Phytate degradation by micro-organisms in synthetic media and pea flour

Aims: To screen micro-organisms for the ability to produce phytase enzyme(s) and to use promising strains for the fermentation of pea flour. Methods and Results: Two methods using the indirect estimation of phytate degradation were evaluated and both shown to be inadequate. A third method, measuring the inositol phosphate (IP3 -IP6 ) content directly during fermentation, was used instead of the indirect estimations of phytate degradation. In synthetic media, some strains required customized conditions, with no accessible phosphorus sources other than phytate, to express phytase activity. The repression of phytase synthesis by inorganic phosphorus was not detected during fermentation with pea flour as substrate and seemed to be less significant with a higher composition complexity of the substrate. None of the tested lactic acid bacteria strains showed phytase activity. Conclusions: The methodology for the phytase screening procedure was shown to be critical. Some of the screening methods and media used in previous publications were found to be inadequate. Significance and Impact of the Study: This paper highlights the pitfalls and difficulties in the evaluation of phytase production by micro-organisms. The study is of great importance for future studies in this area.