问题 问答题 简答题

如何根据发酵过程中pH变化进行中间补料。(中间补料与pH调节之间的关系)。

答案

参考答案:

(1)补充有机氮源:添加某些具有调节生长代谢的有机氮源,如尿素、酵母粉、蛋白胨、玉米浆,保持菌的活性,补充产物合成所需的氮源。在谷氨酸生产中,尿素作为氮源时首先被菌体的脲酶分解变成氨,使pH上升。氨被利用后,使pH下降

(2)补充无机氮源:通氨、补硫酸铵

阅读理解

阅读理解。

     Danny was just tired about the way things were going. His mum came to school and talked on and on about Rick Jackson. It seemed that she would never stop talking. "Somebody's got to stop that boy!" she was shouting. " Rick's troubling everybody in the neighborhood. And he loves to pick on little boys like Danny. "

     Mrs Green, Danny's teacher, was concerned a lot. "I didn't know that Danny was being picked on," she said. " He's never said anything about this to me ! "Mrs Green looked at Danny. "How long had this been going on?" she asked. Danny could only shake his head and look at the floor. He knew if he said a word about this, he would have trouble at school.

     Danny hadn't said anything about the problem because he wanted to do things with the boys in the neighborhood. After all, most of them were nice to him. He hated to leave the gang just because of Rick. Maybe the time had come to find new friends. He felt it hard to make up his mind.

1. We learn_____ from the reading that.

A. Danny was not a good student

B. Danny's mother talked too much about the school

C. Danny's teacher knew something about Danny's problem before

D. Danny wanted to get away from Rick

2. When Danny's mother came for Mrs Green,the matter was nowto Mrs Green?

A. serious

B. common

C. untrue

D. similar

3. Danny now____.

A. was tired of the school and his friends

B. had no friends at all

C. was not sure what he would do with the problem

D. made some new friends in the neighborhood

4. Danny didn't say anything about the matter to Mrs Green because?  

A. she had known it

B. the other boys would tell her

C. he didn't want to be in trouble

D. his mother didn't want him to say it

5. The word " gang" in the reading means" _____".

A. a place for boys to play games

B. a group of young people

C. a school bus for children to and from school    

D. the teacher's office

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