Investigation on starch and cellulose degradation, siderophore production and potassium solubilization of rhizosphere bacteria isolated from sugarcanes cultivated in Ben Cau district, Tay Ninh province, Vietnam

Rhizobacteria play a crucial role in enhancing plant growth through various mechanisms, including nutrient solubilization and decomposition of complex organic compounds. This study aimed to evaluate the potential of 31 rhizobacteria strains, isolated from the rhizosphere of sugarcane (Saccharum spp.) cultivated in Ben Cau district, Tay Ninh province, Vietnam, for starch and cellulose decomposition, siderophore synthesis, and potassium solubilization. The ability of the strains to degrade starch and cellulose was determined by agar well diffusion approach. The ability of siderophore synthesis was investigated by using the Chrome Azurol Sulfonate (CAS) assay. Potassium solubilization was quantified using the sodium tetraphenylborate method, measuring the release of soluble potassium from insoluble sources. The result showed that 74% of the strains were capable of hydrolyzing starch, with strain BC45 exhibiting the strongest activity, forming a halo zone diameter of 1.80 ± 0.20 cm. 87% of the strains showed the ability to degrade cellulose, with strains BC12 and BC49 demonstrating the highest activity, producing clearing zone diameters of 1.87 ± 0.12 cm and 1.73 ± 0.46 cm, respectively. Notably, all strains were capable of releasing soluble potassium from insoluble potassium, with BC06 showing the highest capability with K2O concentrations of 35.23 mg/L. Additionally, 42% of the strains were able to produce siderophores. This study demonstrated that the isolated rhizobacteria possessed significant potential for starch and cellulose decomposition, potassium solubilization, and siderophore production. These findings suggest that these strains could be valuable candidates for the development of biofertilizers and biostimulants to improve sugarcane cultivation in the region.