玉米秸秆预处理后的酶水解及丁醇发酵

[目的]寻求玉米秸秆预处理后的最佳酶解工艺条件。[方法]采用碱浸泡法和氨水浸泡法对玉米秸秆进行预处理,考察预处理方法以及温度、酶用量、pH值、底物浓度等因素对玉米秸秆酶水解的影响,得出最佳酶解条件,并利用最佳条件下的水解液进行丁醇发酵。[结果]碱法预处理玉米秸秆能有效地提高酶的水解效率。玉米秸秆经过预处理后的最佳酶水解工艺条件为：pH值4．5～5．0,温度50℃,底物浓度3．33％,酶用量950U／g秸秆。利用秸秆水解液进行丁醇发酵后,溶剂（丁醇、丙酮、乙醇）的产率比值为10．O：1．5：1．0,与传统发酵（6：3：1）相比,提高了丁醇所占的比值。[结论]该研究为以木质纤维素为原料进行新能源的开发和利用验提供试验依据。     

Optimization of formic/acetic acid delignification of Miscanthus × giganteus for enzymatic hydrolysis using response surface methodology

A Box-Behnken experimental design and response surface methodology were employed to optimize the pretreatment parameters of a formic/acetic acid delignification treatment of Miscanthus × giganteus for enzymatic hydrolysis. The effects of three independent variables, namely cooking time (1, 2 and 3 h), formic acid/acetic acid/water ratio (20/60/20, 30/50/20 and 40/40/20) and temperature (80, 90 and 107 °C) on pulp yield, residual Klason lignin content, concentration of degradation products (furfural and hydroxymethylfurfural) in the black liquor, and enzymatic digestibility of the pulps were investigated. The major parameter influencing was the temperature for pulp yield, delignification degree, furfural production and enzymatic digestibility. According to the response surface analysis the optimum conditions predicted for a maximum enzymatic digestibility of the glucan (75.3%) would be obtained using a cooking time of 3 h, at 107 °C and with a formic acid/acetic acid/water ratio of 40/40/20%. Glucan digestibility was highly dependent on the delignification degree.     

发芽咖啡豆a-半乳糖苷酶的性质研究

[目的]研究发芽咖啡豆a-半乳糖苷酶的酶学性质。[方法]从发芽咖啡豆中提取a-半乳糖苷酶,研究不同温度和pH下的酶活,并确定该酶的最适温度和pH。研究了不同金属离子和不同离子强度（NaC1）对a-半乳糖苷酶酶活的影响。Lineweaver-Burk双倒数作图法测定该酶的Km和Vmu[结果]a-半乳糖苷酶的最适温度和pH分别为45℃、6．0,热稳定温度范围为20～50℃,pH稳定范围为5．0～7．0。Na^＋、K^＋、Mg^2＋和cu^2＋对a-半乳糖苷酶酶活的影响不大,zn^2＋促进酶活,Ba^2＋对酶活稍有抑制,Hg^2＋强烈抑制d．半乳糖苷酶的活性。在0～0．25mol／L离子强度（NaC1）范围内,a-半乳糖苷酶的酶活不受影响。Lineweaver—Burk双倒数作图法测定该酶的k和n。。分别为0．556mmol／L、1．19μmol／min。[结论]该研究为发芽咖啡豆a-半乳糖苷酶的进一步应用提供理论指导。     

固定化漆酶酶促合成茶黄素工艺的研究

[目的]探索固定化漆酶酶促合成茶黄素的工艺。[方法]采用D152树脂固定化漆酶体外酶促氧化茶多酚合成茶黄素。通过单因素试验研究反应温度、pH、酶浓度、反应时间和通氧量对合成茶黄素的影响,在此基础上进行茶黄素的酶促氧化合成反应,之后测定茶黄素产量。[结果]采用树脂载体D152固定化得到的固定化漆酶,在重复使用5次后,固定化漆酶催化活性约为原始催化活性的70%;在重复使用10次后,酶催化活性仍然可以保留48%左右。固定化漆酶促氧化的最佳条件为：反应温度60℃,最佳pH 5,底物浓度2.0g/L,通氧量20 L/min和反应时间1.5 h。[结论]采用树脂载体D152可有效固定漆酶。与游离漆酶氧化法相比,固定化法能有效提高漆酶的稳定性和利用效率,反应产物也更易于纯化。     

西兰苔籽中硫代葡萄糖苷酶解条件的研究及产物的鉴定

[目的]研究西兰苔籽中硫代葡萄糖苷酶解的影响因素,确定硫苷酶解的最佳条件并分析和鉴定酶解产物。[方法]以西兰苔籽粉末为材料,研究不同的温度、pH以及时间对酶水解的影响,并且利用气相色谱-质谱连用技术分析鉴定了酶解产物。[结果]酶解时间为8h,水解温度为25℃,pH值为7是最佳酶解条件。利用气象色谱-质谱连用技术分析鉴定出5种化合物,占硫苷酶解产物中挥发性化合物总量的80%。[结论]确定了西兰苔籽中硫代葡萄糖苷酶解的最佳条件,并为西兰苔籽的抗癌活性研究提供了一定的理论基础。     

