Isolation, enrichment and characterization of cellulose-degrading bacteria from forest soils of Argentina

LÓPEZ, J. L.; GIUSTI, M. A.; MARTINI, C; SALAS, M, E.; LOZANO, M. J.; DEL PAPA, M.F.; PISTORIO, M.; LAGARES, A.

Mar del Plata

Congreso; VIII Congreso Argentino de Microbiología General (SAMIGE); 2012

SAMIGE

Lignocellulosic biomass has long been recognized as a potential sustainable source of mixed sugars for bioethanol production, a second generation biofuel. The key step of the process involves the use of enzymes that deconstruct lignocellulose, generically referred to as cellulases. The aim of this study was to isolate and characterize cellulose-degrading bacteria present in forest soils of Argentina, as well as test their enzymatic activity on different cellulosic substrates. Soil samples were collected from Mendoza (Valle Grande) and Neuquén (Cerro Bayo), enriched on cellulose as sole carbon source, and screened for cellulolytic bacteria by degrading halo revealed by Congo Red staining. Nine selected strains were morphologically characterized by Gram stain and identified by their 16S rDNA sequence data. All of them were further tested for their cellulase activity on different cellulosic substrates: carboxymetilcellulose (endoglucanase), Avicel (exoglucanase), xylan (hemicellulase) and filter paper (total cellulase). Isolates belonged to Phylum Proteobacteria or Firmicutes. There was a predominance of Gram positive strains, specifically of the Order Bacillales, and a number of them were isolated as bacterial consortia. All strains grew well on Avicel and filter paper enriched media, suggesting that they had the necessary enzymes to breakdown complex cellulosic substrates. However, only one strain (VG-4) showed hemicellulase activity and degradation of filter paper. Another strain (CB1-2) showed an important endoglucanase activity.Our results indicated that biomass-rich soils represent a good source of cellulolytic bacteria. Therefore, in order to improve the bioconversion of lignocellulose to bioethanol, it is important to prospect the bacterial community and provide insights into their cellulose degrading enzymatic activities.