Induction Of Oxalate Decarboxylase From Trametes Versicolor

Oxalate decarboxylase (OxDC) is a kind of Mn-containing enzyme, which is widely distributed in wood rot fungi. A few other fungi and bacteria also can produce the enzyme. Currently, more than ten oxalate decarboxylases from different sources have already been isolated and purified. Oxalate decarboxylases were successfully applied in several areas, such as enzymatic degradation of oxalic acid in the pulp and paper industry and food industry, as well as biological analysis of oxalic acid, etc. Because of the low production and lower extraction efficiency of this enzyme, the production cost of OxDC is much higher, thus limiting the enzyme applications. Inducible expression of oxalate decarboxylase is determined by some special amino acid sequences, but the specific regulatory mechanism is still unknown. In order to study the induction of OxDC in detail, to improve yields and to reduce the cost of OxDC, it is first time to study the production of OxDC by acid induction, to discuss the mechanism of OxDC induction and to optimize the extracting conditions of OxDC in this paper.Firstly, the production of OxDC from T. versicolor was studied. The aspect of research is mainly focused on inducing factors including inorganic acids (hydrochloric acid, sulfuric acid and phosphoric acid), organic acids (oxalic acid, acetic acid and citric acid) and organic salts (oxalate, acetate and citrate). The results showed that all inorganic acids could induce OxDC expression obviously. The highest specific activity against dry mycelia weight was 10.00 U/g and the highest specific activity against protein was 3.20 U/mg when sulfuric acid was used. The total OxDC activity induced by oxalic acid reached highest at the first two days and then decreased quickly at the following days, the highest specific activity against dry mycelia weight was 6.70 U/g and the highest specific activity against protein was 1.00 U/mg. The OxDC activity induced by citric acid rose continuously in later growing stage. OxDC activity after addition of acetic acid was not detected. OxDC activity was also induced by acetate obviously, the highest specific activity against dry mycelia weight was 1.77 U/g and the highest specific activity against protein was 0.23 U/mg. After comprehensive comparison of the yields of OxDC obtained by using different inducing factors, the results showed the yields of OxDC induced by inorganic acids were more higher than by other inducers, the highest volume activities of OxDC were all higher than 20.0 U/L, the productivities of OxDC were all more than 2.5 U/(L·d), and the highest specific activity against dry mycelia weight were all higher than 9.5 U/g. The possible induction mechanism behind inorganic acids and citric acid is low-pH induction, while the possible mechanism behind oxalic acid is substrate-induced and the induction mechanism of acetic acid is substrate analogue-induced.Extracting conditions of OxDC were optimized. More OxDC activity was obtained by using theTween-80-added extracting solutions. When pH value of the extraction buffer was 3.0, the highest extraction percent was gained.