Study On β-mannanase Production And Its Application For The Production Of Konjak Oligosaccharides

Mannan-oligosaccharides as one of the functional oligosaccharides not only promote the growth of bifidobacterium, but also is the on1y oligosaccharides that can protect exotic bacterium from setting down into our body according to recent investigation. And it is hopeful to be the replacement of antibiotics. This thesis got some main conclusions by doing researches of production ofβ-mannanase, the study on hydrolytic conditions of konjak glucomannan by usingβ-mannanase from Aspergillus niger E-56 and the study on refining technology of konjak oligosaccharides prepared by enzymatic hydrolyzing.Single factor method was employed to evaluate the effects of several variables on solid state fermentation in flask with the strain Aspergillus niger E-56. The optimum medium ingredients forβ-mannanase production in flask were as follows: the proportion of wheat bran to soybean flour 7.5 g:2.5 g , initial pH natural, the ratio of water to draw medium 1.5:1, konjak gum 0.4 g, KH₂PO₄ 0.024 g, CaCl₂ 0.0125 g, MgSO₄ 0.0125 g, (NH₄)₂SO₄ 0.125 g. The cultivation was carried out at 32℃for 84h. With these conditions, theβ-mannanase activity reached 42626 U/g dry medium; Based on the flask fermentation conditions,β-mannanase activity reached 33245 U/g dry medium with koji plate fermentation at 32℃for 72 h by adding water and turning koji.The hydrolytic conditions of konjak gum for producing glucomannan oligosaccharides were studied with high activityβ-mannanase from Aspergillus niger E-56. Based on single factor tests, the optimum conditions were obtained by orthogonal test. The optimum hydrolytic conditions were as follows: konjak gum solution 240 g/L (with deionized water), hydrolytic temperature 50℃,β-mannanase dosage 120 U/g konjak gum, and hydrolytic time 8 h. With these conditions, the range of average polymerization degree (DP) is 1.8～1.9 in hydrolysates.2%(v/v)yeast was added into konjak gum hydrolysates, the fermentation conditions is at 28℃for 24 h with 2.48% monosaccharides removal by TLC and HPLC method; the effects of active carbon powder, adsorption time and decolorization temperature on decolourization of crude mannooligosaccharides liquids were studied by orthogonal experiments. The results indicated that the optimum decolorization effect was obtained from the treatment conditions of 0.6% active carbon powder under conditions of decolorization temperature 50℃and adsorption time 2 h. The decolorization rate reached 65.58% and the recovery rate of total sugar was up to 90.18%. The particle activated charcoal has remarkable desmelt ability for the mannooligosaccharides liquids of konjaklike smell; ion exchange resin was used in konjak oligosaccharides liquids purification. By the treatment with 1:1 volume ratio between ion exchange resin including 001×7 Na,D201 and oligosaccharides liquids, 97.73% of the salty ions was removed, meanwhile, 90.98% of the pigment molecular was removed and the recovery of total sugar reached 88%.