问题 问答题 简答题

什么叫染菌,对发酵有什么影响,对提炼有什么危害?

答案

参考答案:

染菌:发酵过程中除了生产菌以外,还有其它菌生长繁殖染菌的影响:发酵过程污染杂菌,会严重的影响生产,是发酵工业的致命伤。造成大量原材料的浪费,在经济上造成巨大损失扰乱生产秩序,破坏生产计划。遇到连续染菌,特别在找不到染菌原因往往会影响人们的情绪和生产积极性。影响产品外观及内在质量。

发酵染菌对提炼的影响:染菌发酵液中含有比正常发酵液更多的水溶性蛋白和其它杂质。采用有机溶剂萃取的提炼工艺,则极易发生乳化,很难使水相和溶剂相分离,影响进一步提纯。

采用直接用离子交换树脂的提取工艺,如链霉素、庆大霉素,染菌后大量杂菌黏附在离子交换树脂表面,或被离子交换树脂吸附,大大降低离子交换树脂的交换容量,而且有的杂菌很难用水冲洗干净,洗脱时与产物一起进入洗脱液,影响进一步提纯。

阅读理解

The Pathfinder

When we found him, he was a sorry sight. His clothes were torn, his hands bleeding. Before we reached him, we saw him fall. He lay a moment. Then he pulled himself to his feet, walked unsteadily a few yards through the woods and fell again.

After we got him out, we went back to find the gun that he had thrown down. His tracks showed that for two days he had circled in the forest, within 200 yards of the road. His senses were so dulled by fear and tiredness that he did not hear the cars going by or see the lights at night.

We found him just in time.

This man, like others before him, had simply been frightened when he knew he was lost. What had been a near disaster might have turned out as only a pleasant walk, had he made a few preparations before he stepped from the highway or off a known path.

Whatever sense of direction that a man may have, it’s still largely a question of observation. A skilled woodsman always keeps an eye on his surroundings. He notes that the shape of a mountain, the direction water flows through a swamp, and the way a tree leans across a path. With these in mind, he may be turned around many times, but he is seldom lost.

There are exceptions, of course, and once in a while a man does come across some strange problem that puts him into the “lost” situation. A rainstorm or sudden blizzard may catch him without a compass(指南针)in his pocket. Darkness may find him in a rough area, where travel is dangerous without a light.

When this happens, the normal first reaction(反应)is the fear of being laughed at as a result of his poor knowledge in the woods. He may also be concerned about the inconvenience that he will cause his friends when he doesn’t show up. This false pride may lead him to keep on the move in a false effort to find his way against all difficulties.

The person who thinks ahead is seldom in great danger. He’ll be safe if he observes carefully, thinks ahead, and remains calm.

1 The author suggested that if the man had not been found, he would have __________.

A. been shot by a gun                B. become confused

C. been attacked by wild animals        D. been in great danger

2. According to the passage, if a person gets lost in the forest, at the very beginning, he would __________.

A. worry about being laughed at  

B. push himself to find his way out

C. feel it is convenient to ask for help from his friends

D. be concerned about being frightened by wild animals

3. When a person tries to find his way in the woods, __________ is the most important 

A. intelligence  B. observation    C. direction    D. chance

4. The author tells the story of the lost man as an example of people who __________.  

A. go into the woods by themselves

B. don’t know how to signal for help properly

C. are frightened when they think they are lost

D. notice everything when stepping from the highway

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