Erratum to “Chloride assisted leaching of chalcocite by oxygenated sulphuric acid via Cu(II)–OH–Cl” [Miner. Eng. 20 (2007) 1075–1088]

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• 作者：G. Senanayake
• 关键词：Wood-decay fungus ; Endoglucanase ; Purification ; Characterization ; Daldinia eschscholzii
• 刊名：Minerals Engineering
• 出版年：2008
• 出版时间：April 2008
• 年：2008
• 卷：21
• 期：5
• 页码：421
• 全文大小：70 K

文摘

A thermostable endoglucanase was purified to homogeneity from culture supernatants of the wood-decaying fungus Daldinia eschscholzii (Ehrenb.:Fr.) Rehm grown on 1.0 % (w/v) carboxymethyl-cellulose using ammonium sulfate precipitation, ion-exchange, hydrophobic interaction, and gel filtration chromatography. The molecular weight of the enzyme was 46.4 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isoelectric point of the enzyme was at pH 4.9. The temperature for maximum activity was 70 °C, with 85 % of its maximum activity retained after 150 min of incubation at 50 °C, but was rapidly inactivated at 70 °C. The pH optimum of the enzyme activity was 6.0, and it was stable over a pH range of 4.0–7.0 at 50 °C. The enzyme was significantly inhibited by Hg²⁺, Cu²⁺, and Fe²⁺, and stimulated by Ca²⁺, Co²⁺, Mg²⁺, Mn²⁺, glycerol, DMSO, DTT, and EDTA. The enzyme also hydrolyzed filter paper, and Avicel^® PH-101 at rates of 25.8 % , and 7.3 % , respectively when compared with carboxymethyl-cellulose. The enzyme did not hydrolyze soluble starch, oat spelt xylan, birch wood xylan, or locust bean gum. The enzyme catalyzed the hydrolysis of carboxymethyl-cellulose with a K_m of 1.74 mg/ml and a V_max of 0.63 U/min/mg protein. This enzyme was competitively inhibited by glucose and cellobiose with K_i values of 0.67 and 0.45 M, respectively. TLC showed that the endoglucanase produces cellotetraose, cellotriose, cellobiose, and a small amount of glucose. The deduced internal amino acid sequences of the D. eschscholzii endoglucanase showed similarity to the sequences of the glucosyl hydrolase family 5.