Recombinant Production and Biochemical Characterization of Thermostable N-arabinofuranosidase from Acidothermophilic Alicyclobacillus acidocaldarius

Abstract

Enzymes are successfully used in many industrial process, such as food and paper industries. Enzymes, which are derived from microorganisms living under mild conditions, are not suitable for industrial processes performed at high temperature, acidic or basic reaction conditions. Thus, enzymes derived from extremophilic microorganisms are needed for these hard industrial conditions. Alicyclobacillus acidocaldarius DSM 446 with an optimum growth temperature of 60–65°C, is an acidothermophilic bacterium that grows in acidic hot springs. In addition to growth in both acidic and hot springs, having a complete genome project makes the organism an important source for enzymes that are used in harsh industrial conditions. Arabinofuranosidases (E.C 3.2.1.55; AFases) belong to glycoside hydrolase family enzymes. AFases hydrolyzes 1,3- and 1,5-α-arabinosyl bounds of L-arabinose containing molecules. L-arabinoses are present in hemicellulosic part of lignocellulosic biomass. AFases also play an important role in the complete hydrolysis of arabinoxylans. Analysis of the genome project and CAZY database revealed two putative arabinofuranosidase genes in the A. acidocaldarius genome. In this study, we aimed cloning, heterologous expression, purification and biochemical characterization of the α-N-Arabinofuranosidase enzyme encoded in A. acidocaldarius genome. For this purpose, the gene of α-N-Arabinofuranosidase protein was cloned into pQE-40 vector and expressed heterologously in E. coli BL21 GOLD (DE3). Biochemical characterization of the purified enzyme revealed that A. acidocaldarius α-N-Arabinofuranosidase enzyme showed optimum activity at 45 ºC and pH 6.5 in phosphate buffer. Furthermore, enzyme has 60% activity after 90 min. incubation at 80 ºC. A. acidocaldarius α-N-Arabinofuranosidase enzyme has high potential to be used as accessory enzyme for the complete degradation of arabinoxylans.