Research On Preparation And Properties Of Antibacterial Composites Based On Licorice Residues Cellulose

Cellulose materials exhibit good adsorption,moisture retention,and gas permeability,which are beneficial to cell adhesion and growth and thus contribute to wound healing.However,the low bioactivity and non-antibacterial properties of cellulose limit its application in medical external materials.In this study,cellulose-based antibacterial composite materials of licorice residues were prepared from licorice residues to explore its application prospects in medical external materials.In this study,licorice residues were used as raw materials.Firstly,the effect of alkali dosage on the cooking effect of soda-anthraquinone(AQ)pulping of licorice residues was investigated,and the obtained licorice residues soda-AQ pulp was bleached,and the optimum alkali dosage was 18%.The bleached licorice residues soda-AQ pulp(BLSP)with the brightness of 77.8%ISO and the bleaching yield of 69.3%was obtained by peroxyacetic acid bleaching.Secondly,the enzymatic pretreatment cellulose nanofibril(ETCNF)was prepared by the combination of enzymatic treatment and homogenization.The effects of enzymtic pretreatment conditions on the performance of ETCNF were investigated.The results showed that the prepared ETCNF exhibited desirable nanofibrillar structure and high colloidal stability,and the diameter of ETCNF could be decreased effectively with prolonging enzymatic hydrolysis time or increasing enzyme dosage.Compared with TEMPO-oxidation cellulose nanofibril(TOCNF)prepared by TEMPO/NaBr/NaCIO systems and homogenization,ETCNF showed higher crystallinity index and thermal stability.Then,the composite films were prepared and characterized as follows:(1)chitosan nanofibril(CHN)and lignin nanoparticles(LNPs)were prepared by using TEMPO/NaBr/NaCIO system oxidation combined with high pressure homogenization,and anti-solvent precipitation method,respectively.The results showed that the average diameters of CHN and LNPs were 204 nm and 120 nm,respectively;the specific surface area of CHN was 15.3 m2/m3;LNPs exhibited good colloidal stability.The thermal stability of CHN and LNPs were slightly lower than that of chitosan and alkali lignin,respectively;(2)the antibacterial activity,optical properties and mechanical properties of the composite films of ETCNF@CHN and ETCNF@LNPs were compared.The results showed that the antibacterial effects of ETCNF@CHN composite films on Escherichia coli was much better than that of ETCNF@LNPs composite films.The antibacterial effects of ETCNF@LNPs composite films on Staphylococcus aureus was much better than that of ETCNF@CHN composite films.However,compared with ETCNF@LNPs composite films-ETCNF@CHN composite films had higher light transmittance(80.8%vs 73.8%)and tensile strength(32.2 MPa vs 13.5 MPa);(3)the effect of different content of CHN on the properties of ETCNF@CHN composite films were further investigated.The results showed that the antibacterial activity of the composite films increased with the increase of CHN content,especially for Escherichia coli.The hydrophobicity of the composite films were increased.The light transmittance,crystallinity,and thermal stability of the composite films were reduced.The tensile strength increased first and then decreased.When the content of CHN was 10%,the water contact angle at 3 s,the light transmittance at 750 nm,the crystallinity index,tensile strength of composite films were-40°,72.0%,78.9%,39.6 MPa,respectively.