Preparation And Application Of Nanocrystalline Cellulose From Moso Bamboo Pulp By Enzymatic Pretreatment

Nanocrystalline cellulose (NCC) is an emerging and renewable functional material, withnano-size and excellent performance, prepared from natural fiber by degradation. NCC hasbroad applications in many fields because of rich resources and low cost of raw materials.In this paper, moso bamboo pulp was prepared into three kinds of raw materials, respectivelybamboo pulp, bamboo pulp powder with180mesh and bamboo pulp powder (respectively thesample Ⅰ, sample Ⅱ and sample Ⅲ). NCC was prepared from three kinds of raw materials byacid hydrolysis. The yield of sample Ⅲ-NCC was52.5%with hydrolysis conditions: sulfuricacid concentration, hydrolysis time, temperature and solid-liquid ratio were respectively60%,90min,45℃and1:8. NCC was in two forms of rods analyzed with TEM, while sampleⅠ-NCC with length of about50-200nm and diameter of about10-30nm; sample Ⅱ-NCC andsample Ⅲ-NCC were with length of about50-150nm and diameter of about10-15nm.NCC was prepared from sample Ⅰ by enzyme pretreatment with cellulase Ⅰ combined withacid hydrolysis. The experiment studied effects of enzyme dosage, reaction time, sulfuric acidconcentration and acid hydrolysis time on yield of NCC. The yield of sample Ⅰ-NCC was26.2%with sulfuric acid concentration, enzyme hydrolysis time, enzyme dosage and acidhydrolysis time were respectively55%,15h,40IU and120min. Sample Ⅰ-NCC was in twoforms of rods and spherality analyzed with SEM. Rod-NCC was with length of about30-100nmand diameter of about10nm, while spherality-NCC was with diameter of about30-60nm.NCC was prepared from sample Ⅰ, sample Ⅱ and sample Ⅲ by cellulase Ⅰ pretreatmentand sulfuric acid hydrolysis. The effect of pretreatment and sulfuric acid hydrolysis conditionson the yield of NCC were researched by designing single factor experiment. Enzyme dosagewas60IU and hydrolysis time was24h were better conditions of cellulase Ⅰ pretreatment. The yield of sample Ⅰ-NCC was31.2%with the sulfuric acid concentration of59%and hydrolysistime of150min. The yield of sample Ⅱ-NCC was53.45%with the sulfuric acid concentrationof59%and hydrolysis time of150min. The yield of sample Ⅲ-NCC was66.33%with thesulfuric acid concentration of57%and hydrolysis time of150min.NCC was prepared from sample Ⅲ by cellulase Ⅱ pretreatment and sulfuric acid hydrolysis,while enzyme hydrolysis temperature and time were respectively50℃and24h, solid-liquidratio and acid hydrolysis temperature were respectively1:8and45℃. The influence of enzymedosage, sulfuric acid concentration and acid hydrolysis time on the yield of NCC was studiedby designing orthogonal experiment. The yield of sample Ⅲ-NCC was35.7%with enzymedosage of50IU, sulfuric acid concentration of57%and acid hydrolysis time of120min. SampleⅢ-NCC was in two forms of schistose and spheres analyzed with SEM. Schistose-NCC waswith length of100nm and width of15-50nm, sphere-NCC was with diameter of30-50nm.There was little effect of increasing cellulase pretreatment on the structure and crystal formof NCC, which was analyzed by FTIR and XRD. TG analysis showed that sulfuric aciddecreased particle size and increased specific surface area and active groups in the process ofdegradation. The existence of sulfuric acid groups and defect points leading to the decrease ofthermostability of NCC, while the temperature started to degrade was lower.Methanol treatment was beneficial to improving direct adhension between NCC and fibroinin the electrostatic spinning. After treatment, the tensile strength of SF membrane,1%NCC-SFmembrane,3%NCC-SF membrane and5%NCC-SF membrane were respectively increasingby39%,111%,444%and220%. In addition, methanol treatment could reduce crystallinestructure of Silk Ⅰ but increase Silk Ⅱ, in other words, it could reduce the random coil andα-helical conformation of silk fibroin but increase β-pleated sheet. The structure of silk fibroinwould be more stable and insoluble in water.