the ph and acetic acid is present in the gaseous effluent the design of the reactor is described in u s pat no 4 461 648 hereby incorporated by reference additionally canadian patent ca 1 212 505 describes the application of a combination of the stake and iotech steam explosion processes to obtain paper paste from hard wood with high yields the fundamental objective of pretreatment is to reduce the crystallinity of the cellulose and to dissociate the hemicellulose cellulose complex the digestibility of the cellulose typically increases with the degree of severity of the pretreatment this increase in digestibility is directly related to the increase in the available surface area asa of the cellulose materials which facilitates the eventual enzymatic attack by cellulases the increased accessibility of the substrate after steam pretreatment treatment appears to be due to changes in the distribution of pore size the degree of crystallinity the degree of polymerization and or the residual xylan content which determine its final effectiveness k k y wong et al biotechnol bioeng 31 447 1988 h l chum et al biotechnol bioeng 31 643 1988 while early researchers focused their work on the effects of sudden de pressurization on the rupture of cellulose bonds in experiments at high temperatures 220 u00b0 c to.