Concommitant adaptation of a GH11 xylanase by directed evolution to create an alkali-tolerant/thermophilic enzyme

Author(s)

Ruller, Roberto ^{[1, 2]} ; Alponti, Juliana ^[1] ; Deliberto, Laila Aparecida ^[1] ; Zanphorlin, Leticia Maria ^[2] ; Machado, Carla Botelho ^{[1, 2]} ; Ward, Richard John ^{[1, 2]}

Affiliation

^[1] Univ Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao Preto, Dept Quim, BR-14040901 Ribeirao Preto, SP - Brazil

^[2] CNPEM, Lab Nacl Ciencia & Tecnol Bioetanol CTBE, Campinas, SP - Brazil

• Document type: Journal article
• Source: PROTEIN ENGINEERING DESIGN & SELECTION; v. 27, n. 8, p. 255-262, AUG 2014.
• Web of Science Citations: 12

Abstract

As part of an ongoing directed evolution program, the catalytic performance of the Xylanase A from Bacillus subtilis (XynA), which presents temperature and pH optima of 50 degrees C and 6.0, respectively, has been enhanced to create a highly thermostable and alkali-tolerant enzyme. A library of random XynA mutants generated by error-prone polymerase chain reaction was screened by halo formation on agar containing xylan at pH 8.0. Two mutants showing higher catalytic activity at elevated pH in relation to the wild-type XynA were selected, and pooled with a further 5 XynA variants selected by screening thermostable XynA obtained from a previous directed evolution study for activity at alkaline pH. This pool of variants was used as a template for a further round of error-prone polymerase chain reaction and DNase fragment shuffling, with screening at pH 12.0 at 55 degrees C. Selected mutants were subjected to further DNase shuffling, and a final round of screening at pH 12.0 and 80 degrees C. A XynA variant containing eight mutations was isolated (Q7H/G13R/S22P/S31Y/T44A/I51V/I107L/S179C) that presented a temperature optimum of 80 degrees C, a 3-fold increase in the specific activity compared with the wild-type enzyme at pH 8.0, and a 50% loss of activity (t(50)) of 60 min at 80 degrees C (wild type <2 min). This directed evolution strategy therefore allows the concomitant adaption of increased thermostability and alkali tolerance of an endo-xylanase. (AU)

• FAPESP's process: 10/18850-2 - Identification, characterization and engineering of plant cell wall degrading enzymes
• Grantee: Richard John Ward
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 08/05181-5 - Bioprospecting Celulases for Biorefinary of Biomass using Metagenomic Strategies.
• Grantee: Carla Botelho Machado
• Support Opportunities: Scholarships in Brazil - Doctorate