Genome mining and motif truncation of glycoside hydrolase family 5 endo-β-1,4-mannanase encoded by Aspergillus oryzae RIB40 for potential konjac flour hydrolysis or feed additive

Two novel glycosyl hydrolase family 5 (GH5) β-mannanases (AoMan5A and AoMan5B) were identified from Aspergillus oryzae RIB40 by genome mining. The AoMan5A contains a predicted family 1 carbohydrate binding module (CBM-1), located at its N-terminal. The AoMan5A, AoMan5 B and truncated mutant AoMan5AΔCL (truncating the N-terminal CBM and linker of AoMan5A) were expressed retaining the N-terminus of the native protein in Pichia pastoris GS115 by pPIC9 KM. The specific enzyme activity of the purified reAoMan5A, reAoMan5 B and reAoMan5AΔCL towards locust bean gum at pH 3.6 and 40 °C for 10 min, was 8.3, 104.2 and 15.8 U/mg, respectively. The temperature properties of the reAoMan5AΔCL were improved by truncating CBM. They can degrade the pretreated konjac flour and produce prebiotics. In addition, they had excellent stability under simulative gastric fluid and simulative prilling process. All these properties make these recombinant β-mannanases potential additives for use in the food and feed industries.