Abstract: An apparatus for treating plant biomass is described herein. Generally, the apparatus includes a pressurizable vessel and a heating element in thermal communication with the vessel. Also described herein are methods of treating plant biomass. Generally, the methods include heating plant biomass under conditions effective to at least partially depolymerize hemicellulose and/or cellulose present in the plant biomass. In one embodiment, the method includes heating a plant biomass substrate to a temperature of 230° C. for two minutes at a pressure of 57 psig.