操作酶反应器应该注意哪些事项？
参考答案：1.保持酶反应器的操作稳定性
2.防止酶的变性失活
酶的稳定性对酶反应器的功效是很重要的。调节反应液pH\加快搅拌促使混合均匀。如果底物和产物在反应器中不够稳定的话，可以采用高浓度的酶，以减少底物和产物在反应器中的停留时间，从而减少损失。
酶反应器操作中，生产能力逐渐降低，主要原因是固定化酶活性降低或损失。造成固定化酶活性损失的原因：
（1）酶本身的失活；
（2）酶从载体上脱落；
（3）载体的破碎或溶解。
3.防止微生物污染
| A total of 4.6 million digital televisions have been sold, and the sales of HDTV sets have quadrupled since last year. Consumers have bought HDTVs to play their DVDs and to have clearer pictures and wide screens. Only a small percentage of the people who have purchased HDTVs, however, have actually hooked their TVs up to receive high-definition television digital signals. Perhaps television viewers are having trouble keeping up with the changes in technology. Even the manufacturers of HDTVs, like Mitsubishi, Thomson Multimedia, Sony, and Samsung seem to have a tough time learning how to make their sets work with the various digital TV formats because little standardization has been required or implemented in the industry. Some of the HDTVs Weigh over 200 lbs., and a variety of retailers offer a delivery service to the buyer’s home to help install the heavy sets. This is known as a white-glove service and usually comes with an extra fee. After HDTV purchasers get their sets home and hook them up, they will still need to Work to get the digital signals to their systems. Most of the industry’s cable providers do not yet offer high-definition programing, and only about 15% of commercial television stations have switched over to even the lowest improved digital pictures. Worse yet, viewers may need to install antenna before they can even get the digital signals to their new HDTV sets. Another frustration for home-theater seekers is that the current HDTV sets allow owners only to watch high-definition programs, not to record them. |
According to the passage, which of the following offers most of the HDTV programmes so far
A．Retailer delivery services.
B．Cable providers.
C．Commercial television stations.
D．HDTV set manufacturers.