Isolation, Biochemical Characterisation and Identification of Thermotolerant and Cellulolytic Paenibacillus lactis and Bacillus licheniformis

Research background. Cellulose is an ingredient of waste materials that can be converted to other valuable substances. This is possible provided that the polymer molecule is degraded to smaller particles and used as a carbon source by microorganisms. Because of the frequently applied methods of pretreatment of lignocellulosic materials, the cellulases derived from thermophilic microorganisms are particularly desirable. Experimental approach. We were looking for cellulolytic microorganisms able to grow at 50 degrees C and we described their morphological features and biochemical characteristics based on carboxymethyl cellulase (CMCase) activity and the API (R) ZYM system. The growth curves during incubation at 50 degrees C were examined using the BioLector (R) microbioreactor. Results and conclusions. Forty bacterial strains were isolated from fermenting hay, geothermal karst spring, hot spring and geothermal pond at 50 degrees C. The vast majority of the bacteria were Gram-positive and rod-shaped with the maximum growth temperature of at least 50 degrees C. We also demonstrated a large diversity of biochemical characteristics among the microorganisms. The CMCase activity was confirmed in 27 strains. Hydrolysis capacities were significant in bacterial strains: BBLN1, BSO6, BSO10, BSO13 and BSO14, and reached 2.74, 1.62, 1.30, 1.38 and 8.02 respectively. Rapid and stable growth was observed, among others, for BBLN1, BSO10, BSO13 and BSO14. The strains fulfilled the selection conditions and were identified based on the 16S rDNA sequences. BBLN1, BSO10, BSO13 were classified as Bacillus licheniformis, whereas BSO14 as Paenibacillus lactis. Novelty and scientific contribution. We described cellulolytic activity and biochemical characteristics of many bacteria isolated from hot environments. We are also the first to report the cellulolytic activity of thermotolerant P. lactis. Described strains can be a source of new thermostable cellulases, which are extremely desirable in various branches of circular bioeconomy.

Automated summary

The study isolated 40 bacterial strains with cellulolytic activity, most of which were Gram-positive rod-shaped bacteria capable of growth at a minimum of 50 degrees C. Several strains exhibited significant carboxymethyl cellulase (CMCase) activity and hydrolysis capacities, with some identified as Bacillus licheniformis and Paenibacillus lactis. These thermotolerant strains offer potential as a source of new thermostable cellulases for various applications in circular bioeconomy.