several mutants with higher activity than the wild type at low temperature or alkaline pH were obtained by using this strategy under different screening conditions.Further results of spectrophotometric determination of the activities of these mutants were consistent with the results of plate screening.The establishment of such strategy will broaden the applications of the directed evolution methods for improving the existing proteins to obtain useful enzymes with new properties for industrial applications.