The Effect Of Combined Order In Integrated Processes Of Steam Explosion And Alkaline Pretreatment On The Structure Of Lignocellulosic Materials And Its Enzymatic Hydrolysis

In order to study the effect of alkaline pretreatment on the structure and enzymatic hydrolysis of different substrates characteristics, C. korshinskii Kom(abbreviation for CKK) and wheat straw were used as raw materials by alkaline pretreatment at ambient temperature and high temperature, respectively. The changes of surface morphology and chemical composition of the materials were analyzed by SEM and FRIT. The pretreated biomass was used to carry out enzymatic hydrolysis. SEM images showed that the NaOH pretreatment can effectively remove the composition of the lignin, and destroy the dense physical structure. The results from the FTIR spectrometry indicated that the structures of lignin in wheat straw and CKK were damaged after alkaline pretreatment, some functional groups such as hydroxyl, methylene, methoxy and ester bonds were broken. Temperature plays an important role in affecting alkaline pretreatment. When temperature increased,NaOH solution was able to remove the content of lignin and seriously destroy the physical structure of substrates. Hence, the effect of increasing temperature can promote alkaline pretreatment.Various combined processes of steam explosion and alkaline pretreatment were experimentally compared and evaluated on same wheat straw and CKK materials. The morphological characterizations of pretreated wheat straw and CKK were performed by a scanning electron microscope and FTIR spectroscopy, to qualitatively determine the composition changes of pretreated wheat straw. Comparing to the single process or the combination of alkaline pretreatment followed by steam explosion (ASP), the steam explosion followed by alkaline process (SAP) pretreatment removed most of lignin, degraded hemicelluloses, and incurred a higher surface area of the cellulose-rich substrates. And remaining contents of cellulose, xylan and lignin in SAP wheat straw were 88.15%, 5.55%,4.13%, respectively, and 65.36%, 7.90%, 17.94% in SAP CKK. Moreover, SAP enhanced the fed batch enzymatic hydrolysis of cellulose-rich substrates to a maximum value of 80.53%and 60.84% even at the high cellulose loading of 18% and 15%, SAP wheat straw achieved the final glucose concentration of 143.59 g/L, especially. The results indicated that, the SAP process is advantageous scheme for the enhancement of enzymatic efficiency.During the process of SSF in which the SAP wheat straw and CKK were employed as substrate at a glucan loading of 4% and 6% (w/v), respectively. An ethanol yield of 60% and 50% (theoretical) was respectively achieved when the SSF process was carried out at 35?and 150 rpm for 24 hours. While the final ethanol concentration was 24.12 g/L (70.77%ethanol yield) and 13.09 g/L (57.63% ethanol yield) at 72 h of SSF process, respectively. The results showed that the pretreatment of SAP can also enhance the SSF process, benefited from the enriched glucan component in pretreated wheat straw and CKK by SAP.