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Journal of Environmental Microbiology

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Thermophilic lignocellulolytic microorganisms in compost: characterization

Author(s): Jonah Anguka*

In order to compost, a microbiota must be chosen that can withstand the high temperatures produced by the process and degrade the lignocellulose. To increase composting efficiency and offer thermostable biomass-degrading enzymes for biorefineries, it is important to have a thorough understanding of the thermophilic microbial population involved in such biotransformation. This study focused on the dynamics, enzymes, and thermotolerance of each member of a lignocellulose-degrading thermophilic microbial community during all stages of composting plant waste. The results showed that 58% of holocellulose (cellulose + hemicellulose) and 7% of lignin had been destroyed at the end of composting.In contrast to 8%-10% of thermophilic bacteria, which only demonstrated this feature for hemicellulose degradation, the entire fungal thermophilic population exhibited lignocellulose-degrading ability (xylan-degrading). Both groups play a significant role in the breakdown of hemicellulose throughout the entire process due to their abundance, enzymatic activity, and wide range of thermotolerance, whereas the degradation of cellulose and lignin is only possible due to the activity of a few thermophilic fungi that persist at the end of the process. The 159 xylanolytic bacteria isolates were mostly from the Firmicutes (96%) order, with a few Actinobacteria (2%), and Proteobacteria (2%). Aeribacillus pallidus and Bacillus licheniformis were the two most common species. Only 4 species- Thermomyces lanuginosus, Talaromyces thermophilus, Aspergillus fumigatus, and Gibellulopsis nigrescens of the 27 strains of thermophilic fungi were dominant, with A. fumigatus and T. lanuginosus the other two species. As a result of the shifting composting environment, several strains of the same species emerged separately at different phases of composting, exhibiting phenotypes with variable thermotolerance and unique enzyme expression that had not been previously recorded for the species. Potential candidates for the synthesis of thermozymes were identified as Bacillus thermoamylovorans, Geobacillus thermodenitrificans, T. lanuginosus, and A. fumigatus strains with high enzyme activity. This study establishes the groundwork for future research into how thermophilic lignocellulolytic bacteria adapt and acquire new features during composting, as well as their potential use in biotechnological processing.

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