Expression and Characterization of a GH16 Family β-Agarase Derived from the Marine Bacterium <i>Microbulbifer</i> sp. BN3 and Its Efficient Hydrolysis of Agar Using Raw Agar-Producing Red Seaweeds <i>Gracilaria sjoestedtii</i> and <i>Gelidium amansii</i> as Substrates

• Main Authors: Ren Kuan Li, Xi Juan Ying, Zhi Lin Chen, Tzi Bun Ng, Zhi Min Zhou, Xiu Yun Ye
• Format: Article
• Language: English
• Published: MDPI AG 2020-08-01
• Series: Catalysts
• Subjects: agarase; <i>Microbulbifer</i> sp. BN3; enzymatic hydrolysate
• Online Access: https://www.mdpi.com/2073-4344/10/8/885

Agarases catalyze the hydrolysis of agarose to oligosaccharides which display an array of biological and physiological functions with important industrial applications in health-related fields. In this study, the gene encoding agarase (Aga-ms-R) was cloned from <i>Microbulbifer</i> sp. BN3 strain. Sequence alignment indicated that Aga-ms-R belongs to the GH16 family and contains one active domain and two carbohydrate binding module (CBM) domains. The mature Aga-ms-R was expressed successfully by employing the <i>Brevibacillus</i> system. Purified rAga-ms-R was obtained with a specific activity of 100.75 U/mg. rAga-ms-R showed optimal activity at 50 °C and pH 7.0, and the enzyme activity was stable at 50 °C and also over the pH range of 5.0–9.0. After exposure of rAga-ms-R to 70 °C for 30 min, only partial enzyme activity remained. Thin layer chromatographic analysis of the enzymatic hydrolysate of agar obtained using rAga-ms-R disclosed that the hydrolysate comprised, in a long intermediate-stage of the hydrolysis reaction, mainly neoagarotetraose (NA4) and neoagarohexaose (NA6) but ultimately, predominantly neoagarotetraose and trace amounts of neoagarobiose (NA2). Hydrolysates of the raw red seaweeds <i>Gracilaria sjoestedtii</i> and <i>Gelidium amansii</i>, produced by incubation with rAga-ms-R, were mainly composed of neoagarotetraose. The results demonstrate the high efficiency of rAga-ms-R in producing neoagaraoligosaccharide under low-cost conditions.