PECULIARITY OF EXOINULINASE OF A NOVEL PRODUCER OF CITRIC ACID FROM INULIN.

This paper presents the results of research of biochemical and physicochemical properties of extracellular inulinase synthesized by the new citric acid producer Aspergillus niger-1 (12000). A method for the isolation of extracellular homogeneous inulinase from the culture broth has been developed. It was revealed that this exoinulinase, possessing at the same time invertase activity (I/S=1.14), showed inulolytic activity and stability in a wide range of pH (3.0-7.0) and temperature (20-50 oC). The metal ions MnCl2, NaCl, MgSO4, CoCl2 partially increase, and FeCl3, ZnSO4, AgNO3 suppress or completely inhibit the catalytic activity of exoinulinase. The molecular weight is 63 kDa which is typical for inulinases produced by the strains belonging to the genus Asprgillus. Fructose and glucose, which are the end products of enzymatic hydrolysis of inulin, indicate the exo-type action of the studied exoinulinase, as well as the possibility of its application in biotechnology for the production of various products from inulin. The revealed properties of this exoinulinase are also important for the optimization of the processes of citric acid synthesis by Aspergillus niger-1 from inulin under varying conditions of the fermentation. [ABSTRACT FROM AUTHOR]