Production of high activity <i>Aspergillus niger</i> BCC4525 β-mannanase in <i>Pichia pastoris</i> and its application for mannooligosaccharides production from biomass hydrolysis

<p>A cDNA encoding β-mannanase was cloned from <i>Aspergillus niger</i> BCC4525 and expressed in <i>Pichia pastoris</i> KM71. The secreted enzyme hydrolyzed locust bean gum substrate with very high activity (1625 U/mL) and a relatively high <i>k</i>_cat/<i>K</i>_<i>m</i> (461 mg⁻¹ s⁻¹ mL). The enzyme is thermophilic and thermostable with an optimal temperature of 70 °C and 40% retention of endo-β-1,4-mannanase activity after preincubation at 70 °C. In addition, the enzyme exhibited broad pH stability with an optimal pH of 5.5. The recombinant enzyme hydrolyzes low-cost biomass, including palm kernel meal (PKM) and copra meal, to produce mannooligosaccharides, which is used as prebiotics to promote the growth of beneficial microflora in animals. An <i>in vitro</i> digestibility test simulating the gastrointestinal tract system of broilers suggested that the recombinant β-mannanase could effectively liberate reducing sugars from PKM-containing diet. These characteristics render this enzyme suitable for utilization as a feed additive to improve animal performance.</p> <p>A recombinant β-mannanase from <i>A. niger</i> BCC4525 exhibits high activity. It produces MOS from low-cost biomass and enhance the release of reducing sugars from diet.</p