Our goal is to increase the oxygen carrying capacity of engineering bacteria. We expect to increase the yield of engineered bacteria. If realized, the development of fermentation industry can be promoted. In order to get more information about our project and guide our project, we went to Bluepha to do research and interview. We also hope that by participating in the iGEM competition, we can have an impact on our community and the people around us. So we launched a questionnaire in the name of BJRS, and through the promotion of BJRS public name, to investigate public attitudes and understanding of genetically modified foods. A total of 675 feedbacks were received, ranging from under 12 to over 65, covering a wide range of educational qualifications and jobs. The results show that the public's understanding of GM is still inadequate, and the phenomenon of blind resistance is serious. So we carried out a lecture on Synthetic biology in Beijing Jianhua Experimental School.
Integrated Human Practices
Bluepha is a bio fermentation company. Its main products are bio plastics. In the company, we practically experienced biological plastic products, and learned the fermentation tank and fermentation process, also, interviewed the employees. The following is the interview record.
Here Are Some Q&As
Q: What is the most pressing issue in fermetation process？
A: The biggest issue is disinfection, which acounts for almost half of the excutive costs in most circumstances. Contamination of other bacteria lead to waste and disposal of entire fernetautib cylinder.
Q: What are the other pressing issues?
A: Yield of engineered strain and downstream processing.
Q: What is the current way of oxygen supply?
A: Currently we bubble sterilised air to the cylinder and use blades to stir for homogenous distribution of air.
Q: Have you ever think of other ways to increase oxygen capacity?
A: Not as I know it. The oxygen solubility in water gives a upper limit for oxygen capacity.
Q: What is the current fermetation rate?
A: It usually takes two to three days for a typical cylinder to finish fermetation. The downstream processes cost at least another two to three days.
Q: What factors affect the process?
A: The main factor is the nature of the engineered strain we chosen. Other factors include the product we desire, and the medium we use.
Q: How to select engineered strains in Bluepha?
A: Currently, we use a holamonas strain which survives in high salt level. This potentially prevents from contamination of other bacerium as they are not able to grow in such an extreme condition.
After on-the-spot visits and data consulting, the members of the group concluded that there were two main indicators for the evaluation of fermentation effect.
1. fermentation rate / fermentation cycle of bacteria
The fermentation of bacteria can be roughly divided into two processes. According to our understanding of fermentation process, the total cycle is about 48-72 hours. The first part is the growth period of bacteria, which lasts about 24-36 hours. When the bacteria grow to the plateau stage (i.e. no nutrient supply is needed for growth and development), it enters the second stage, that is, the production of the target product stage, which lasts about 24-56 hours, the production capacity of bacteria reaches the limit.
The fermentation rate of bacteria is mainly affected by dissolved oxygen. In the process of fermentation, the content of dissolved oxygen is restricted by two factors.
（1） Type of tank and fan blade
Different fermentation tanks and fan blades will affect the contact degree and mixing uniformity of bacteria with various nutrients and oxygen, and then affect the growth and production efficiency of bacteria. Therefore, suitable fermentor should be selected during fermentation.
（2） pH value
In the process of bacterial growth, respiration will produce lactic acid and other organic acids, resulting in less and less pH in the tank, fermentation efficiency gradually reduced. Therefore, it is necessary to adjust the pH value every half hour in the fermentation process to ensure that the fermentation efficiency does not decrease.
2. pour rate / recovery rate
After fermentation, the material in the tank needs to be recovered. Not all fermenters can produce a large number of target products, some even can not get the target products. Therefore, in this case, the concept of "pouring rate" has emerged, that is, the number of successful tanks as a proportion of the total number of tanks. This indicator is affected by two factors.
before fermentation, the fermentor must be sterilized once. If the disinfection is not complete, the mixed bacteria will be mixed into the tank and grow with the target strain. Some of the more viable strains will grab nutrients and oxygen, resulting in a serious decline in the survival and dry weight of the target strains.
（2） pH value
If pH value is not suitable for the growth of the target bacteria, it will also lead to a very small amount of bacteria, the rate of tank pouring is low.