Membrane concentration process for producing food-grade xylo-oligosaccharide from viscose fiber squeezed liquor

The invention provides a membrane concentration process for producing food-grade xylo-oligosaccharide from viscose fiber squeezed liquor. The process comprises the following specific process steps: (A) carrying out membrane concentration: firstly pre-filtering squeezed liquor for viscose fiber production, so as to remove large-granule impurities, enabling the filtrate to enter a microfiltration membrane for treatment, cyclically concentrating the permeate for 2-4 times with a nano-filtration membrane, thinning up the finally-concentrated concentrate with water, and filtrating with a ceramic membrane, so as to obtain a concentrate, namely a concentrate of squeezed alkali liquor, wherein during the 2-4 times of cyclic concentrating of the nano-filtration membrane, before every filtration, material liquid is thinned up with water and then enters the nano-filtration membrane; (B) extracting hemicellulose: adding acid to neutralize the concentrate of the squeezed alkali liquor, so as to obtain hemicellulose liquid; (C) carrying out enzymolysis: adding a compound enzyme into the hemicellulose liquid, and carrying out enzymolysis reaction, so as to obtain an enzymolysis solution; (D) purifying: filtrating the enzymolysis solution with the ceramic membrane, desalting the permeate with the nano-filtration membrane, enabling the obtained concentrate to be subjected to activated charcoal decoloring and resin ion exchange, so as to obtain a purified solution of xylo-oligosaccharide, evaporating and baking, thereby obtaining the food-grade xylo-oligosaccharide.