Difference between revisions of "Team:SDSZ China/pf"

5).Transformation

Overview

Up to this step, the purification of crystalized chitin from lobster shells is completed through the steps of the pretreatment of materials, reaction with alkali solution, rinsing and removing minerals. However, all of these steps are only preparations for the last and the most crucial step of the whole reaction system: transformation. Applying biologic method of transformation to chitosan’s industrial production demands specially designed mechanical device that controls not only the release time of engineered E. coli cells but also the complete reaction process and further purification treatments of final products.

Mechanical design

The container of the reaction is composed of three layers, with the first layer filled with LB culture, the second layer divided into four chambers, each of which filled with engineered E. coli cells and the lowest layer placed with purified chitin transported from the former reaction tanks. At the bottom of each layers are discharge openings, and four timers are implemented on the walls of the second layer to control the releasing time of cultured bacteria. An ultrasonic cell disruptor is attached to the second layer of the container and a centrifugal machine is connected with the third layer of the container. The centrifugal machine is responsible to centrifuge crude chitosan obtained from the catalyzation of enzymes and centrifuge the adherent protein from the bacteria leftover and LB culture. A container is connected to the centrifugal machine with transport device to store the purified products, and a drying unit is attached to the container to dry the products for long-time and stable storage.

The catalyzation and decomposition functions of enzymes require suitable environment and time to realize, which makes the design and control of the releasing time as well as the culture of bacteria especially crucial in the complete reaction system. We aim to be efficient, time saving and as economic as possible during the automatic process of transformation, and thus have designed the reaction tanks with the belief that the mechanical design should not only be applicable in industry, easy to operate but also energy and time saving. When LB culture is released into the middle layer of the container, timers on the tanks would begin recording and half of the bacteria in each segment of the second layer is released to the ultrasonic cell disruptor when they reach the stagnate phase of cell growth, as the most abundant protein are expressed. This can be achieved with reference to the data from previous experiments on the measurement of the curve of E. coli’s cell growth and through the control of timers on the reaction tanks. What needs to be stressed here is that the second layer of the reaction tank is divided into four segments and each segment has an individual discharge opening that allows the bacteria into the third layer. The design allows the purified chitin at the bottom level to be always reacting with enzymes since LB is released to different segments with time difference, and thus the bacteria reach the stagnant cell growth period at different moments. After the cells are completely disrupted, the enzymes that are released from the cells are transported to the lowest level of the former reaction tank to get in contact with purified chitin and start to react actively. The final products from the reaction would undergo one last step of treatment which is the further purification through centrifuge and are then abstracted and collected for storage.

1） Efficiency
Through the design of reactors and time-control systems, the efficiency of production is greatly enhanced. Through numerous experiments in the lab, we found out that there is no need to grind the lobster shells during the pretreatment process, for the reaction can take place spontaneously without the shells being grinded, and thus reducing the time needed to treat the materials aforehand.
The design of the linked reaction tanks for the removal of protein and minerals reduces the time that each compartment stays unoccupied, and thus improves the efficiency in a great deal. The traditional time for one fixed amount of materials to transform completely is seventy-two hours per unit while using our new plan, we simply need fifty-four hours per unit and increase the efficiency by 33%.

2） Energy Consumption
Since none of our designed reaction tanks are unoccupied individually for long period of time and the linked reaction tanks work as integrated systems, the consumption of energy is conspicuously decreased during the complete process.
The only step of our reaction through the processing of the machine that requires heating takes place when treating the materials with alkali. Energy usage is reduced in that only one of the three tanks needs to be heated discontinuously during the complete process of the reaction, and it only takes 2% of the total amount of time.

3） Safety
Our initial purpose of designing the machine was to solve the existing problems of industrial production, which include high level of safety risks. The redesigned flow of production greatly reduces the possibilities of occurring safety accidents in that we adopted low concentrated alkali and acid while dealing with the reactions.
Since there are no specific criteria in market on the use of acid in chitosan production, we used the exoskeleton of lobsters to experiment and found out that acid with the concentration of 5mol/L is the most effective dose in industry conversion. Though the data does not seem a grand difference, usually the concentration of hydrochloric acid in industrial production is 30%, which can cause corrosion and seriously harm human bodies while in contact.

4） Labor demand
The automatic machine requires fewer laborers during the production and thus reduces the cost for factory owners. We have noted that not grinding the shells in the first unit of the machine does not affect the efficiency of the production. As a result, we completely deleted this step which used to demand large involvement of laborers and artificial operation. What is more, all of our devices are equipped with timers, sensors or transporting devices that shape the reaction tanks together as a system, through which automatic processing is consequently achieved.

5） Waste Treatment
One of the most significant advantages of using biologic method to treat chitin is that it causes no water pollution. The only by product of enzyme catalysis is acetic acid which is dissolvable and causes trivial pollution to natural environment if released without treated.
What is more, all of the liquid waste of the reactions is collected and treated for release to the environment, being more environmentally friendly than the release of chemical concentrated solution caused by the chemical production of chitosan.