NOVELTY - The enzymatic reactor apparatus comprises an internal mixing chamber, a rotating mixing device, an biomass inlet (22) of first conical mixing chamber, a first conical mixing chamber, and a second reactor chamber. The internal mixing chamber includes a first chamber section. The first conical mixing chamber has a cross-sectional area expanding from the biomass inlet for the internal mixing chamber to the second cylindrical chamber, and has a volume of 50 cubic meters and a retention time of 2-4 hours. The second chamber section has a uniform internal cross-sectional area.    USE - The enzymatic reactor apparatus is useful for mixing a biomass with an enzyme to promote hydrolysis, for fermentation of biomass to bioalcohols such as ethanol or butanol, for forming bio-gas, for forming specialty carbohydrates for food and feed, forming carbohydrate feedstock, and for processing biomass into plastics and chemicals, where the enzyme includes cellulose, a thermophilic bacterium or other cellulose degrading organism or biocatalyst (claimed).    ADVANTAGE - The efficient enzymatic reactor apparatus rapidly mixes the enzymes with the biomass with high fibrous or mud-like consistency thus reducing viscosity of the biomass.    DETAILED DESCRIPTION - The enzymatic reactor apparatus comprises an internal mixing chamber, a rotating mixing device, a biomass inlet (22) of first conical mixing chamber, a first conical mixing chamber, and a second reactor chamber. The internal mixing chamber includes a first chamber section. The first conical mixing chamber has a cross-sectional area expanding from the biomass inlet for the internal mixing chamber to the second cylindrical chamber, and has a volume of 50 cubic meters and a retention time of 2-4 hours. The second chamber section has a uniform internal cross-sectional area from an opposite end of the first chamber section to a discharge end of the mixing chamber, and receives a biomass from a biomass outlet of the first conical mixing chamber. The biomass inlet is coupled to a source of pre-treated biomass and an enzyme external to a reactor vessel (10), receives the biomass and the enzyme as a mixture, and is placed at an upper/lower elevation of the apparatus. The rotating mixing device is placed in the internal mixing chamber and coaxial with an axis of the first chamber section, and includes arms extending radially out from a rotating shaft (16) coaxial with the axis. The cross-sectional area of the first chamber increases linearly. The first chamber and the second chamber are placed within a single reaction vessel. The first chamber is placed above the second chamber. The apparatus has a vertical axis. The discharge end is placed at a lower/upper elevation of the apparatus. The first conical mixing chamber and second reaction chamber are continuous flow chambers, and have a combined retention time of 2-4 hours and combined volume of 50 cubic meters. An INDEPENDENT CLAIM is included for method to mix biomass and an enzyme in a reactor and mixing apparatus.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic cross-sectional view of a vertically aligned mixing and hydrolysis reaction vessel for biomass.    Reactor vessel (10)    Conical upper section (12)    Cylindrical lower section (14)    Rotating shaft (16)    Biomass inlet. (22)