Partitioning of xylanase from Thermomyces lanuginosus in PEG/NaCit aqueous two-phase systems: Structural and functional approach

•PEG protects xylanase from thermal denaturation.•Xylanase preferentially partitions into the PEG-rich phase.•Partitioning of xylanase is also driven by the excluded volume effect.•Xylanase partitions in PEG1000/NaCit.

The structure and catalytic activity of xylanase from Thermomyces lanuginosus were studied in different media (containing polyethylene glycol -PEG- or salt) at different temperatures. The aim was to study how the native structure of the enzyme is affected to understand the partitioning behavior of xylanase in PEG/sodium citrate (PEG/NaCit) aqueous two-phase systems. The presence of PEGs of different molar masses slightly altered the native structure of xylanase, although its catalytic activity was not affected. All the polymers assayed protect the native structure (and catalytic activity) of xylanase against temperature, except for PEG1000. Surface hydrophobicity experiments showed that xylanase favorable interacts with PEGs. Partitioning experiments confirmed this result and demonstrated that PEG1000/NaCit is the best system to partition xylanase from Thermomyces lanuginosus, since the Kp was 17.7 ± 0.3.