Microwave/enzyme Intervention In The Extraction And Reaction Mechanism Of Bagasse Hemicellulose

The comprehensive utilization of agricultural and forestry biomass resources has become one of the important means to solve the energy and environmental problems in the world today.The development of second natural polysaccharides hemicellulose is an important part of the comprehensive utilization of biomass resources.In order to solve the basic scientific problems,such as low yield and serious degradation in the traditional hemicellulose extraction process,in this paper the rich bagasse resources in Yunnan was used as the raw material,and the bagasse was treated by laccase to oxidize the lignin in the bagasse.Then,the physicochemical properties and fiber microstructure of the bagasse hemicellulose before and after the enzyme treatment were investigated.The mechanism of hemicellulose extraction by laccase treatment enhancing microwave/alkali method was studied.The analysis on chemical compositions of bagasse before and after laccase treatment showed that laccase treatment was beneficial to the decrease of lignin,hemicellulose and extractive content in bagasse,and the decrease rate of ash content was over 80%.Under the conditions as followed: laccase dosage 120 U/g,treatment time 5 h,solid-liquid ratio at 1:15,treatment temperature 50?,and pH 5,The lignin removal rate of raw materials in bagasse could reach 17%.The micromorphology and pore analysis of bagasse before and after laccase treatment with SEM and BET showed that the surface of bagasse after laccase treatment showed obvious cracks,even the layer fracture occurred under the dosage of 160 U/g,and the specific surface area was 90.5% more than that of bagasse without laccase.Hemicellulose extraction of bagasse treated and untreated by laccase using microwave/alkali technology was studied at sodium hydroxide concentration of 8%,extraction time of 50 min,microwave power of 800 W,extraction temperature of 90°C,and solid-liquid ratio of 1:20.The yield of hemicellulose treated with laccase was as high as 89.0% on the optimum conditions the yield of hemicellulose without laccase treatment was 20 percentage points higher.In addition,the composition of hemicellulose in the bagasse before and after laccase treatment by IC showed that the laccase treatment process had almost no effect on the composition of bagasse hemicellulose.The main components of both are mainly xylose,but only in the branch chain.The content of sugar units was slightly different,followed by arabinose,galactose and glucose,respectively.The molecular weight analysis of bagasse hemicellulose showed that the heavier molecular weight of bagasse hemicellulose after laccase treatment(7728 g/mol),the degree of dispersion is lower(1.95).The study on the extraction mechanism of bagasse microwave/alkaline hemicellulose treated and untreated by laccase showed that the microwave/alkaline methods included the main dissolution phase and residual dissolution phase.The activation energy required for the dissolution of bagasse hemicellulose was lower.The activation energies of the two stages were 14.58 kJ/mol and 19.06 kJ/mol,respectively,which were lower than the activation energy of the untreated sample by 33% and 36%,respectively.It proved that laccase pretreatment increased the dissolution rate constant of hemicellulose and the strengthening effect of microwave/alkali hemicellulose extraction.