| 1. |
- Krogh, K.B.R.M., et al.
(författare)
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Characterization and kinetic analysis of a thermostable GH3 β-glucosidase from Penicillum brasilianum
- 2010
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598. ; 86:86, s. 143-154
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Tidskriftsartikel (refereegranskat)abstract
- A GH3 β-glucosidase (BGL) from Penicillum brasilianum was purified to homogeneity after cultivation on a cellulose and xylan rich medium. The BGL was identified in a genomic library, and it was successfully expressed in Aspergillus oryzae. The BGL had excellent stability at elevated temperatures with no loss in activity after 24 h of incubation at 60°C at pH 4-6, and the BGL was shown to have significantly higher stability at these conditions in comparison to Novozym 188 and to other fungal GH3 BGLs reported in the literature. The BGL had significant lower afinity for cellobiose compared with the artificial substrate para-nitrophenyl-β-D-glucopyranoside (pNP-Glc)and further, pronounced substrate inhibition using p-NP-Glc. Kinetic studies demonstrated the high importance of using cellbiose as substrate and glucose as inhibitor to describe the inhibition kinetics of BGL taking place during cellulose hydrolysis. A novel assay was developed to characterize this glucose inhibition on cellobiose hydrolosis. The assay uses labelled glucose-13C6 as inhibitor and subsequent mass spectrometry analysis to quantify the hydrolysis rates
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| 2. |
- Krogh, K.B.R.M., et al.
(författare)
-
Cloning of a GH5 endoglucanase from genus Penicillium and its binding to different lignins
- 2009
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Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; :44, s. 359-367
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Tidskriftsartikel (refereegranskat)abstract
- The cel5C gene, coding for an endoglucanase (Cel5C) of Penicillium brasilianum was cloned and heterologously expressed in Aspergillus oryzae. This is only the second GH5 EG from the genus Penicillium reported in the CAZy database. The promoter region of the gene has putative binding sites for both the carbon catabolite repressor CreA and the activator XlnR. The pH optimum of Cel5C was found to be 4.0 and the temperature optimum was 70°C. At a typical temperature for lignocellulose hydrolysis Cel5C retained full residual activity after 20 h of incubation at pH 5.0 and 6.0. Adsorption to Avicel and steam pretreated spruce, was found to follow the Langmuir isotherm, and the maximum adsorption was similar for both substrates, 40 and 49 mg/g, respectively. The affinity for Avicel was 10 times higher than for steam pretreated spruce, 0.040 and 0.0035 L/mg, respectively. Non-productive binding of cellulolytic enzymes to lignin is an important obstacle to overcome for commercial biomass to ethanol production. Therefore, the adsorption on residual lignin produced from various biomass samples was investigated. Both substrate and pretreatment conditions resulted in different adsorptions of Cel5C to residual lignin.
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