Identification and biotechnological potential of cellulases-producing rhizobacteria from the Amazon rhizosphere

The Amazon rainforest hosts an extraordinary microbial diversity with significant yet underexplored biotechnological potential. This study aimed to identify and evaluate the production of endoglucanase, β-glucosidases and CMCase rhizobacteria isolated from the rhizosphere of Pueraria phaseoloides and Inga edulis, focusing on strains with potential applications in lignocellulosic biomass conversion. A total of 50 rhizobacterial isolates were reactivated and screened for cellulolytic activity using carboxymethylcellulose (CMC) agar. Thirty-one isolates (62%) formed hydrolysis halos, and 22 strains exhibited an enzymatic index (EI) ≥ 2.0, indicating high cellulolytic potential. Statistical analysis revealed significant differences between host plants, with isolates from P. phaseoloides showing higher average EI values than those from I. edulis. Molecular identification of the most active isolates (EI ≥ 2.0) revealed strains belonging to the genus Bacillus, including Bacillus subtilis and Bacillus velezensis. The strain B. subtilis INPA R-583, which showed the highest EI, was selected for enzymatic characterization. Kinetic analyses demonstrated stable and high endoglucanase (CMCase) activity, increasing β-glucosidase activity at later cultivation stages, and relatively low total cellulase (FPase) activity. These results indicate a functional but incomplete cellulolytic system, with strong potential for applications requiring endoglucanase activity. Overall, the findings highlight the Amazon rhizosphere as a valuable reservoir of cellulolytic bacteria and support the biotechnological relevance of native rhizobacteria for sustainable biomass conversion processes.