【作者】 蒋琦霞；

【导师】 杨瑞金；

【作者基本信息】 江南大学 ， 食品科学， 2007， 硕士

【摘要】 本文研究了酶法水解爆破秸秆制备低聚木糖的工艺过程,其具体内容包括爆破秸秆酶法水解工艺和低聚木糖液脱色工艺研究,以及利用凝胶过滤和紫外光谱法对低聚木糖液中的色素脱除过程进行初步探讨。木聚糖酶水解爆破秸秆制备低聚木糖的工艺研究结果表明:当爆破秸秆与水比为1:7.5、黑曲霉木聚糖酶添加量为198U/g干基、pH6.0、53℃、酶解12h时,可获得较好的酶解效果,水解液总糖含量达到49.80mg/mL,还原糖含量达到17.03mg/mL、木聚糖水解率达到63.77%(w/w,对原料木聚糖)、木聚糖平均聚合度降至3.10;酶解产物中低聚糖主要为木二糖和木三糖,低聚木糖含量达到50.80%(w/w,对固形物)。对低聚木糖液脱色工艺研究获得以下结果:⑴酸析是一种很好的脱色方法,在pH3.0、50℃保持一段时间,脱色率可达40%;⑵在试验的九种活性炭中,AC5是一种比较适合的活性炭,其优化的脱色条件为:脱色温度80℃、pH3.0、振荡频率160r/min、活性炭添加量20%(w/w,对固形物)、底物固形物含量30%、脱色时间60min。在此优化条件下,脱色率达81.87%。⑶在试验的六种离子交换树脂中,阴离子交换树脂D301-G具有较好的脱色效果,优化的静态脱色条件为55℃、3h。⑷超滤脱色结果表明,膜截留相对分子质量为3000的超滤膜对低聚木糖的脱色有较好的脱色效果,其优化的脱色条件为进料温度40℃、压差0.05MPa、进料浓度6.8%。在此条件下脱色率达到99%以上,同时产品中的低聚木糖含量达到84.08%(w/w,对固形物)。用SuperdexTM Peptide 10/300GL柱和紫外吸收光谱法对低聚木糖液中的色素进行初步分析。结果表明,爆破秸秆水解液中的色素主要包括三种:一是相对分子质量在5000左右的黑色素,主要来自于原料;二是相对分子质量在500左右的焦糖色素和酸降解色素,主要来自于爆破预处理;三是相对分子质量在350左右的木质素,主要在酶解过程中产生的。酸析处理可以很好的去除相对分子质量在350左右的木质素;活性炭主要吸附的是相对分子质量在500左右的焦糖色素和酸降解色素,另外也会部分吸附黑色素。相对分子质量截留为3000的膜超滤主要截留的是高相对分子质量的色素和杂质。更多还原

【Abstract】 The process for producing xylo-oligosaccharides (XOS) with enzymatic hydrolysis of steam-exploded wheat straw was conceived and tested. The research work included the enzymatic hydrolysis of steam-exploded straw, colorants analysis and decoloring of the hydrolysate. The following results were obtained:Satisfactory hydrolysis was achieved at 1:7.5 of ratio of steam-exploded straw to water,196U/g (dried solids) of enzyme addition, pH 6.0,53℃,and 12h of reaction time. The amount of total sugar and reducing sugar in the hydrolysate was 49.80mg/mL and 17.03mg/mL, respectively. The average degree of polymerization of xylan decreased to 3.10, and hydrolysis rate of xylan reached 63.77% (w/w, based on the xylan in raw material). The oligosaccharides in the hydrolysate were mainly composed of xylobiose and xylotriose, and content of xylo-oligosaccharides in the hydrolysate reached 50.80% (w/w ,based on dried solids).Different decoluring measures for hydrolysate were investigated. Results showed that : Acid-Flocculation was a good method for decoloring of xylo-oligosaccharides syrups. Under conditions of pH3.0 and 50℃, the color stripping rate was 40%;Among the test 9 types of activated carbons, activated carbon AC5 performed best. Under conditions of 80℃, pH3.0, 160r/min, 20% of activated carbon addition(based on dried solids), 30% dried solid,60min of reaction time, the color stripping rate was 81.87%; Among the test 6 types of anion exchange resins, anion exchange resin D301-G performed best. The optimum of static decolorizing was 55℃,3h; And the ultrafiltration with a membrane (molecular weight cut-off 3000) was studied. Results showed that ultrafiltration membrane performed best under conditions of 40℃, 0.05Mpa, 6.8% dried solid, and the color stripping rate was 99% . And content of xylo-oligosaccharides in the hydrolysate reached 84.08% (w/w, based on dried solids).The colorants removement through the XOS process was investigated, using Sephadex gel permeation chromatography and ultraviolet spectra. Results showed that: SuperdexTM Peptide 10/300GL was suitable. The colorants in XOS could be mainly divided into three main species presented as follows. One was the melanin with MW5000. The second were the caramel and acid decomposition of xylose or xylo-oligosaccharides (about MW500). The third was the lignin (about MW350). Acid-Flocculation was able to remove low molecular colorants (about MW350). Activated carbon was able to adsorb caramel and acid decomposition (about MW500). Ultrafiltration membrane (molecular weight cut-off 3000) was able to remove high molecular colorants.更多还原