Study On Effective Pretreatment And Efficient Utilizations Of Cellulosic Polysaccharide Material

The threat of global warming,along with continuing population growth,has driven the world to increasingly utilize environmentally-friendly energy sources.Bioethanol is the most important biofuel today,which accounts for more than 90%of total biofuel use.Lignocellulose is a complex microstructure composed of cellulose,hemicellulose and lignin.It is important to develop the coupling technology of raw materials to produce bioethanol,to improve the production efficiency,to increase the economic benefits of the production process,and to broaden the development direction of sugar platform to achieve the comprehensive utilization of products.Cellulosic polysaccharide materials(furfural residue,cassava residue and moso bamboo)are potential raw materials for large-scale production of bioethanol.In this paper,the pretreatment of furfural residues(FR)with green liquor and hydrogen peroxide was studied.The pretreated FR was coupled with cassava residues(CR)to produce ethanol by co-fermentation.The bamboo was treated with glycerol,a by-product of biodiesel production,at a relatively mild temperature.The effects of different post-treatment methods for removing residual glycerol from the substrate on subsequent enzymatic hydrolysis and fermentation were discussed.Phenol-dioxane system was used to treat moso bamboo to achieve efficient separation and utilization of the three major compositions of bamboo.The obtained enzymatic hydrolysate of bamboo or saccharification liquid of CR could be used as a good substitute for the carbon source of glucose in the culture medium of Acetobacter xylinum.The optimum conditions for the production of functional composite bacterial cellulose hydrogel as a good excipient for drug-sustained release were explored.CR and FR were compared during simultaneous saccharification and fermentation(SSF)for ethanol production due to their value-added applications and positive environmental impacts.A potential commercial pretreatment for FR was investigated by using a combination of green liquor and hydrogen peroxide(GL-H2O2).Our results indicate that 42.0%of FR lignin removal was achieved on FR using of 0.6 g H2O2/g-substrate and 2 mL GL/g-substrate at 80?.The GL-H2O2 pretreated FR was evaluated for SSF.The highest overall ethanol yield(93.6%of the theoretical),equivalent to an ethanol concentration of 39.9 g/L,was achieved using a combination of 0.6 g/g-H2O2-GL-pretreated FR and CR at a ratio of 1:1 with 12%substrate loading.Using 0.6 g/g-H2O2-GL-pretreated FR with CR at a ratio of 2:1 with high substrate loading(20%)resulted in a decreased yield(79.2%),while the ethanol concentration increased to 51.9 g/L.Moreover,FR pretreated with GL-H2O2 decreased the concentration of byproducts(glycerol,lactic acid,and acetic acid)in SSF compared with that obtained in the previous study.Compared to delignification,the addition of surfactants is the method that could improve enzymatic hydrolysis with a lower cost.The highest overall ethanol concentration(56.6 g/L),which is equivalent to an ethanol yield of 86.3%of the theoretical,was achieved using a combination of FR with high intensity delignification and cassava residues at a ratio of 2:1 under 20%substrate loading with Sapindus mukurossi saponin of 0.5 g/L.Cassava residues promote furfural residues by providing important nutrients for fermentative organisms,and in turn furfural residues promote cassava residues by providing cellulosic enzymes.Moso bamboo was pretreated with industrially derived crude glycerol obtained from different sources at 150/160? for 3 h.This bamboo,pretreated with base biodiesel glycerol with pressure filtration removal method(BBGP),showed a high glucose yield of 95.0%and an ethanol yield of 73.1%of the theoretical.Major glycerol content was removed by pressure filtration,leaving a small amount of fatty acid soap in the pretreated sample,which formed an emulsion that reduced lignin redisposition onto the biomass surface and effectively blocked lignin absorption of cellulase,allowing greater enzymatic hydrolysis and fermentation system function.The surface was more hydrophilic and a higher lignin removal was achieved:39.2%with biodiesel glycerol(BBG)pretreatment compared to 26.1%with sodium hydroxide glycerol(SG)pretreatment.This study provides a useful and cost-effective process,BBGP,for high-yield ethanol production.Hemicellulose was depolymerized to furfural with hydrochloric acid as a catalyst to obtain a yield of 93.5%of the theoretical value in the acidic 1,4-dioxane system,whereas the cellulose pulp remained in a solid state at mild temperatures from 80? to 120?.The separated lignin was dissolved and phenolated in an aqueous solution,and the fractionated lignin yield was 51.9%at 80? for 2 h in the presence of 25%phenol(wt%of substrate)and 900 mL 1,4-dioxane dosage.The phenolated lignin could potentially be used as a low-cost substitute for phenol in phenol-formaldehyde reactions.The delignified cellulose could be directly subjected to enzymatic hydrolysis,resulting in a glucose yield of 99.0%.Overall,a selective and efficient pretreatment of lignocellulose fractionation was achieved under environment-friendly and mild conditions.The hydrolysate of pretreated bamboo or saccharification liquid of CR could be used as good substitutes for carbon source of Acetobacter xylostella culture medium to produce bacterial cellulose.HA-BBC,HA-CBC or AA-BBC,AA-CBC composite hydrogels were obtained by adding 1.5%HA or 0.5%AA through in-stu synthesis.The pyrolysis performance of HA-CBC was the best.AA-CBC has good drug loading and drug sustained release performance.It can extend bovine serum albumin(BSA)release cycle after 60 h and 95%of the drug was released.Composite BC hydrogels have good cell compatibility with Hela cells.Therefore,the composite hydrogels in this study have good biocompatibility and can be used in drug delivery system.