Biorefinery Of Eucalyptus Chips By Autohydrolvsis For Producing Xylooligosaccharide

Based on the lignocellulosic biorefinery concept, the research aimed at extractingvalue-added hemicellulose products prior to kraft pulping. Firstly, the RSA experiment wasdesigned under3easy-to-control independent variables in plants such as the liquid-solid ratio,the highest temperature and the holding time based on the Box-Benhnken experimental designprinciples with the Design-Expert software; Secondly, the simulation of extracorporealcirculation cooking operated at continuous conditions by PID intelligent temperature controlerto optimize the relative content of xylo-oligosaccharides in hydrolysate, combined with theresponse surface model and P factor model; Thirdly, the xylooligosaccharide products can meetthe standard of GB/T23747-2009after clarification by ultrafiltration, efficient decoloriztionprocess, membrane enrichment and vacuum drying. The xylooligosaccharide products havegood thermal stability and proliferation effect of bifidobacterium adolescentis which providednew promising way for the lignocellulosic biorefinery concept achieved in pulping industry.(1)Combined the RSA experiment with the Design-Expert software, the auto-hydrolysisprocess of eucalyptus hemicellulose got an optimal condition: the liquid-solid ratio of13.81,the maximum temperature of184.62℃, and the holding time of103.01min,with a maximumresponse value of0.1331g/g in this condition. In order to verify the reliability of the optimalcondition, the actual conditions that the liquid-solid ratio of14, the highest temperature of185℃and the holding time of100min reached an average amount of0.1311g/g and61.24%hemicelluloses can be got with the form of reducing sugar. Furthermore, the monose andoligose contents in hydrolysate proved that the autohydrolysis process is suitable forhemicelluloses pre-extraction prior to pulping in wood-based biorefinery system.(2)The conditon of low temperature with long holding time is equal to high temperaturewith short time for extracting reducing sugar, such as R (153℃,153min)≈R (162℃,30min), R (158℃,158min)≈R (168℃,30min), R (164℃,164min)≈R (176℃,30min). In a given certain range (P<2500), the P-factor has a linear relationship with the response value R (g reducing sugar/g oven-dry wood). The extraction temperature of170℃canprovide better conversion of valuable XOS (about55%) and xylose in wood-based biorefinerysystem, especially for the autohydrolysis condition (170℃,40min；P-factor about1000).Combined with HPAEC-PAD, GC-MS and FT-IR, the increase of autohydrolysis intensity, alow degree of polymerization of xylan can further degradated into a small quantity of furfuraland other minor degradation products.(3)Experimental results showed that the selected powder activated carbon(AC7)adsorption combined with PAANa flocculation can reach high decoloriztion ratio with goodsugar retention and special mechanism. Besides, the furfural and lignin removal ratio reachesalmost100%and76.5%separately. Combined with IC, SEM, FT-IR, GC-MS and ICP-AESanalysis of the hydrolysate and pigment in sediment, it proved that lignin and its degradationproducts greatly contributed to coloring. The xylooligosaccharide products can meet thestandard of GB/T23747-2009after clarification by ultrafiltration, efficient decoloriztionprocess membrane enrichment and vacuum drying.(4)The TG-DSC results showed that xylo-oligosaccharides did not change when thetemperature is below236.9℃with good thermal stability. The proliferation staged with theadaptation (0-6h), logarithmic growth (6-24h) and stagnation (24-48h). Concentration ofbacteria in culture medium B peaked at1.31g/L at24with13.81times of proliferation and pHfrom6.50down to4.34. After the detoxification and decoloring process, the proliferationeffect of culture medium B is obvious. The metabolism products of bifidobacteriumadolescentis is mainly consisted of lactic acid, acetic acid and propionic acid. Early in the staticculture, the metabolism yield of acetic acid, propionic acid is higher than lactic acid. With theextension of incubation time for about12h, the concentration of propionic acid graduallystabilized, and the lactic acid, acetic acid became the main metabolism products.