PRELIMINARY STUDIES ON THE CAPACITY OF SOME MICROORGANISMS FOR THE SYNTHESIS OF PHYTASES

Phosphorus is one of the major constituents of which are involved in metabolic processes, nucleic acid and cell membranes biosynthesis as well as in the regulation of a large number of enzymes. Phytate (myo-inositol hexakisphosphate 3-phosphorilase) is the main storage form of phosphorus in various crops (cereals, legumes, and oilseed crops) and its accumulation in natural ecosystems could reduce the availability of various metal ions such as Fe, Zn, Mg or Ca, and could cause environmental pollution effects. Phytases are enzymes that catalyze the hydrolytic phosphate cleavage of phytic acid to lour inositol phosphate esters and inorganic phosphate. In the case of monogastric animals which do not have microbial phytases in their digestive system, the formation of insoluble metal cation-phytate complexes at physiological pH values is regarded as the major reason for poor mineral availability, because these complexes are essentially nonabsorbable from the gastrointestinal tract. However, phosphorus from soil is largely unavailable due to its rapid immobilisation of the organic and inorganic soil constituents. Several studies are focused on the exogenous and endogenous microbial phytases (produced by fungi - Aspergillus niger, Aspergillus ficuum, yeasts - Saccharomyces cerevisiae, or bacteria - Leuconostoc mesenteroides, Bacillus amyloliquefaciens) and their influence in the phytic acid dephosphorylation. The identification and the characterization of new microbial strains able to produce phytase and possible other important compound continue to be of large interest both for fundamental studies and for practical applications. For this reason, the aim of the present work was the identification of new phytase producing microbial strains from soil samples of different origins and by using collection microbial strains. The phytase activity was detected by cultivation on phytase specific medium (PSM) [1.5% glucose, 0.5% (NH4)2SO4, 0.05% KCl, 0.01% MgSO4.7H2O, 0.01% NaCl, 0.01%, CaCl2.2H2O, 0.001% FeSO4, 0.001% MnSO4, pH 6.5 with 0.5% sodium phytate). Six bacteria strains (BPA, OS15, OS17, B4, B5 and B6) and one fungal strains (A.niger An) capable of hydrolyzing sodium phytate were recognized by their surrounding clear halo on PSM containing plates. Preliminary experiments on the characterization of the new isolates were also realized.