Lignocellulose Pretreatment Based On Instant Catapult Steam Explosion

Biofuel as an alternative to replace fossil fuel was obtained from abundant and renewable lignocellulose. However, lignocellulose owned so strong recalcitrance that microbes could utilize them once be hydrolyzed into sugars through pretreatment and enzymatic hydrolysis. In particular, pretreatment focused on lignocellulosic deconstruction to produce substrates which was easily hydrolyzed into sugar. Instant catapult steam explosion (ICSE) was capable to improve lignocellulosic structure and component in 0.0875 s to expose materials from high pressure to atmosphere. In this study, ICSE was applied for lignocellulosic pretreatment to develop a green, high efficient and low cost pretreatment scheme.1. Response surface methodology regression analysis optimized the operation conditions of ICSE pretreatment on corn stalk. After enzymatic hydrolysis of pretreated corn stalk, obtained sugar yield were utilized to evaluate pressure, time and mass. Then a second order polynomial equation was formed with R2=0.8756. The optimal conditions of ICSE pretreatment were 3.5 MPa (pressure),50 s (time) and 60 g (mass) with sugar yield 54.37%. The structural changes showed that pretreated corn stalk were porosity, less crystalline and favorable to be hydrolyzed.2. Evaluate water content on ICSE process through enzymatic hydrolysis and composition. ICSE pretreated five different kinds of feedstock from sweet potato vine including fresh feedstock, drying feedstock, dried feedstock and feedstock soaked in water for 2,30 and 60 hours, respectively. Compared with dried feedstock, fresh feedstock were more easily to be affected by ICSE via significantly improvement of composition and sugar yield such as the sugar yield of fresh feedstock improved over 2.6 folds after ICSE pretreatment than untreated feedstock. This is significantly better than dried feedstock. In conclusion, ICSE prefer to treat fresh feedstock without drying process.3. The contrast between milling and ICSE process were evaluated to develop a new strategy for chemical pretreatment. Raw corn stalk (R-feedstock), milling treated corn stalk (M-feedstock), and ICSE treated corn stalk (I-feedstock) were separately treated by acid, alkali, alkali-acid, organic solvent and ionic liquid in terms of composition, enzymatic hydrolysis, structural transformation and energy cost. Compared with M-feedstock, I-feedstock could improve chemical reagents’ hydrolysis abilities and thus improve the glucose yield (7.12 folds-Ionic liquid). Then we further analyze factors caused the different results of I-feedstock and M-feedstock. The reduction of xylan and Crystallinity area of I-feedstock caused the improvement of samples’ accessibilities for enzyme and chemical reagents. Furthermore, energy requirements to obtain I-feedstock far less than M-feedstock, only occupied 5%～10% of latter one. Based on these discussion, a new strategy before chemical pretreatment using ICSE replace the role of milling to obtain high efficient and low cost feedstock for downstream processing was proposed.4. The relationship between the composition of ionic liquid and feedstock were investigated through the compositional change, enzymatic hydrolysis and structural analysis. Three kinds of ionic liquid:1-butyl-3-methylimidazolium chloride ([Bmim]Cl), 1-buty 1-3-methylimidazolium bromide ([Bmim]Br) and 1-octyl-3-methylimidazolium chloride ([Omim]Cl) were selected to pretreat the lignocellulosic parts of oilseeds:peanut husk, peanut straw and cole straw. Among the untreated materials, peanut straw with the highest sugar yield 54.31% and the lowest lignin content was considered as the preferable substrate for biofuels production. The effect of [Bmim]Cl on sugar yield was more significant, which lead to 85.43% sugar yield for peanut straw. The structural changes were also analyzed and found that peanut straw’s morphological structure was distinctive with broken surface, incompact structural and lower crystallinity and all material turned to be more porous and rough than before. The results also showed that the chlorine and [Bmim]+ were vital on the effect of ionic liquid pretreatment.