Team:SYSU-China/project/manufactureapplications

New Fermentation Method

Microbial Fermentation is the most ancient biotechnology that human acquired. There are two different strategies throughout the history of fermentation. One is pure fermentation which was represented by modern chemical fermentation in western countries, and the other one is mixed fermentation which was represented by traditional seasoning fermentation in eastern countries.

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1. Application in Mixed fermentation

Mixed fermentation can produce more diverse products than pure fermentation and even some products that cannot be manufactured by pure fermentation. However, mixed culture system is much more difficult to engineer. In most cases, we can gain the suitable proportion of different bacteria only by coincidence even there`s computer monitoring.

Mixed fermentation is wildly used in China for thousands of year, whose produce include soy sauce, mature vinegar, rice wine and herbal medicine as well. Thus, it is in great need of engineering this ancient craft. But there are several problems for solving.

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Problems

a) how to keep system in a most suitable proportion is still a tough problem.

b) different kind of bacteria has different optimum growth conditions, and it seems impossible to maximize the utility of every bacteria in a unitary media.

c) how to improve the efficiency of fermentation is always asking for.

Solutions

Figure 1 Building a new fermentation tank(mixed)

By using cycle control and quorum transformation, we can monitor and control different kinds of bacteria: their densities in a mixed bacteria tank. As the protein can repress cycle replication, we can use it to save energy consumption for growth. Meanwhile, auto-activation method can simplify Induction Expression.

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2. Application in Pure fermentation

In pure fermentation industry, the most important device is fermentation tank. It contains engineering bacteria for fermenting, then we can get the products we want. There has a computer monitoring system to monitor and control the bacteria density and their living conditions, such as temperature, humidity, air pressure and so on. And this system needs to add new bacteria from a device into the fermentation tank constantly in order to maintain a equilibrium statement, we can call this device reproduction tank or incubator tank. But this traditional balance faces two significant problems.

Problems

a) The energy utilization ratio is not very high ----No matter in fermentation tank (a significant part ) or incubator tank (a very small part, scarely any sometimes ), the energy will be used both for reproduction and metabolism (the product we want and some other metabolites).

b) Products are not pure---- There are different metabolites mixed together, and the intermediate products of reproduction will exit, too. It is difficult to separate them and increase the cost of purification.

Solutions

Figure 2 Building a new fermentation tank(pure)

By using cycle control and quorum transformation, we can adjust these strains in fermentation tank, from the original mixed states to all in metabolic state ---and the needed bacteria can be constantly added from incubator tank.

A. All the energy can be used for metabolin producing. This mechanism is able to enhance the ratio of input and output, namely it can produce more needed metabolites each unit energy consumption, then energy will be saved.

B. Fermentation tank does not exist reproducing state of bacteria, so there are no breeding intermediate products. Finally we`ll have pure metabolites, so this mechanism can improve products purity and simplify separation and purification steps, then money will be saved.

Figure 3 Building a new incubator tank

C. The strains in incubator tank should keep in a lower density, so the bacteria can get a higher reproductive rate. So, and of course, all the energy can be used for reproducing,.