Characterization of a thermoalkalophilic esterase from a novel thermophilic bacterium, Anoxybacillus gonensis G2.
Poly-3-hydroxybutyrate (P3HB) degradation capabilities of a novel bacterium, Anoxybacillus gonensis G2, were investigated. Both changes on film surfaces of the solution-cast films monitored by scanning electron microscopy (SEM) and weight loss up to 24% after 72 h exposure to A. gonensis G2 cultures indicated secretion of an active esterase responsible for the degradation of P3HB films. Kinetic parameters, Vmax and Km for the esterase activity of crude enzyme from A. gonensis G2 in the presence of p-nitrophenylbutyrate as substrate were observed as 50 U/L and 0.125 mM, respectively, in 50 mM phosphate buffer, pH 7.5 at 60 degrees C. The stimulation of the activity by Ca2+ is an evidence for the requirement of Ca2+ as a cofactor for the enzyme activity which is a characteristic for lipases/esterases. Inhibition of the esterase activity by metal chelating agents such as ethylenediamine tetraacetate, azide and cyanide has also supported the requirement of a metal ion for the activity. The thermal and pH stability profiles for the enzyme showed that the thermophilic bacterium A. gonensis G2 secretes an extracellular thermoalkalophilic PHB depolymerase active at 60 degrees C, and stable at this temperature for 120 min at pH 7.5 and for 24 h at pH 7.5-9.5 range at 4 degrees C by retaining over 75% of its initial activities.
Colak
Ahmet
A
Department of Chemistry, Karadeniz Technical University, 61080 Trabzon, Turkey.
Sişik
Deniz
D
Saglam
Nagihan
N
Güner
Saadettin
S
Canakçi
Sabriye
S
Beldüz
Ali Osman
AO
D000704:Analysis of Variance; D001406:Bacillaceae / Q000201:enzymology*; D001673:Biodegradation, Environmental; D018441:Biofilms; D002118:Calcium / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D004950:Esterases / Q000037:antagonists & inhibitors / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D006885:Hydroxybutyrates / Q000378:metabolism*; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D011091:Polyesters / Q000378:metabolism*; D013696:Temperature; D000094122:Polyhydroxybutyrates
D002118:Calcium; D002614:Chelating Agents; D004950:Esterases; D006885:Hydroxybutyrates; D011091:Polyesters; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates