Team:Brasil-USP/Project/Reactor

Project

Bioreactors and Reactor


texto

As said previously, we intend to implement our process in scaled up bioreactors. The whole process would be divided in 3 stages, as proposed in figure 1.

Figure 1- Scheme of the whole process for the rubber degradation showing the 3 foreseen bioreactors.

The first 2 bioreactors are supposed to contain microorganisms while the last one is a chemical reactor, commonly found in polymeric industry.

Bioreactor 1 - Devulcanization

The process that takes place in this first bioreactor is the devulcanization of tire particulates. Tires are vulcanized, a process required to confer hardness and resistance to natural rubber forming sulfur bonds, that cross-link the polyisoprene chains of the natural rubber. This process allows tires to be used in the tire manufacturing procedure but, at the same time, makes it more difficult for the tire to be reused/recycled, turning the devulcanization into a very important step in our project, even if at this moment we are not genetically engineering it but only optimizing its cultivation in rubber presence.
This bioreactor will contain a special strain of Acidithiobacillus ferrooxidans, which were kindly provided by Professor Denise Bevilaqua, from UNESP (Estadual University of São Paulo). This microorganism is a wild bacteria that has the gene for tetrathionate hydrolase (TetH), which is able to reduce inorganic sulfur compounds [1]. TetH has its maximal activity in a pH range from 3 to 4, adding to that, the bacterial ideal growth is in pH 4, what let us think that the ideal bioreactor pH would be 4 [1]. Though Professor Denise Bevilaqua, who provided us the Acidithiobacillus ferrooxidans strain, recommends that this bacteria should be cultivated at 30°C, while TetH has its best activity at 25°C [2]. To achieve the best relation between bacterial growth and tire devulcanization some tests with different temperatures and pHs should be performed. The ideal stirring in cultivation is 150 rpm, to scale up maybe the rotation will also change.
Acidithiobacillus ferrooxidans is being maintained in a simple culture medium that Professor Denise Bevilaqua provided us; its composition is as follows (g/L): (NH4)2SO4 0,5; MgSO4.7H2O 0,5; K2HPO4 0,5 and FeSO4 33,3. To activate the microorganism sulfur metabolism, it is necessary to use a different culture medium with sulfur instead of iron (g/L): (NH4)2SO4 0,5; MgSO4.7H2O 0,5; K2HPO4 0,5 and S 10. This medium composition were also informed by Professor Denise Bevilaqua. Once the sulfur metabolism is activated, the bacteria can be incubated with the tire scrapes or powder, in order to initiate the devulcanization process as shown in Figure 2. The medium required for this process is very similar (g/L): (NH4)2SO4 1,5; MgSO4.7H2O 0,5; K2HPO4 0,05; Ca(NO3)2 0,01; KCl 0,05 and FeSO4.7H2O 4,43.

coloque texto aqui

Figure 1-

...........

Figure 2-

.....


3- Schematic representation of BBa_K1819003 insert


Bioreactor 2 - Degradation

texto aqui

Figure N-


texto

Chemical Reactor

texto

Figure N -


References

references

Back to top