Extraction of the readily hydrolyzable carbohydrates with hot water in the absence of added foreign chemicals is desirable for facilitating the utilization and the recovery of the hydrolyzate components. When heating values of the residual chips are to be recovered after extraction, there is no reduction in value due to caustic or metal hydroxides and no increase in corrosion from mineral acids. Furthermore, the environmental and recovery side effects are avoided as caustic or sodium is not added to the process streams and no byproducts from mineral acid neutralization are produced. The hot-water extraction process could be catalyzed by base, acid or Xylanase. Without caustic addition, hydrolyzed hemicelluloses produce acetic acid, in addition to sugars. This acidic condition during the hot-water extraction process further catalyzes the hydrolysis reactions. Therefore, the hot-water extraction reactions are autocatalytic. The extraction proceeds slowly initially and faster as pH decreases during the extraction. Recycle extracts or extract component can significantly increase the extraction rates. Efficient reactors can be designed to perform the hot-water extraction operations using existing processes of wood chips.