Abstract

Monitoring of the evolution of the microbiological flora Ã?Â?Ã?Â?Ã?Â?Ã?Â?treated strawÃ?Â?Ã?Â?Ã?Â?Ã?Â?

Author(s): Y.Chbab, A.Echchelh, M.Aouane, A.Chaouch, M.Jadal, M.Ouhssine

The use of urea for the treatment of the straw constitutes an interesting alternative, particularly in developing countries. Its effectiveness depends, on one hand, on the intensity of the ureolysis and, on the other hand, on the effects of the ammonia produced on the composition of the straw and on the existent microbiological flora. The aim of this work is to study the effect of ammonia coming from urealyticum activity on the evolution of FMAT, total and fecal coliforms, fungus, yeasts and lactic bacterias. And this through two essays (straw+ urea alone (U) and straw+ ureamolasses). The essays were done in conditions of humidity varying between 60 % and 70 %, during 30 days and at a temperature of 20 and 22°C. Acquired results are confronted to a blank (straw + water). As a result, the medium value of the pHis 9.2 for all essays treated by urea alone (U). It is 8.5 for the essaywithmolasses. The pHof thewitnesswas only 5.5. FMAT is abundant in the witness. It reaches high levels (1.7.107 ufc/g) against 6.102 ufc/g for the essay with molasses. The lactic microbes were present in the essay withmolasseswith an abundance of 2.1.101 ufc/g. Theyweremore abundant in the witness (1.7.104 ufc/g). The same thingwas observed with yeasts. In fact, at the level of the mix straw + urea + molasses, the average of the population of yeast is 4.9.101 ufc/g. In the witness it reaches 4.104 ufc/g. These results can be explained by the influence of the high pH values in the essays with urea. The pH acts on the bacterial metabolism in general and on the ureolytic activity (hydrolysis of urea) particularly. The pH and/ or the high concentration of ammonia formed can explain the statements stopped at the level of the growth of the studied microbiological floras.