Extraction of endoglucanase I (Cel7B) fusion proteins from Trichoderma reesei culture filtrate in a poly(ethylene glycol)-phosphate aqueous two-phase system

Anna Collén, Merja Penttilä, Henrik Stålbrand, Folke Tjerneld, Andres Veide

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Abstract

Endoglucanases (EGI) (endo-1,4-β-D-glucan-4-glucanohydrolase, EC 3.2.1.4, Cel7B) of Trichoderma reesei are industrially important enzymes. Thus, there is a great need for development of a primary recovery method suitable for large-scale utilization. In this study we present a concept applicable for large-scale purification of an EGI fusion protein by one-step extraction in a poly(ethylene glycol) PEG-sodium/potassium phosphate aqueous two-phase system. EGI is a two-module enzyme composed of an N-terminal catalytic module and a C-terminal cellulose binding module (CBM) separated by a glycosylated linker region. Partitioning of six different EGI constructs, containing the C-terminal extensions (WP) 2, (WP) 4 or the amphiphilic protein hydrophobin I (HFB) of T. reesei instead of the CBM were studied to evaluate if any of the fusions could improve the partition coefficient sufficiently to be suitable for large-scale production. All constructs showed improved partitioning in comparison to full length EGI. The (WP) 4 extensions resulted in 26- to 60-fold improvement of partition coefficient. Consequently, a relative minor change in amino acid sequence on the two-module protein EGI improved the partition coefficient significantly in the PEG 4000-sodium/potassium phosphate system. The addition of HFBI to EGI clearly enhanced the partition coefficient (K = 1.2) in comparison to full-length EGI (K = 0.035). Partitioning of the construct with (WP) 4 fused to the catalytic module and a short sequence of the linker [EGI core-P5(WP) 4] resulted in the highest partition coefficient (K = 54) and a yield of 98% in the PEG phase. Gel electrophoresis showed that the construct with the (WP) 4 tag attached after a penta-proline linker could be purified from the other bulk proteins by only a single-step separation in the PEG 4000-sodium/potassium phosphate system. This is a major improvement in comparison with the previously studied model (ethylene oxide-propylene oxide)-dextran system. Hence, this construct will be suitable for further optimization of the extraction of the enzyme in a PEG 4000-sodium/potassium phosphate system from culture filtrate.

Original languageEnglish
Pages (from-to)55-62
Number of pages8
JournalJournal of Chromatography A
Volume943
Issue number1
DOIs
Publication statusPublished - 11 Jan 2002
MoE publication typeA1 Journal article-refereed

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Keywords

  • Aqueous two-phase systems
  • Trichoderma reesei
  • Endoglucanases
  • Enzymes
  • Proteins
  • Sodium phosphate
  • potassium
  • phosphates

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