Acidic pH-Shock Induces the Production of an Exopolysaccharide by the Fungus Mucor rouxii: Utilization of Beet-Molasses

Depending on specific environmental conditions, microorganisms can produce exopolysaccharides (EPSs) of particular composition and physiochemical properties, and this promotes the survival of microbial populations. An extracellular exopolysaccharide (EPS), synthesized by the fungus Mucor rouxii, was found to play an important role for the protection of cells against abiotic stress such as extreme pH values or elevated temperature. This EPS was produced during 48 hr of growth, at pH 3.5 and 28 o C using beet-molasses as a low-cost substrate. The chemical composition of beet-molasses includes high concentrations of K + , Na + , Fe 2+ , and Zn 2+ which could be additional stress factors trigger the formation of the EPS. The molecular weight of the EPS was found to be 1.78 x 10 6 Da, and it had good flocculating activity for precipitation and aggregation of soil and charcoal particles. The main backbone of this EPS is a polysaccharide. The infrared spectra analysis showed the presence of urinate, hydroxyl, and carboxyl groups which are the important factors for the flocculating activity of a bioflocculant. This work is focused on studying the response of the fungus M. rouxii to produce an EPS under abiotic stress condition. An acidic pH-shock was found to be the strongest stressor for synthesizing the EPS, which showed flocculating activity of approximately 99%, exploiting beet- molasses as inexpensive carbon source. The produced EPS showed good flocculating activity, higher stability against enzymatic degradation, capability for metal removing, and is heat- stable. It may find possible applications in the industrial fields and in biotechnological processes. (Shadia M. Abdel-Aziz, Hoda A. Hamed, Foukia E. Mouafi and Amber S. Gad Acidic pH-Shock Induces the Production of an Exopolysaccharide by the Fungus Mucor rouxii: Utilization of Beet-Molasses. New York Science Journal 2012;5(2):52-61). (ISSN: 1554-0200). http://www.sciencepub.net/newyork . 9