Enhanced activity of hyperthermostable Pyrococcus horikoshii endoglucanase in superbase ionic liquids

Hakim Hebal, Joonas Hämäläinen, Laura Makkonen, Alistair W.T. King, Ilkka Kilpeläinen, Sandip Bankar, Nawel Boucherba, Ossi Turunen (Corresponding Author)

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Objectives: Ionic liquids (ILs) that dissolve biomass are harmful to the enzymes that degrade lignocellulose. Enzyme hyperthermostability promotes a tolerance to ILs. Therefore, the limits of hyperthemophilic Pyrococcus horikoschii endoglucanase (PhEG) to tolerate 11 superbase ILs were explored. Results: PhEG was found to be most tolerant to 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) in soluble 1% carboxymethylcellulose (CMC) and insoluble 1% Avicel substrates. At 35% concentration, this IL caused an increase in enzyme activity (up to 1.5-fold) with CMC. Several ILs were more enzyme inhibiting with insoluble Avicel than with soluble CMC. Km increased greatly in the presence ILs, indicating significant competitive inhibition. Increased hydrophobicity of the IL cation or anion was associated with the strongest enzyme inhibition and activation. Surprisingly, PhEG activity was increased 2.0–2.5-fold by several ILs in 4% substrate. Cations exerted the main role in competitive inhibition of the enzyme as revealed by their greater binding energy to the active site. Conclusions: These results reveal new ways to design a beneficial combination of ILs and enzymes for the hydrolysis of lignocellulose, and the strong potential of PhEG in industrial, high substrate concentrations in aqueous IL solutions.

Original languageEnglish
Pages (from-to)961-974
Number of pages14
JournalBiotechnology Letters
Volume44
Issue number8
DOIs
Publication statusPublished - Jun 2022
MoE publication typeA1 Journal article-refereed

Keywords

  • Biomass engineering
  • Enzyme inhibition
  • Enzyme kinetics
  • Hyperthermostable endoglucanase
  • Ionic liquids
  • Cellulose/metabolism
  • Cellulase/metabolism
  • Pyrococcus horikoshii/metabolism
  • Cations
  • Biomass
  • Ionic Liquids/chemistry

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