NOVELTY - A recombinant polypeptide (A1) having beta -mannanase activity is new.    USE - As recombinant polypeptide having beta -mannanase activity for hydrolyzing a lignocellulosic biomass substrate containing galactoglucomannan and/or glucomannan; for degrading or converting a cellulosic material into fermentable sugars (claimed).    ADVANTAGE - The polypeptide improves the hydrolysis performance of a cellulase composition when the polypeptide constitutes up to 20 wt.% of the cellulase composition, where the improved hydrolysis performance includes: an increased glucan conversion percentage, an increased xylan conversion percentage, and/or an increased glucan and xylan conversion percentage from a given lignocellulosic biomass substrate under the same hydrolysis conditions; or at least 5% faster viscosity reduction of a given lignocellulosic biomass substrate under the same hydrolysis conditions. The polypeptide has an increased beta -mannanase activity as compared to the beta -mannanase activity of ScoMan1 (Streptomyces coelicolor A3 beta -mannanase) comprising a sequence containing 384 amino acids (SEQ ID NO: 4) as given in the specification; beta -mannanase activity of Bsp Man1 (Bacillus caldovelox beta -mannanase) comprising a sequence containing 694 amino acids (SEQ ID NO: 5) as given in the specification, or beta -mannanase activity of Msp Man2 (Micromonospora sp. L5 beta -mannanase) comprising a sequence containing 462 amino acids (SEQ ID NO: 6) as given in the specification. The polypeptide retains greater than 70% of the beta -mannanase activity when incubated at a pH of 4.2-7.8; and the polypeptide has optimum beta -mannanase activity at a pH of 5.0. The polypeptide retains at least greater than or equal to 80% of the beta -mannanase activity when incubated at 58-78 degrees C; has optimum beta -mannanase activity at 71 degrees C; retains at least 50% of the beta -mannanase activity when incubated for 2 hours at 72 degrees C; or retains at least 99% of the beta -mannanase activity when incubated for 2 hours at up to 60 degrees C. The highly active beta -mannanase (Tfu Man1) isolated from the bacterial species Thermobifida fusca (Tfu Man 1) strain YX, can hydrolyze a lignocellulosic biomass substrate. When such a polypeptide is combined with cellulases and/or other hemicellulases confer improved capacity of that composition or mixture to hydrolyze of lignocellulosic biomass substrates. Such improvements include, an increased glucan conversion, an increased glucose yield from a given biomass substrate, an increased xylan conversion, an increased xylose yield, an increased total soluble sugar yield from a given biomass substrate, a more rapid liquefaction of a given biomass substrate at a solids level, and a more rapid viscosity reduction of a biomass substrate at a solids level. Such a polypeptide can be used to boost the cellulosic biomass conversion and hydrolysis when in combination with a cellulase mixture or composition, which optionally further comprises other hemicellulase. The Tfu Man1 polypeptides and compositions comprising Tfu Man1 polypeptides have improved efficacy at conditions under which saccharification and degradation of lignocellulosic biomass take place.    DETAILED DESCRIPTION - A recombinant polypeptide (A1) having beta -mannanase activity comprising an amino acid sequence that is at least 65% identical to the amino acid sequence of a sequence containing 453 amino acids (SEQ ID NO: 2) as given in the specification, or a sequence containing 425 amino acids (SEQ ID NO: 3) as given in the specification, is new. INDEPENDENT CLAIMS are included for the following:    (1) an enzyme composition comprising the recombinant polypeptide (A1) and at least one cellulase or hemicellulase;    (2) a nucleic acid encoding the recombinant polypeptide (A1);    (3) an expression vector comprising the nucleic acid in operable combination with a regulatory sequence;    (4) a host cell comprising the expression vector;    (5) a composition (C1) comprising the host cell and a culture medium;    (6) producing (M1) beta -mannanase involving culturing the host cell in a culture medium, under suitable conditions to produce the beta -mannanase;    (7) a composition (C2) comprising the beta -mannanase produced in accordance with the method (M1) in supernatant of the culture medium;    (8) hydrolyzing a lignocellulosic biomass substrate involving contacting the lignocellulosic biomass substrate with the polypeptide (A1), or the composition (C1) or (C2), to yield glucose and other sugars; and    (9) a composition (C3) comprising the recombinant polypeptide and a lignocellulosic biomass substrate.