Bio-degumming Of Flax Based On Solid-state Fermentation Method

The bast fiber is a biomass fiber of sustainable origin.Degumming is the primary process for extracting bast fiber.Bio-degumming is a green and low carbon method compared to chemical degumming.However,liquid fermentation-based bio-degumming generates large amounts of waste water and there is still the problem of large amounts of effluent to be disposed of.In order to explore a new pathway for green preparation of biomass fiber,this study constructed a low-carbon and water-saving progressive bio-degumming（SPB）method based on solid-state fermentation method.The effect of clean pretreatment based on physical action on breaking the biomass recalcitrance of flax fiber was investigated.On this basis,a water-saving solid-state fermentation bio-degumming method was constructed,and the effect of composite degumming by alkaline degumming flora and bio-oxidative degumming enhanced by a white rot fungus-mediator system were investigated respectively.Finally,a multi-factor network model was developed to complement the analysis of the non-liquid environmental bio-degumming process.（1）In order to break the biomass recalcitrance of flax fiber and improve the biocatalytic efficiency of the solid-state fermentation process,three physical methods were used to treat flax fiber,including cryogenic pretreatment,ultrasonic pretreatment and supercritical CO₂ pretreatment.The results show that,among the three pretreatment methods,cryogenic pretreatment is the most effective,the fiber strength is the highest after this method,the outer layer of the fiber is significantly reduced,the micro-pores on the fiber surface are significantly increased,providing more attachment sites for enzymes,and the method is simple and low cost.（2）Based on deep-cooling pretreatment to break the flax resistance barrier,a progressive bio-degumming method was developed using a complex of alkali-tolerant degumming bacteria selected by microbial evolutionary engineering under solid-state fermentation conditions,leaving only 8%of flax residual gum after degumming.Compared to traditional chemical methods,the progressive solid-state fermentation bio-degumming resulted in higher molecular weight and higher tensile strength fiber,and more importantly,saved 55%of water and 90%of chemical usage.（3）In order to improve the efficiency of solid fermentation bio-degumming,a bio-oxidation mechanism was introduced using white rot fungus as a biocatalyst for solid-state fermentation degumming,and the enhanced effect of electron mediators on bio-oxidative degumming was explored.It was found that the electron mediator enhanced the bio-oxidative degumming effect during the degumming process,aided the uniform distribution of white rot mycelium on the flax surface and resulted in more uniform gum removal.（4）A multi-factor network model was constructed based on an artificial neural network model,in order to analyse the action process of solid-state fermentation bio-degumming.The model was found to be able to establish the link between multiple influencing factors and fiber properties,and the analysis of the model revealed that pretreatment significantly improved the uniformity of fiber properties after degumming,alkaline degumming bacteria were more adaptable to the environment,and the white rot fungus-mediated oxidative degumming system was more efficient in degumming.