A multipotential hydrolytic reactor using the yeast strainKluyveromyces marxianus

In previous publications, we described the continuous production of D-fructose from enzymatic hydrolysis of inulin with immobilized permeabiliized cells ofKluyveromyces marxianus and the increase of productivity obtained by using a mutant selected by NTG action on the wild-type strain. By improving reactor performance, it has been possible to reach 2000 g/L/d of liberated sugar from an inulin solution with the mutant strain.

In addition, it has been shown that the KF 28 mutant was an invertase and pectinase hyperproducer. These enzymatic activities are also secreted by the speciesKluyveromyces marxianus. Therefore, we investigated the possibility of using immobilized cells of this yeast as a multipotential hydrolysis reactor. A sucrose hydrolysis reactor and a pectin hydrolysis reactor were set up. It is shown here that the majority of the optimized parameters from the inulin hydrolysis reactor can be transported directly to the other reactors. However, some parameters have to be adapted, especially for pectin hydrolysis.

     

Improvement of inulin hydrolysis yeast cell reactor by mutants selection

In a previous publication, we described a continuous production ofd-fructose from enzymatic hydrolysis of inulin with immobilized permeabilized cells (1).Kluyveromyces fragilis ATCC 12424 have been shown to possess inulase activity. The half life of the reactor was at least 1300 h, but productivity was relatively low (around 40 g/L/day). A selection of 50 mutants was tested on liquid medium for a possible increase of productivity. In relation to the improvement of the reactor, the most important factor is intracellular inulase activity, and this activity was increased with the KF 28 mutant. Productivity reached 2000 g/L/day with the increase (of the productivity), proportional to the increase of intracellular inulase activity.