Characterization of Thermophilic Lignocellulolytic Microorganisms in Composting

Abstract

Composting involves the selection of a microbiota capable of resisting the high temperatures generated during the process and degrading the lignocellulose. A deep understanding of the thermophilic microbial community involved in such biotransformation is valuable to improve composting efficiency and to provide thermostable biomass-degrading enzymes for biorefinery. This study investigated the lignocellulose-degrading thermophilic microbial culturome at all the stages of plant waste composting, focusing on the dynamics, enzymes, and thermotolerance of each member of such a community. The results revealed that 58% of holocellulose (cellulose plus hemicellulose) and 7% of lignin were degraded at the end of composting. The whole fungal thermophilic population exhibited lignocellulose-degrading activity, whereas roughly 8–10% of thermophilic bacteria had this trait, although exclusively for hemicellulose degradation (xylan-degrading). Because of the prevalence of both groups, their enzymatic activity, and the wide spectrum of thermotolerance, they play a key role in the breakdown of hemicellulose during the entire process, whereas the degradation of cellulose and lignin is restricted to the activity of a few thermophilic fungi that persists at the end of the process. The xylanolytic bacterial isolates (159 strains) included mostly members of Firmicutes (96%) as well as a few representatives of Actinobacteria (2%) and Proteobacteria (2%). The most prevalent species were Bacillus licheniformis and Aeribacillus pallidus. Thermophilic fungi (27 strains) comprised only four species, namely Thermomyces lanuginosus, Talaromyces thermophilus, Aspergillus fumigatus, and Gibellulopsis nigrescens, of whom A. fumigatus and T. lanuginosus dominated. Several strains of the same species evolved distinctly at the stages of composting showing phenotypes with different thermotolerance and new enzyme expression, even not previously described for the species, as a response to the changing composting environment. Strains of Bacillus thermoamylovorans, Geobacillus thermodenitrificans, T. lanuginosus, and A. fumigatus exhibiting considerable enzyme activities were selected as potential candidates for the production of thermozymes. This study lays a foundation to further investigate the mechanisms of adaptation and acquisition of new traits among thermophilic lignocellulolytic microorganisms during composting as well as their potential utility in biotechnological processing.

Effects of mulching film on soil microbial diversity and community of cotton

“…The genus Gibellulopsis was more abundant in the DPBOS treatment than in the PEBOS treatment in both rhizosphere and non-rhizosphere soil. Gibellulopsis had been previously isolated from compost, rotting root soil, and decomposing grains (López et al 2021 ; Kotova et al 2016 ; Tian et al 2021 ). Gibellulopsis is reportedly associated with carbohydrate content.…”

Development of a microbial protease for composting swine carcasses, optimization of its production and elucidation of its catalytic hydrolysis mechanism

“…Although animals or plants produce proteases, microorganisms are regarded as the optimal source of protease production as they are usually simple, cost-effective and highly functional [ 15 ]. Biochemical properties of microbial enzyme are determined by the separation environment of the enzyme-producing strain [ 7 ][ 16 ]. Therefore, it is necessary to select a suitable microbial protease separation environment, in accordance with the proposed microbial protease application, before selecting a microbial protease[ 17 ].…”

Compost-derived thermophilic microorganisms producing glycoside hydrolase activities as new potential biocatalysts for sustainable processes

“…The study of cellulolytic activity of these microorganisms was performed highlighting their potential for cellulose conversion and subsequently, for second generation bioethanol production that represents one of the best alternatives to the fossil fuels [18]. Recently, Lopez et al (2021) [19] described the characterization of thermophilic lignocellulolytic microorganisms in composting process of mixed shredded tomato plant waste (stalks and leaves) with pine chips. The studies revealed that while the complete fungal thermophilic population was characterized by lignocellulose-degrading enzymes, instead only 8-10% of the thermophilic bacteria exhibited them, and in particular enzymatic activities regarding the hemicellulose degradation.…”