Deciphering key residues governing thermostability in Thermomyces lanuginosus lipase through Gibbs free energy-guided engineering.

Lipases serve as indispensable biocatalysts in many industrial applications due to their versatile catalytic abilities. To ensure their thermal resilience of the harsh biological treatment in industry, it is crucial to identify key residues which might impact thermostability. Here, computational design was adopted to decode the stability-determining residues in Thermomyces lanuginosus lipase (TLL). Systematic Gibbs free energy profiling of potent TLL single-point mutational candidates predicted proline 256 (P256) as a thermal liability hotspot. Saturation mutagenesis at P256 discovered that among nineteen P256 variants: (1) five P256 variants exhibited increased melting temperature (ΔT up to 2°C); (2) six variants displayed an optimum temperature with 5-10°C elevation; (3) five P256 variants retained up to 21 % higher residual activity after incubation at 80°C. Furthermore, both P256E and P256I demonstrated synergistic improvements in biodiesel conversion rates, P256I specifically exhibited long-term and recycling stability. Molecular dynamics simulations revealed that the substitutions in P256A/E/I/K with compensatory main-chain rotational freedom, facilitating hydrogen bonding network with both upstream and downstream residues, thereby preserving local structural stability. This study pioneers the identification of P256 as a critical residue governing TLL thermostability. Furthermore, our Gibbs-guided engineering strategy generates multi-property-enhanced lipase variants, directly addressing industrial demands.