Isolation of soil cellulolytic bacteria and their temperature- and pH-dependent decomposition of carboxymethylcellulose-based hydrogels

Cellulose-degrading bacteria play a vital role in the efficient utilization and recycling of cellulose-based resources. This study aimed to isolate and screen native cellulolytic bacteria from low-organic matter sandy loam soil and to evaluate their capacity to degrade cellulose under controlled conditions. A multistep screening strategy was applied to identify optimal cultivation conditions for enhanced cellulase production, using carboxymethyl cellulose (CMC)-based hydrogel as the carbon source. Bacterial isolates were assessed in vitro for cellulase activity, and key enzymatic properties, including optimal pH and temperature, were determined. Five efficient cellulase-producing strains were identified: CB2 (Klebsiella variicola), CB16 (Cohnella plantaginis), CB18 (Microbacterium sp.), CB22 (Chryseobacterium sp.), and CB24 (Chryseobacterium sp.). Enzyme activity, evaluated by clear zone formation and hydrolysis capacity, was highest for strain CB16, which also showed the greatest reducing sugar production. Maximum degradation efficiency occurred at pH 7.0 and 30 °C, resulting in CMC hydrogel weight losses of 43.6 ± 5.5% and 20.9 ± 0.5%, respectively. Scanning electron microscopy revealed pronounced structural alterations and a fibrous form of the hydrogel by day 7, confirming effective hydrolysis. In native soil, CO₂ evolution increased over a 36-day incubation. The highest release had been observed for pristine CMC (0.353 ± 0.019 [Formula: see text]/g_soil) compared to the crosslinked and composite hydrogels. These results highlight the potential of native soil bacteria for biodegradation of cellulose-based materials.