Isolation of Paenibacillus sp. and Variovorax sp. strains from decaying woods and characterization of their potential for cellulose deconstruction

Abstract

Prospection of cellulose-degrading bacteria in natural environments allows the identification of novel cellulases<br />and hemicellulases that could be useful in second-generation bioethanol production. In this work, cellulolytic<br />bacteria were isolated from decaying native forest soils by enrichment on cellulose as sole carbon source. There<br />was a predominance of Gram positive isolates that belonged to the phyla Proteobacteria and Firmicutes. Many<br />primary isolates with cellulolytic activity were not pure cultures. From these consortia, isolation of pure constituents<br />was attempted in order to test the hypothesis whether microbial consortia are needed for full degradation of<br />complex substrates. Two isolates, CB1-2-A-5 and VG-4-A-2, were obtained as the pure constituents of CB1-2 and<br />VG-4 consortia, respectively. Based on 16S RNA sequence, they could be classified as Variovorax paradoxus and<br />Paenibacillus alvei. Noteworthy, only VG-4 consortium showed measurable xylan degrading capacity and signs of<br />filter paper degradation. However, no xylan or filter paper degrading capacities were observed for the pure cultures<br />isolated from it, suggesting that other members of this consortium were necessary for these hydrolyzing activities.<br />Our results indicated that Paenibacillus sp. and Variovorax sp. as well as VG-4 consortium, might be a useful source<br />of hydrolytic enzymes. Moreover, although Variovorax sp. had been previously identified in metagenomic studies<br />of cellulolytic communities, this is the first report on the isolation and characterization of this microorganism as a<br />cellulolytic genus.