Biodegradation of leaf compost by thermophilic cellulolytic bacteria isolated from compost

Abstract

This study aims to isolate and screen bacteria with degrading cellulose at high temperature capacity and to investigate the effectiveness of isolated bacteria in fresh leaf compost degradation. Bacteria were isolated from 4 types of leaf compost consisting of compost Day 7, Month 1, Month 2, and Month 3 which the main raw material of composting was leaf debris collected from Chulalongkorn University. Bacterial strains were isolated using carboxymethyl cellulose (CMC) media, and 79 bacterial strains were obtained. After that, cellulolytic bacteria were screened using Gram’s iodine technique. There were 44 strains of bacteria can decompose cellulose at high temperatures (60ºC). Cellulolytic bacteria were screened by observing the presence of clear zone around each bacterial colony. Hydrolysis capacity (HC) values, which is calculated from the diameter of the clear zone of all 44 strains were analyzed statistically to rank HC values from all bacteria strains. It was found that 11 bacterial strains had greater HC value than the third quartile and D08 showed the highest HC value at 4.92. All 11 bacterial strains were selected for the cellulase assay to assess which bacterial strain had the highest degradability and used for investigating the efficiency in fresh leaf compost decomposition. Due to the epidemic of Covid-19 in Thailand unfortunately, this study was unable to achieve all the proposed objectives.