Study On Antibacterial Activity And Application Of Wood Vinegar

Wood vinegar is a kind of reddish-brown acidic liquid produced by pyrolysis of biomass at high temperature without oxygen.It contains dozens of organic compounds,mainly organic acids,phenols and ketones.The organic make it have excellent antioxidant and antibacterial activities,and can be applied in agriculture,animal husbandry,pharmaceutical and food industry.The developing number of antibiotic-resistant bacteria is attracting the attention.But there is no relevant research on inhibitory effect of wood vinegar on antibioticresistant strains,and the key antibacterial compounds in wood vinegar is still unclear.In addition,the active compounds in wood vinegar are easily oxidized and affected by environmental factors,it is crucial for active compounds to maintain antibacterial activity in application.Therefore,the paper identified the antibacterial compounds in wood vinegar,evaluated the inhibitory effect on antibiotic-resistant strains,and confirmed the potential and feasibility of wood vinegar as an antibacterial agent.Furthermore,the paper also proposed two new application methods of wood vinegar,which can improve the stability of wood vinegar extract and make it easier to store.It is helpful for wood vinegar to apply better and more in food and pharmaceutical industry.The active compounds in wood vinegar were identified and separated,and three fractions with different compositions were obtained.Fraction 1 mainly contained phenol and 2-methoxyphenol,the major component in fraction 2 was 2,6-dimethoxyphenol,and fraction 3 was mainly composed of 3-methyl-1,2-cyclopentanedione.The inhibitory effects of the three fractions on eight pathogenic bacteria(including one antibiotic-resistant strain)were determined by serial dilution method.The results showed that wood vinegar extract,especially phenols,had significant antibacterial activities on all tested strains.In order to further determine the antibacterial activity of phenolic compounds in each fraction,the antibacterial activity was compared between phenolic standard compounds and each fraction.The results showed that the antibacterial activity of 2,6-dimethoxylphenol was pretty different from fraction 2.By further combined antibacterial experiments,it was found that there was a synergistic antibacterial action between 2,6-dimethoxylphenol and 1,2-benzenediol.In order to improve the stability of wood vinegar extract,and make it easier to store and apply,a new method of encapsulating wood vinegar extract was proposed.The microcapsules were prepared by ionic gel method with alginate and chitosan as wall materials and wood vinegar extract as core materials.Agar diffusion test results showed that microcapsules still maintained a broad antibacterial spectrum.Besides,compared with the core material,microcapsules can make it release gradually and extend its functional life significantly.After 25 days,wood vinegar extract in microcapsules decreased only by 35.09%,while the wood vinegar extract without any protection decreased by 85.88%.In vitro simulated digestion experiments showed that microcapsules can release selectively in the digestive system.Antibacterial polymeric films were prepared with chitosan and wood vinegar.FTIR spectra showed that intramolecular and intermolecular hydrogen bonds were formed between wood vinegar and chitosan.The bonds improved the mechanical properties and reduced water vapor permeability of chitosan films.The antibacterial test results showed that wood vinegar significantly improved antibacterial activity of chitosan,adding 0.5% wood vinegar extract can reduce minimum antibacterial concentration from 62.50 ?L/m L to 15.63-31.25 ?L/m L.In addition,the film was used to preserve fresh fruits,the results showed that adding 5.0% wood vinegar extract could not only facilitate fruit preservative,but also effectively prevent gas exchange.