Functional characterization of a bacterial expansin from bacillus subtilis for enhanced enzymatic hydrolysis of cellulose

Eun Sil Kim, Hee Jin Lee, Won Gi Bang, In Geol Choi, Kyoung Heon Kim

Research output: Contribution to journalArticlepeer-review

137 Citations (Scopus)


Expansin is a plant protein family that induces plant cell wall-loosening and cellulose disruption without exerting cellulose-hydrolytic activity. Expansin-like proteins have also been found in other eukaryotes such as nematodes and fungi. While searching for an expansin produced by bacteria, we found that the BsEXLX1 protein from Bacillus subtilis had a structure that was similar to that of a β-expansin produced by maize. Therefore, we cloned the BsEXLX1 gene and expressed it in Escherichia coli to evaluate its function. When incubated with filter paper as a cellulose substrate, the recombinant protein exhibited both cellulosebinding and cellulose-weakening activities, which are known functions of plant expansins. In addition, evaluation of the enzymatic hydrolysis of filter paper revealed that the recombinant protein also displayed a significant synergism when mixed with cellulase. By comparing the activity of a mixture of cellulase and the bacterial expansin to the additive activity of the individual proteins, the synergistic activity was found to be as high as 240% when filter paper was incubated with cellulase and BsEXLX1, which was 5.7-fold greater than the activity of cellulase alone. However, this synergistic effect was observed when only a low dosage of cellulase was used. This is the first study to characterize the function of an expansin produced by a non-eukaryotic source.

Original languageEnglish
Pages (from-to)1342-1353
Number of pages12
JournalBiotechnology and Bioengineering
Issue number5
Publication statusPublished - 2009 Apr 1


  • Bacterial expansin
  • Biofuel
  • Cellulase
  • Cellulose hydrolysis
  • Structural homolog
  • Synergism

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology


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