Investigation of steam explosion for polysaccharide recovery as a function of process severity

From the last several years, different pretreatment technologies have been developed and investigated. However, the viability of the pretreatment technology depends on the product that will be generated (liquid fuels, chemicals, etc). The steam explosion pretreatment (StEx) is the most ready for scaling up application on large scale, especially if the process focuses on cellulosic ethanol production. Here is shown a study focused on the identification of the critical parameters of the pretreatment of sugarcane bagasse (SCB) by StEx, that may lead to a higher C5 recovery and lower cellulose losses, as well as to produce a substrate with increased accessibility to the enzymes. The StEx experiments were carried out within severity (expressed as value of Combined Severity Factor-CSF) ranging from 0.14 to 1.02, using both sulfuric acid-catalyzed and auto-catalyzed experimental approaches. The unwashed pretreated materials were hydrolyzed using 20FPU of Cellic CTec3 (Novozymes^®) per gram of dry substrate and 20% of total solids. Results showed 90%-94% and 61%-73% of total C6 and C5 recoveries, respectively. Besides, no mathematical tendency was found for total C5 recovery versus CSF, but the ratio between mono and oligomeric forms followed a logarithmical behavior. No tendency was found between total monosaccharides produced after hydrolysis and CSF. The best results of polysaccharide recovery were found to be between 10 and 12 bar for 15 and 20 minutes of pretreatment, leading to over than 100g.L^-1 of monosaccharides after enzymatic hydrolysis.