淡水鱼内脏研制宠物食品的工艺研究

[目的]探索淡水鱼内脏研制宠物食品的工艺。[方法]以淡水鱼内脏为原料,比较酶解法与离心法对提取鱼内脏中蛋白质的影响,通过膨化工艺参数选择试验考察挤压温度、螺杆转速、喂料速度等因素对产品质量的影响,确定宠物（猫狗）食品最佳工艺参数。[结果]用离心法处理鱼内脏,蛋白质回收率可达85.48%,但处理后滤渣较多。用酶解法处理鱼内脏,蛋白质和脂肪等营养成分回收率高,滤渣少,酶解最佳条件是：酶解温度50℃,复合酶添加量0.6%,木瓜与风味蛋白酶比例为1∶2,料液比为1∶1.5,水解时间为2.5 h。宠物（猫狗）食品膨化工艺参数确定为：各区温度分别是Ⅰ区76℃、Ⅱ区135℃、Ⅲ区176℃,螺杆转速50 r/min,喂料速度17 r/min。[结论]淡水鱼内脏蛋白质的提取工艺,以酶解法优于直接离心法。     

碱性蛋白酶酶解丰年虫卵蛋白工艺条件优化

以丰年虫卵为原料,利用碱性蛋白酶酶解制备营养价值更高的多肽,并对其水解参数进行优化.以水解度(DH)为指标,通过单因素试验研究酶解时间、酶解温度、pH、底物质量分数及加酶量等因素对碱性蛋白酶酶解丰年虫卵蛋白质过程的影响.在此基础上利用3因素(pH、酶解温度和加酶量)中心组合试验设计,得出最优酶解时间为150 min,底...     

Evaluation of thermomechanical pretreatment for enzymatic hydrolysis of pure microcrystalline cellulose and cellulose from Brewers’ spent grain

Microcrystalline cellulose (Avicel PH102) and Brewers’ spent grain (BSG) were subjected to Détente Instantanée Contrôlée (DIC) thermomechanical pre-treatment before exposure to cellulases (Celluclast 1.5 L). In a first part, we showed that the addition of β-glucosidase (Novozym-188) increased the hydrolysis yield of Avicel. A maximal theoretical yield (100%), was obtained for 5 and 10 g/L of Avicel using a mixture of Celluclast 1.5 L/Novozym-188. After DIC pre-treatments, the initial rate and final yield of hydrolysis decreased in comparison with those from untreated microcrystalline cellulose. This phenomenon may be due to the modification of the crystallinity of pure cellulose and the formation of inhibitors during the pre-treatment. In a second part, BSG was thermomechanically pre-treated and hydrolyzed. The results showed that the hydrolysis yield of BSG treated at pressure levels between 2 and 7 bar during 15 min was strongly improved compared to hydrolysis yield of untreated BSG. The optimized hydrolysis process, under intensive DIC conditions, achieved a glucose yield corresponding to 100% of the theoretical cellulose value. The morphology of BSG samples was studied with Scanning Electronic Microscopy (SEM) and highlighted that the structure of pre-treated BSG showed an important disruption compared to the rigid structure of untreated BSG.     

Effects of flax lignin addition on enzymatic oxidation of poly(ethylene adipate) urethanes

Lignin use in polymer industry has recently become very attractive from both economical and environmental reasons. In the specific case of blending, the addition of low lignin amounts was found to improve the properties and extends the application field of other natural or synthetic polymers, but the effects of oxidative enzymes on resulting blends are widely unknown. Thereby, the current study was carried out to determine some potential effects of small flax lignin concentrations (4.2 and 9.3 wt%) on the enzymatic degradation of a poly(ethylene adipate) urethane (PU). Thin cast films of PU and its lignin blends were incubated for 3 days at 30 °C with buffered solutions of fungal peroxidase and laccase extracted from Aspergillus sp., and compared with the untreated ones. Changes in surface structure and morphology were investigated by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM), while the impact on bulk was assessed from tensile tests and thermogravimetry analysis (TGA). Although the addition of flax lignin reduces the surface structural modifications after enzyme treatment, the morphology, tensile and thermo-oxidative characteristics are still affected, with laccase showing the higher degradative efficiency. The lignin concentration, its high impact on the resulting blends morphology and relative low resistance to laccase and peroxidase degradation was the most important factors proved to driven the enzymatic oxidation.     

酶法提取啤酒糟中水溶性膳食纤维的研究

[目的]采用响应面法优化啤酒糟中水溶性膳食纤维的提取工艺,以期提高啤酒糟的综合利用价值。[方法]采用酶法提取啤酒糟中水溶性膳食纤维。在单因素试验基础上,以温度、纤维素酶量、固液比3个因素为自变量,水溶性膳食纤维得率为响应值,进行响应面分析,确定最佳工艺参数。[结果]啤酒糟中水溶性膳食纤维最佳提取条件:温度为50.8℃、纤维素酶量为6.7%、固液比(g∶m L)为1∶14。当满足最佳提取条件时,验证值为5.16%。根据最佳提取条件进行验证试验,水溶性膳食纤维的实际得率为5.09%,相对误差为1.36%。[结论]酶法提取提高了水溶性膳食纤维得率,且操作简单、可重复性强,适用于啤酒糟中水溶性膳食纤维的提取。