Thermophilic Bacteria from Surface Layer of Compost: Isolation and Characterization During the Processing Stage

Ningtyas, Alvina Gian Sinta and Irawan, Bambang and Setiawan, Wawan Abdullah and Handayani, Kusuma (2025) Thermophilic Bacteria from Surface Layer of Compost: Isolation and Characterization During the Processing Stage. GSC Biological and Pharmaceutical Sciences, 32 (1). pp. 165-175. ISSN 2581-3250

Composting is a decomposition process of organic waste that occurs aerobically with the assistance of decomposer agents under controlled conditions. Thermophilic bacteria are one group of decomposer microorganisms that play a role in composting during the thermophilic phase. This study aims to isolate and characterize thermophilic bacteria from the surface layer of compost during the processing stage at PT Great Giant Pineapple’s Compost Plant, with the expectation of accelerating the composting process. This research was conducted using an exploratory descriptive method, with stages including sampling of surface-layer compost, isolation of thermophilic bacteria, purification of bacterial isolates, macroscopic and microscopic morphological characterization, and enzymatic activity assays. The results showed that seven bacterial isolates were obtained. The colony morphology of the seven isolates was dominated by irregular and spreading forms with varied margins, such as irregular, wooly, undulate, and entire. Most colonies showed raised elevations and shared a uniform cream coloration. Microscopically, all isolates were rod-shaped, Gram-positive, and capable of forming spores. Isolates ALV1, ALV2, ALV3, ALV4, ALV5, ALV6, and ALV7 demonstrated the ability to produce amylase and protease enzymes, while only ALV1, ALV2, ALV3, ALV5, and ALV6 were capable of producing cellulase enzymes. The highest enzymatic index (EI) values for amylase and cellulase were observed in ALV6, at 8.38 and 14.66 respectively, whereas the highest protease EI value was recorded in ALV4, at 4.39.