Cultivation methods, characterization, and biocatalytic potential of organic solid waste degrading bacteria isolated from sugarcane rhizospheric soil and compost

The study aimed to investigate organic waste-degrading microbial communities in compost and sugarcane rhizospheric soil from Kodinar, Gujarat, India and to assess their potential for producing novel bioactive compounds. Compost contained higher total culturable heterotrophic bacteria (1.3 x 108) and cellulolytic bacterial (4 x 106) populations compared to rhizospheric soil. A total of 96 isolates were obtained using various cultivation strategies with 35 isolates obtained through enrichment techniques, and the rest through direct plating on nutrient agar. Remarkably, four isolates CP2, CP4, CP9 and CP11 showed significant lignin hydrolysis. Further, morphological characterization revealed 26 Gram-positive isolates. Based on microscopic, cultural, and biochemical assessments, as well as 16 S rRNA gene sequencing, selective isolates with lignocellulolytic potential were identified as Bacillus licheniformis (SRS 11), Priestia megaterium (SRS 8, CP 5), Bacillus subtilis (CP11), and Priestia flexa (CP 2 & CP 9). Multiple enzyme secretion potential of the isolates was also investigated. Around 16.66% of isolates secreted at least one lytic enzyme such as cellulase, ligninase, amylase, protease, and pectinase, with variable percentages. The salt significantly affected growth and CMCase activity, with strain SRS8 being less tolerant (3% NaCl) compared to CP2, CP9, and CP11, which exhibited activity between 0 and 7% NaCl (w/v). Compost isolates preferred higher temperatures (40-45 degrees C), while most rhizospheric isolates thrived at lower temperatures (35 degrees C). Rhizospheric isolates preferred pH 7. Most compost isolates grew at pH 7, except CP9 and CP11, which showed best growth at pH 8. Overall, the study highlights microbial waste-degrading potential, enzyme production, and environmental preferences.