2种方法提取阿拉伯木聚糖对馒头面团特性及品质的影响

分别采用水提法和酶提法从小麦淀粉加工废水中分离阿拉伯木聚糖(araboxylan,AX),并研究水提AX和酶提AX对小麦面团的粉质特性、流变发酵特性、糊化特性及水分分布的影响,运用扫描电镜、质构仪分析AX对馒头品质的影响。结果显示:酶提AX样品AX纯度为86.81%,较水提AX样品AX纯度高;适量添加水提AX和酶提AX均能改善面团的粉质特性,后者效果更为显著;AX使面粉的糊化作用降低;AX的添加降低了馒头的硬度、咀嚼性;酶提AX使馒头的蛋白质网络结构在挤压后仍能保持较好的完整性,而水提AX对馒头的面筋网络结构造成了一定影响,挤压后大量淀粉颗粒暴露出来;酶提AX的添加增加了面团的持气性,使馒头瓤气孔较为均匀,而水提AX使馒头瓤气孔大小不均匀,木聚糖内切酶可改善此破坏作用。因此,在小麦面粉制品中添加高纯度酶提AX可以实现多种优化目标。

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Xyn A,考察经镍离子亲和柱纯化后的Xyn A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Xyn A的酶解产物。运用MALDI-TOF/MS分析枯草芽孢杆菌木聚糖酶Xyn A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412,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（Me G）。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416。因此木聚糖酶Xyn A具有生产木二糖（X2）和木三糖（X3）以及酸性木寡糖（Me GXn）的功能。

Cloning of Endo-β-Glucanase Ⅲ and Expression in Eerevisiae Fermentum

Objective The aim was to construct bioengineering strains that could degrade the cellulosic solid waste. Method The cDNA of endo-β-glucanase III of Trichoderma vi ride AS313711 was cloned by RT-PCR method. After sequenced, this gene was constructed to expression vector pESP-2, and then the plasmid was transformed into competent cell of cerevisiae fermentum by electric shock, the transformant was then obtained. The enzyme activity of this transformant at the different temperatures and pH was measured by DNS method. Result The length of ORF of EG III was 1 257 bp, encoding 418 amino acids, while the deduced molecular weight was 44.1 × 103 kD. Conclusion The enzyme activity of EG III was the highest when it was at PH 4.9 and tempeture was of 60℃. Then the corresponding enzyme activity was about 100%.