Microbial diversity and community structure in co-composted bamboo powder and tea leaves based on carbon substrate utilization patterns of the BIOLOG EcoPlate method

This study clarified the functional characteristics of microorganisms during the co-composting of bamboo powder and tea leaves. Three treatments were established for 14 weeks of composting: B100 (600 kg bamboo powder), B40 (240 kg bamboo powder and 360 kg tea leaves), and B20 (120 kg bamboo powder and 480 kg tea leaves), with two replicates each. The functional characteristics of the microorganisms were analyzed using a BIOLOG EcoPlate for carbon substrate utilization patterns using kinetic parameters, microbial diversity analysis by calculating diversity indices, and microbial community structure analysis via principal component analysis of kinetic parameters. When bamboo powder was composted alone, the microbial diversity was high in the early composting stage because of the utilization of the rich and complicated carbon substrates. However, in the late composting stage, the microbial diversity was low because of the utilization of poor and simple carbon substrates. In contrast, when bamboo powder and tea leaves were combined, carbon substrate utilization and microbial diversity were low during the early composting stage. In the middle and late stages of composting, abundant carbon substrates became available, and microbial diversity increased. Differences in carbon substrate utilization patterns can be separated by microbial community structure analysis, especially at the end of composting. The communities were divided according to the proportions of bamboo powder and tea leaves. In the early stage of co-composting bamboo powder and tea leaves, microbial activity decreased because of the lower compost temperature and higher tea polyphenol content. However, in the middle and late stages, microbial activity may increase owing to the supply of tea-derived soluble sugars and amino acids. The co-composting of bamboo powder and tea leaves may enhance microbial activity, diversity, and carbon substrate utilization during the middle and late composting stages.