PROIMI   05436
PLANTA PILOTO DE PROCESOS INDUSTRIALES MICROBIOLOGICOS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
FIRST INSIGHTS INTO THE EPS-PRODUCTION ABILITY OF NATIVE ENTOMOPATHOGENIC FUNGI
Autor/es:
MARIANA E. DANILOVICH; ALEJANDRA L. VALDEZ; AGUILERA SAMMARITANO J.; VAZQUEZ F.; LECHNER B. ; JULIA I. FARIÑA; OSVALDO D. DELGADO
Reunión:
Workshop; II Workshop Polímeros Biodegradables y Biocompuestos III Workshop of the project BIOPURFIL, Bio-based Polyurethane Composites with Natural Fillers; 2015
Resumen:
Microbial exopolysaccharides (EPS)s have a variety of beneficial functions such as gel formation, absorption, cohesion, emulsification, and film formation. Different types of EPSs have been examined up to date considering their potential use in medicine as immuno-stimulators or anti-tumour agents, and as additives in cosmetics, foods and other industrial procedures . On the other hand, in pathogenic fungi, EPSs can participate in the infection mechanism. Synthesis of EPS by fungi can be affected by different factors such as culture medium composition, agitation, aeration and further operative conditions. The aim of this work was to assess the ability of five entomopathogenic fungi isolated from nature to produce EPSs when cultured in three different media, and to evaluate two different precipitating agents for EPS recovery. Five entomopathogenic fungi isolated in Argentina: Metharhiziumsp. isolates 381, 388, 409 and 413 (from San Juan), and Lecanicilliumsp. LY 72.14 (from Tucumán) were evaluated. Isolates were grown in CZM agar (7 days at 25°C) and then transferred to fresh culture medium by cutting out 5 mycelium-covered agar plugs. For EPS production, cultures were grown in 250-mL Erlenmeyer flasks containing 50 mL of three different liquid media: PMP modified supplemented with 4 g/L sucrose and 1 g/L corn steep liquor, MLP ((NH4)2SO4, 5g/L; glucose, 39 g/L) and MOPT (sucrose, 150 g/L; sodium nitrate, 2,25 g/L). The EPS production was tested after 7 days of cultivation at 25°C and 200 rpm. To recover the EPSs, culture broths were centrifuged (9000 g, 20 min) and the resulting supernatant was mixed with 2 volumes of either ethanol 96° + 1 g/L CaCl2 , or isopropanol. Biomass and EPS were measured as dry weight. Residual sugars were determined by the 3,5-dinitro salicylic acid reaction .Most of the isolates showed greater mycelial growth in MOPT medium, reaching values from 11.25 to 15.47 g/L. For the majority of isolates, EPS production was higher in MOPT. Remarkably, for Metharhiziumsp. 413, EPS production reached a value of 7.30 g/L. This result suggested that osmotic stress associated to MOPT medium may stimulate EPS production by this fungus, as also found for other recognized EPS-producing fungi [2]. The EPS recovery process was more efficient with CaCl2-amended ethanol, leading to higher EPS amounts in comparison to the isopropanol precipitation. For example, in the case of the EPS produced by Metharhiziumsp. 388, the recovery by CaCl2-ethanol precipitation allowed to achieve 4.4 g EPS/L while isopropanol-based recovery led to a lower EPS amount (2.3 g/L). This differential behavior in the presence of different precipitating agents could suggest the polyelectrolytic character of the precipitated polysaccharide, as previously described by García-Ochoa et al. for xanthan precipitation. Concerning sugar uptake, residual sugars were in some cases lower than expected, suggesting their consumption for cellular functions other than those exclusively related to EPS production.