Optimization Of Fermentation For Production Of Oxalate Decarboxylase Of Trametes Versicolor

Oxalate decarboxylase can catalyze the decomposition of oxalic acid to formic acid and carbon dioxide. The application of the enzyme concentrated degradation of oxalate scaling in the papermaking wastewater, bio-detection of oxalic acid, and clinical diagnosis, etc. However, the current low production of oxalate decarboxylase limits the application of the enzyme. The low biomass is an important reason for the low enzyme yield. To solve this problem, the effects of shearing force of the different agitators were studied to choose the best agitator and improve the biomass yield of Tramete versicolor. Based on the above results, the induction conditions were optimized to improve the enzyme production. In the study, Jerusalem artichoke juice was also used as a carbon source to produce oxalate decarboxylase in order to improve enzyme production at a lower cost.Firstly, five different types of mixing propellers including four inclined blade propeller, double helical ribbon propeller, screw type propeller, six arrow turbine propeller and six straight blade turbine propeller were studied and their effects on biomass yield of Tramete versicolor and enzyme yield were compared. The effects of different propellers on biomass was studied at the stirring speeds of 200 r/min and 120 r/min, respectivrly. It was found that with four inclined blade propeller, the biomass yield reached the highest level of 4.1 g/L and 4.8 g/L, which was improved by 107.6% and 123.7% respectively. By using non-constant pH and constant pH inducing methods, the four inclined blade propeller still demonstrated the highest enzyme yield of 77.9 U/L and of 199.0 U/L, respectively, which was 5 times and 15.8 times higher compared with six straight blade turbine propeller.Secondly, the induction condition for enzyme production of Tramete versicolor was optimized. Four methods including batch induction, continuous induction, batch induction with constant pH and continuous batch coordinated induction were studied. To evaluate the methods, key parameters (such as biomass, protein content, enzyme activity) was measured. It was found that the volume enzyme activity and dry mass specific activity reached the highest level at 386.2 U/L and 103.8 U/g dry mass repectively by using continuous induction. By using continuous batch induction method, protein specific activity reached the highest level at 17.7 U/mg.The growth of the mycelial and the production of oxalate decarboxylase was improved by using Jerusalem artichoke juice (JAJ) as a carbon source. After fermentation, dry mycelial weight was 6.6 g/L,14.1 g/L and 17.7 g/L, respectively, by using three different sugar concentrations (20 g/L,40g/L and 80 g/L) of JAJ, aand conversion ratio of total sugar was 33%,35% and 22%, which was 4.1,4.4 and 2.8 times higher than those of glucose medium. Furthermore, different oxalic acid concentrations in JAJ medium were studied. The results showed that the highest enzyme activity reached 63.3 U/L by addition of oxlic acid to 20 mM, which was 5.1 times higher than that of glucose medium.