Growth and depolymerizating enzyme activity on agar cultures at two pH levels in fungi from soils of Celtis tala and Scutia buxifolia forests and Distichlis spicata grassland in the eastern Buenos Aires province (Argentina)

ELÍADES L, SAPARRAT M, CABELLO M, VOGET C.

Carlos Paz

Congreso; VI Congreso SAMIGE; 2009

The fungal degradation of polymers such as proteins, starch and cell wall-associated polysaccharides involve a battery of extracellular enzymes, whose production and properties depend upon the fungal species, strain, and culture conditions. The pH level in the medium is a key factor key in the process. There are relatively few reports on the pH effect on the growth and levels of depolymerizating enzyme activity in fungi associated with extreme environments under stressful conditions. An example of environments like this is a native xerophilic forest dominated by two tree species Celtis tala and Scutia buxifolia and its Distichlis spicata (L.) GREENE grassland associated located on the eastern part of the Buenos Aires province (Argentina). This area is characterized by diferent soil types including alkaline-calcareous, neutral and alkaline-sodic soils. These soils and their associated plants might be an isolation source for fungi with enzymes tolerant to different pH range and/or highly active at extreme pH, which might be used as biotechnological tools. The alkaline enzymes have potential applications in several industries such as in ones processing leather, food and pharmacological products. The aim of this study was to analyze the ability of several fungal strains, isolated from soils of C. tala and S. buxifolia forests and D. spicata grassland in the eastern Buenos Aires province (Argentina), to grow and produce enzymes with amylase, cellulase, protease and chitinase activities in agar cultures at pH 6.0 and 9.0. Most of the fungal strains grew better on agar cultures at pH 6.0 than ones at pH 9.0. However, Fusarium and Cylindrocarpon species showed similar growth diameters at both pH tested. All the strains tested revealed proteolytic activity on agar cultures at pH 9.0. However, amilolytic and cellulolytic activities at pH 9.0 were only detected in 12 and 10 isolates respectively. A. murorum showed high proteolytic activity as well as amilolytic one. However, any Acremonium species tested revealed cellulolytic activity under the assayed conditions. Except Aspergillus ustus, which did not present any enzyme activity tested, the other Aspergillus species showed ability for producing amilases, cellulases and proteases on agar-cultures at both pH levels. Although the most of the Fusarium species tested revealed only proteolytic activity at both pH, F. solani produced also cellulases at pH 6.0 and 9.0. Paecilomyces lilacinus and Penicillium chrysogenum presented only proteolytic activity at both pH levels. Trichoderma harzianum and T. saturnisporum showed also proteolytic activity at both pH levels. Only Acremonium murorum, Humicola grisea, Metarrhizium anisopliae, Scopulariopsis brevicaulis and Stachybotrys chartarum showed chitinase activity at pH 6.0 and 9.0.