High cellulolytic potential of the Ktedonobacteria lineage revealed by genome-wide analysis of CAZymes

Yu Zheng, Mayumi Maruoka, Kei Nanatani, Masafumi Hidaka, Naoki Abe, Jun Kaneko, Yasuteru Sakai, Keietsu Abe, Akira Yokota, Shuhei Yabe

Research output: Contribution to journalArticlepeer-review

Abstract

Traditionally, filamentous fungi and actinomycetes are well-known cellulolytic microorganisms that have been utilized in the commercial production of cellulase enzyme cocktails for industrial-scale degradation of plant biomass. Noticeably, the Ktedonobacteria lineage (phylum Chloroflexi) with actinomycetes-like morphology was identified and exhibited diverse carbohydrate utilization or degradation abilities. In this study, we performed genome-wide profiling of carbohydrate-active enzymes (CAZymes) in the filamentous Ktedonobacteria lineage. Numerous CAZymes (153–290 CAZymes, representing 63–131 glycoside hydrolases (GHs) per genome), including complex mixtures of endo- and exo-cellulases, were predicted in 15 available Ktedonobacteria genomes. Of note, 4–28 CAZymes were predicted to be extracellular enzymes, whereas 3–29 CAZymes were appended with carbohydrate-binding modules (CBMs) that may promote their binding to insoluble carbohydrate substrates. This number far exceeded other Chloroflexi lineages and were comparable to the cellulolytic actinomycetes. Six multi-modular extracellular GHs were cloned from the thermophilic Thermosporothrix hazakensis SK20-1T strain and heterologously expressed. The putative endo-glucanases of ThazG5-1, ThazG9, and ThazG12 exhibited strong cellulolytic activity, whereas the putative exo-glucanases ThazG6 and ThazG48 formed weak but observable halos on carboxymethyl cellulose plates, indicating their potential biotechnological application. The purified recombinant ThazG12 had near-neutral pH (optimal 6.0), high thermostability (60°C), and broad specificity against soluble and insoluble polysaccharide substrates. It also represented described a novel thermostable bacterial β-1,4-glucanase in the GH12 family. Together, this research revealed the underestimated cellulolytic potential of the Ktedonobacteria lineage and highlighted its potential biotechnological utility as a promising microbial resource for the discovery of industrially useful cellulases.

Original languageEnglish
Pages (from-to)622-630
Number of pages9
JournalJournal of Bioscience and Bioengineering
Volume131
Issue number6
DOIs
Publication statusPublished - 2021 Jun

Keywords

  • Carbohydrate-active enzymes
  • Cellulases
  • Cellulolytic bacteria
  • Chloroflexi
  • Ktedonobacteria
  • Thermosporothrix hazakensis
  • Thermostable endo-β-1,4-glucanase

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology

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