Study On The Preparation Of Antibacterial And UV-absorbing Glycosyl Materials By Enzyme-catalyzed Nonaqueous

In this paper,cellulose nanocrystals（CNCs）was used as the raw material,and SA,PABA,CA and PMCA were used as acyl donors.CNCs was catalyzed with acyl donors by immobilized lipase in the mixed solvents.The effects of time,temperature,lipase dosage and the molar ratio of acylated agents on the esterification were investigated to find the optimum conditions for the synthesis reaction.The physicochemical properties and mechanical properties of the products were characterized by modern analytical techniques such as FTIR,¹³C NMR,TGA,UV-Vis-NIR,and tensile tests.The mechanism of enzyme catalysis,the molecular structure,thermodynamic properties and optical properties of the products were studied.The composite films were prepared by the combination of E-CNCs and polyvinyl alcohol to study the mechanical and optical properties of the composite films.Meanwhile,the antibacterial activity of the E-CNCs was tested,and the physiological effects of the products on microorganisms were investigated.The optimum reaction conditions for the lipase-catalyzed E-CNCs in mixed solvents are as follows:the reaction temperature is 50℃,the reaction time is 24h,the dosage of the lipase range from 0.15g/g to 0.19g/g,and the molar ratio of the acyl donors/AGU（Anhydroglucose unit of CNCs）is 4.The FTIR results of E-CNCs showed that acyl donors had esterification with CNCs under the catalysis of lipase.The carbonyl stretching vibration peak of E-CNCs were appeared at 1733cm^-1 and 1731cm^-1.The ¹³C NMR results of E-CNCs showed that two new signal peaks are found inδ124¹36ppm andδ173¹78ppm.UVB and UVC can be completely absorbed,but the transmittance of visible light decreases by 10%-25%.When the E-CNCs content of E-CNCs/PVA composite films increase,the absorption of UVC and UVB were completely absorbed.In visible light region,the transmittance of E-CNCs/PVA films decrease by 10%-40%.The tensile strength of E-CNCs/PVA composite film is linearly correlated with E-CNCs content.When the E-CNCs content is increased to 10%,the tensile strength of E-CNCs/PVA composite film reached 49.5-50.7Mpa,the increase was 29.6%-32.7%.E-CNCs has an obvious inhibitory effect on Escherichia coli and Geotrichum candidum,and the inhibition rate to Escherichia coli was79.92%-91.36%,the inhibition rate to Geotrichum candidum was 91.78%-95.89%.In order to expand the research results,sucrose ester was prepared in this paper.The UV absorption and antibacterial properties of cinnamate sucrose ester was studied by the same method.The results of FTIR showed that the lipase promoted the acylation of sucrose with vinyl cinnamate,and the peak of the ester group was appeared in 1731cm^-1.The results of UV-Vis-IR showed that UVB and partial UVA was completely absorbed,and the transmittance of visible light is up to 90%.The antibacterial properties of cinnamate sucrose ester were determined,the inhibitory rate to Escherichia coli was 97.83%,and the inhibition rate to Geotrichum candidum reached 96.04%.Finally,the cinnamate sucrose ester the water retention rate is 76%.