Biochemical characterization of a novel thermostable feruloyl esterase from Geobacillus thermoglucosidasius DSM 2542(T)

摘要

The ferulic acid esterase (FAE) gene from Geobacillus thermoglucosidasius DSM 2542(T) was cloned into pET28a(+) expression vector and characterized and is being reported in this study for the first time in Geobacillus. The enzyme, designated as GthFAE, was purified by heat shock and ion-exchange column chromatography. In addition, a second clone containing a Histidine tag was expressed and purified by affinity column chromatography demonstrating future potential for scale-up. FAE gene contains an open reading frame (ORF) of 759-bp encoding a hypothetical 252 amino acid protein, a molecular mass of 28.11kDa and an isoelectric point of 5.53. From this study it was found that GthFAE had optimal activity at 50 degrees C and pH of 8.5. Furthermore, the enzyme has been found to retain 64 of its activity after two days incubation at 50 degrees C and exhibited a high level of functionality with p-nitrophenyl caprylate (C8). K-m, V-max, k(cat) and k(cat)/K-m values for p-nitrophenyl caprylate were determined as 0.035mM, 11,735 mu mol/min/mg protein, 5491 (1/s) and 156,885s(-1)mM(-1) respectively. The combination of higher activity and stability compared to previously reported FAEs makes GthFAE a potential candidate for use in the paper manufacturing industry.