Preparation And Antifungal Mechanism Of Cinnamaldehyde Chitosan Emulsion For Wood Fungal Inhibitor

At present,the main wood preservatives used widely applied across the world for decades were metal containing water-borne wood preservatives or organic wood preservatives.These preservatives not only had high cost,but also had potential threat to environmental safety and human health.In order to expand environmentally friendly and low-cost wood preservatives for indoor use,cinnamaldehyde and chitosan from natural sources were used to prepare cinnamaldehyde:chitosan emulsion.The cinnamaldehyde:chitosan emulsion was used as a wood preservative and mold inhibition,and its particle size and stability were investigated.Meanwhile,the antifungal activity of cinnamaldehyde:chitosan emulsion against Aspergillus niger(V.)Tiegh.,the antifungal activity of white-rot fungi(Coriolus versicolor(L.)Quel.)and brown-rot fungi(Gloephyllum trabeum(Pers.)Murrill.),the cinnamaldehyde distribution,slow release property,laboratory decay resistance and laboratory mold resistance of treated wood were also studied.Meanwhile,this study focused on the possible antifungal mechanism of cinnamaldehyde:chitosan emulsion against Aspergillus niger(V.)Tiegh.The main conclusions of this paper were shown below:(1)The optimum preparation process wass: cinnamaldehyde chitosan can be prepared into a uniform and stable emulsion when the emulsifier content was 15%,the emulsification speed was 10000 rpm,and the stirring time was 10 min.The average particle size of cinnamaldehyde:chitosan emulsion with different concentrations of cinnamaldehyde was between 450-600 nm,and the PDI was between 0.3 and 0.5.The Schiff base reaction between cinnamaldehyde and chitosan can occur.The cinnamaldehyde chitosan schiff base can produce hydrogen bonds between the hydroxyl and wood,which can effectively fix cinnamaldehyde in wood cell wall and reduce the content and release rate of free cinnamaldehyde.(2)Different concentrations of cinnamaldehyde:chitosan emulsion showed a mold resistance performance against Aspergillus niger.When chitosan:cinnamaldehyde =1:0.5,the emulsion showed a lower mold resistance to Aspergillus niger,and the control efficacy was16.7%.When the concentration of chitosan:cinnamaldehyde was greater than 1:0.5,the emulsion showed good mold resistance against Aspergillus niger,and the control efficacy was more than 70%,when chitosan:cinnamaldehyde =1:3.0,the emulsion showed the best mold resistance against Aspergillus niger,the control efficacy reached 95.83%.(3)The cinnamaldehyde:chitosan emulsion could change the activities of some enzymes of Aspergillus Niger,and increase the activities of three cellulases of Aspergillus Niger in different degrees.Compared with the control group,the activities of Cx,C1 and BG enzymes were increased by 130%,82% and 79%,respectively.The emulsion had no obvious effect on the xylanase activity of Aspergillus Niger,cinnamaldehyde:chitosan emulsion mainly inhibits amylase activities of Aspergillus Niger,limiting the Aspergillus Niger decomposition of starch,reducing nutrient source of Aspergillus Niger,which showed the antifungal performance of Aspergillus Niger,cinnamaldehyde:chitosan with different concentration of cinnamaldehyde amylase activity was reduced by 18.5%,12.9% and 23.0%respectively than control group,11.7%,15.0%,10.1%;At the same time,cinnamaldehyde:chitosan emulsion could destroy the integrity of Aspergillus Niger cell membrane,and made the protein and nucleic acid in the cell leak to different degrees.High concentration of cinnamaldehyde:chitosan emulsion could make a large amount of nucleic acid leak,thus inhibiting the normal life activities of Aspergillus Niger.(4)Cinnamaldehyde:chitosan emulsion to white-rot fungus and brown-rot fungi showed different antifungal properties.The 3% of cinnamaldehyde:chitosan emulsion can inhibit the growth of white-rot fungi,completely to brown-rot fungi showed weaker antifungal performance,when chitosan:cinnamaldehyde concentration was higher than 1:1.5 to completely inhibit the growth of brown-rot fungi.The mass loss of the white-rot fungi control group and brown-rot fungi were 46.40% and 32.45%.The mass loss of the white-rot fungi treatment group was almost the same.When the concentration of the treated emulsion was increased to chitosan:cinnamaldehyde=1:3.0,the mass loss of the wood sample to white-rot fungi was the least,which was 29.83%.As for brown-rot fungi,the weight loss of all the cinnamaldehyde:chitosan emulsion treated groups was less than 10%.(5)The cinnamaldehyde:chitosan emulsion could change the normal life activities of Aspergillus Niger,white-rot fungi and brown-rot fungi,and destroy the morphology and structure of mycelia of fungi.Different concentrations of cinnamaldehyde:chitosan emulsion could change the cell membrane thickness,cells became permeable,cytoplasmic dissolution,mycelium fracture,distortion and other abnormal growth states of fungi,so as to inhibited the normal growth of Aspergillus Niger,white-rot fungi and brown-rot fungi.