Mode of action of a minor xylanase from Thermoascus aurantiacus on polysaccharides and model substrates

The mode of action of a minor xylanase on a variety of polysaccharides and model substrates was investigated. The enzyme was excreted by Thermoascus aurantiacus grown in solid state fermentation (SSF). The purified enzyme had a molecular mass of 33,000. Thin layer chromatography analysis showed that the endoxylanase liberated short fragments from polysaccharides. The enzyme hydrolysed aryl-β- -cellobioside and the chromogenic (fluorogenic) 4-methylumbelliferyl-β-glycosides of xylobiose (MeUmbXyl₂) and xylotriose (MeUmbXyl₃) at the agluconic linkage. The results suggested that the endoxylanase belonged to family 10.     

Enzyme activity during germination of different cereals: A review

The germination process increases enzymatic activity. However, this does not occur in the same way in all cereals. It depends on the type of enzyme, the cereal, and the conditions of germination. During germination, most enzymes are localized in the aleurone layer and the scutellum. Some of them, such as xylanases, proteases, and β-glucanases, are also localized in the endosperm while β-glucanases and lipases have been identified in the embryo. The maximum activity of the enzymes in most cereals start from day 4 of germination. Germination allows the hydrolysis of macromolecules and compounds like β-glucans and phytic acid. In cereals, starch is the component that presents the most morphological changes. Germination mobilizes and increases the activity of some enzymes. Temperature, steeping time, and variety are determining factors in the activation time. At higher temperatures, the enzymatic activation is generally faster; however, there are some exceptions. The use of germination could be a promising resource for modifying grain properties and increase enzymatic activity; also, this process is simple and economical.     

湿纺亚麻纱的生化联合处理工艺

为解决湿纺亚麻纱条干均匀度差,成纱粗硬,织造易断头等问题,探讨了一种湿纺纱的生化联合处理工艺,即先通过Na OH/尿素溶液改性,再经漆酶/酸性木聚糖酶复合处理工序,研究其对亚麻纱线性能的影响。结果表明,在Na OH/尿素溶液改性中,最优工艺参数即Na OH用量为6.5%(o.w.f),复合酶处理中漆酶用量为4.0%(o.w.f),酸性木聚糖酶用量4.5%(o.w.f),处理温度50℃,处理时间90 min下,处理后的亚麻纱较原纱条干CV值提升41%,毛效提升134%,断裂伸长率提升95.8%。改善了亚麻纱的物理机械性能,为亚麻纱的织造工序创造一定的条件。     

枯草芽孢杆菌木聚糖酶的克隆表达及其酶解两种木聚糖的产物分析

通过基因克隆方法获得枯草芽孢杆菌木聚糖酶XynA,考察经镍离子亲和柱纯化后的XynA分别在桦木木聚糖和毛榉木木聚糖中的酶解情况,利用薄层色谱法（thin layer chromatography,TLC）及基质辅助激光解吸/电离飞行时间质谱（matrix-assisted laser desorption/ ionization time-of-flight mass spectrometry,MALDI-TOF/MS）法鉴定木聚糖酶XynA的酶解产物。运用MALDI-TOF/MS分析枯草芽孢杆菌木聚糖酶XynA酶解桦木木聚糖和毛榉木木聚糖产物不同的聚合度寡糖的分布情况。结果表明：在桦木木聚糖酶解液中,产生的中性木寡糖主要为木二糖（X2）和木三糖（X3）,酸性木寡糖聚合度为4～12,并且每一个酸性木寡糖上仅连接着一个甲基葡萄糖醛酸侧链（MeG）。在毛榉木木聚糖酶解液中,产生的中性木寡糖与在桦木木聚糖酶解液中相同,酸性木寡糖的结构相似,聚合度为4～16。因此木聚糖酶XynA具有生产木二糖（X2）和木三糖（X3）以及酸性木寡糖（MeGXn）的功能。     

一株嗜热菌产耐热木聚糖酶对馒头品质和保质期的影响

研究嗜热细菌Geobacillus sp. PZH1产耐热木聚糖酶对馒头品质及保质期的影响作用。从嗜热细菌Geobacillus sp. PZH1制备木聚糖酶,添加到面粉中制作馒头,观察其对馒头品质和保质期的影响。结果表明：在馒头中添加适量的耐热木聚糖酶,能明显降低馒头的持水性,提高面筋网络的弹性,改变面团的加工及稳定性能,增大馒头体积,并能有效抑制馒头中细菌的生长,延长馒头的保质期。     

微量测定木聚糖酶活力的新方法——MBTH法

建立一种木聚糖酶活力的微量测定新方法--3-甲基-2-苯并噻唑酮腙(MBTH)法。根据木聚糖及其酶解产物的特殊性,研究MBTH法的显色条件,并以多点测定法对酶活力测定中的几个关键参数进行探讨。结果表明：蛋白质在其质量浓度低于30μg/mL时对测定无干扰;木聚糖溶液的最佳测定质量浓度为4mg/mL;较高的酶解温度会使木聚糖酶在测定过程中失活,因此,酶活力测定的最佳温度为30℃,而远低于该酶的最适温度;酶解时间为60min以内;酶解产物与MBTH试剂的反应时间应控制在13～16min之间,以15min为最佳。以酶解时间为30min计,本法检测限为0.135mU/mL,定量限为0.451mU/mL,适当延长酶解时间可相应提高酶活力检测灵敏度。该法准确度高,结果稳定,灵敏度远高于DNS法。