Rational Design of Alginate Lyase AlgL3199 for Thermal Stability and Specific Activity Enhancement

Alginate lyase is a critical enzyme that catalyzes alginate degradation; however, its low thermal stability limits its industrial application. This study proposes a feasible and efficient rational design strategy based on computer-aided structure analysis and energy calculation for generating thermally stable alginate lyases. Through site-directed mutagenesis, we obtained four thermal stability-enhanced mutants, namely K81A, D148P, K81A/D148P, and K81A/D148P/V163T, which exhibited 5.18-, 4.66-, 3.22-, and 3.53-fold longer half-lives, respectively, than AlgL3199 at 60 °C. Additionally, K81A, D148P, K81A/D148P, and K81A/D148P/V163T showed 28.59%, 42.56%, 34.71%, and 12.15% increased specific activities, respectively, compared to AlgL3199. Structural and hydrophobicity analyses revealed that the obtained mutants showed enhanced hydrogen-bond networks, structural rigidity, and hydrophobic interactions. Among the four mutants, K81A exhibited the most pronounced structural modification. The findings of this study indicate that the proposed rational design strategy provides a valuable method for improving both thermal stability and specific activity of alginate lyases.