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Over-expression and characterization of the alkalophilic, organic solvent-tolerant, and thermotolerant endo-1,4-β-mannanase from Bacillus licheniformis isolate THCM 3.1

Pornpimon Kanjanavas^a, Paisarn Khawsak^a, Arda Pakpitcharoen^a, Supatra Areekit^a, Thayat Sriyaphai^a, Khajeenart Pothivejkul^b, Somchai Santiwatanakul^c, Kenji Matsui^d, Tadahiko Kajiwara^d, Kosum Chansiri^a,*

 
ABSTRACT:     Gene encoding for endo-1,4-β-mannanase (EC 3.2.1.78) from Bacillus licheniformis THCM 3.1 was cloned and over-expressed in pET 100/D TOPO vector. The molecular weight of the purified enzyme was about 40 kDa. This enzyme had an optimum pH of 9 and an optimum temperature of 45 °C and retained up to 77% of its activity after incubation for 48 h. The activity of the enzyme was inhibited by 10 mM of Pb²⁺, Ag⁺, Fe³⁺, Sn²⁺, Cu²⁺, and EDTA. Although partially inhibited, the enzyme retained much of its activity when the reaction solution was mixed with 15% (v/v) of the organic solvents acetone, toluene, benzene, dimethyl sulphoxide, 2-propanol, acetonitrile, or cyclohexane.

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* Corresponding author, E-mail: kosum@swu.ac.th

Received 29 Apr 2008, Accepted 6 Feb 2009