beta-Mannosidase (EC 3.2.1.25) is an exoglycosidase specific for the hydrolysis of terminal beta-1,4-glycosidic linkage in mannan which can be applied in the food manufacture, animal feed, bioethanol making and coffee extraction industries. A novel beta-mannosidase gene (Lrman5A) from Lichtheimia ramosa was synthesized and recombinantly expressed in Pichia pastoris X33. Lrman5A encodes 444 amino acids with a calculated molecular mass of 51.0 kDa which shares the highest identity (73%) with the beta-mannosidase from Rhizomucor miehei. Purified recombinant Lrman5A showed the maximal activity at pH 6.0 and 65 degrees C, had broad-range pH stability (retaining >65% activity after incubation at pH 3.0-8.5 at 37 degrees C for 24 h), and was highly thermostable (retaining >80% activity after incubation at 65 degrees C for 10 min). The specific activity, and Km of Lrman5A was 17.5 U/mg and 1.377 mM, respectively. Lrman5A and GH5 beta-mannanase displayed significant synergistic effects on the degradation of locust bean gum (LBG) and released more mannose (up to 2.89 folds) by simultaneous or sequential addition. Due to its hydrolytic properties, Lrman5A may have potential applications in the area of bioenergy, feed and food processing. (C) 2019, The Society for Biotechnology, Japan. All rights reserved.