(26f) Design of New Reactors to Produce Levan Biopolymer through Enzymatic Catalysis: Kinetics and Mass Transfer

Biopolymers are rising in importance during last years because of its potential application in biomedicine and therapeutics. Most of them are usually produced by microbial fermentation and that implies some drawbacks such as sterilization control, high-cost downstream, problems with uniformity of different parameters, etc. One of the most promising biopolymers is levan due to its amphiphilic properties. However, its production has been only focused on microorganisms and its value on market is too high so as to continue researching on its potential applications.

In this work; levan enzymatic way was explored by using the enzyme involved in the process, levansucrase from Bacillus subtilis. Levan synthesis by biocatalysis was studied and adjusted to a kinetic model which explains the behavior. Moreover, a complete analysis of reaction conditions was carried out by studying temperature, agitation speed, and pH. Furthermore, the differences between hydrolysis reaction and transfructosylation reaction were analyzed so as to a better understanding of catalytic mechanism. Results show that hydrolysis is clearly the limiting step and for that reason, the use of fructose instead of sucrose is presented as a successful alternative in order to improve yield.

Moreover, levansucrase was immobilized in two supports (a packed bead reactor and a monolithic reactor) so as to a better use and recycling of the enzyme. The effect of immobilization in production rate was also studied and a model of mass transfer through both reactors was also proposed. Mass transfer model shows not limiting transfer phenomena in external transport for both reactors, and, concerning internal transport, monolith reactor shows successful results with an effectiveness factor greater than 0.9. Additionally, the enzyme activity when it was recovered from monolith reactor was studied and it shows a low reduction in catalysis rate compared with the native one.

These results can allow reducing its high value in market and a greater implementation in biomedicine and therapeutics.