Mannan endo-1,4-beta-mannosidase that exhibits high activity against konjac glucomannan and carob galactomannan, as well as a lower activity toward beta-mannan (PubMed:27193267). Shows no activity against barley beta-glucan, birchwood xylan, and low viscosity carboxymethyl cellulose (CMC) (PubMed:27193267). Has the ability to hydrolyze manno-oligosaccharides such as M4 which is degraded slightly to M3 and M1, M5 which is mainly degraded to M4 and M1, and M6 which is mostly hydrolyzed to M4 and M2 (PubMed:27193267). Shows no activity toward M2 and M3 manno-oligosaccharides (PubMed:27193267). The activity is completely impaired by Ag(+), partially inhibited by Zn(2+), and enhanced by Co(2+), Ni(2+) and Cu(2+) by 22.6, 14.5 and 20.8 %, respectively (PubMed:27193267). Ca(2+), Na(+), Mg(2+), Mn(2+), urea and EDTA do not significantly affect the mannanase activity (PubMed:27193267). Optimum pH is 6.0. Optimum temperature is 60 degrees Celsius. The addition of Man26A as a supplement to the commercial enzyme mixture Celluclast(R) 1.5 L and Novozyme(R) 188 results in enhanced enzymatic hydrolysis of pretreated beechwood sawdust, improving the release of total reducing sugars and glucose by 13 and 12 %, respectively. Belongs to the glycosyl hydrolase 26 family.