Corrosion Resistance of Heat-Treated NST 37-2 Steel in Hydrochloric Acid Solution

Corrosion of metal components constitutes a major challenge in many engineering systems, with appropriate design, proper material selection, and heat treatment as commonly used control strategies. In this study, the corrosion behaviour of heat-treated (annealed, normalised, hardened, and tempered) NST 37-2 steel in three concentrations (1.0, 1.5 and 2.0 M) of hydrochloric acid solution was investigated using weight loss and electrode-potential methods. Results showed that corrosion rate increased with increase in acid concentration. The decreasing order of corrosion resistance was Tempered > Annealed > Normalised > Hardened > Untreated. The surface pictures of the heat-treated and untreated samples showed uniform and pitting corrosion with the latter becoming more pronounced as concentration increased.

耐酸耐高温α-淀粉酶的研究进展

介绍了耐酸耐高温α-淀粉酶在工业生产中具有经济、节能、方便操作等优势;并且概述了耐酸耐高温α-淀粉酶的菌种来源,其中耐酸性α-淀粉酶的菌种主要来源于芽孢杆菌、曲霉以及嗜热真菌;耐高温α-淀粉酶的菌种主要来源于凝结芽孢杆菌、枯草芽孢杆菌、嗜热芽孢杆菌、地衣芽孢杆菌和嗜热网络球杆菌等;本文还对耐酸耐高温α-淀粉酶的菌种选育技术方法包括物理方法、化学方法以及基因操作技术等进行了阐述。研究发现对耐酸耐高温α-淀粉酶的发酵工艺进行优化后,最高可以使酶活提高2.1倍;同时在对该淀粉酶的钙离子依赖性进行研究中,得出某些耐酸耐高温α-淀粉酶具有不依赖Ca2+的特性;最后预测人们将会运用基因工程等技术手段,不断地开发出各种特性的耐酸耐高温性α-淀粉酶。

耐酸耐高温α-淀粉酶及其菌种选育研究进展

耐酸耐高温α-淀粉酶能在高温与低p H下水解淀粉,是重要的新型工业酶制剂。概述了耐酸耐高温α-淀粉酶的热稳定性、p H稳定性及金属离子对其的影响,阐述了产酶菌种的主要来源现状,并重点对耐酸耐高温α-淀粉酶诱变育种的复合诱变、基因工程定点突变等菌种选育和古菌的相关研究进行了综述。

枯草芽孢杆菌发酵产耐酸耐高温α-淀粉酶培养基优化

耐酸耐高温α-淀粉酶具有耐酸和耐高温的双重特性,可以进一步提高淀粉糖和相关行业生产效率、降低成本,近来其研究和应用受到广泛重视。采用单因素和正交试验对枯草芽孢杆菌液体发酵产酶的培养基组分进行优化,包含碳源、氮源、金属离子和产酶促进剂等。经过优化后的主要培养基组成为:麦芽糖10%、玉米淀粉2%;胰蛋白胨1%、尿素2%;0.4%的硫酸锰;0.1%的吐温80。经优化后的耐酸耐高温酶α-淀粉酶酶活由43.13 U/m L提高到了89.15 U/m L,发酵酶活提高了一倍左右。