Biobased Sunflower Stalk Matrix for Lipase Stabilization via Physical Adsorption

The search for sustainable, cost-effective biocatalytic processes has driven efforts to develop low-cost supports for enzyme immobilization. Lignocellulosic residues have received particular attention due to their abundance, renewability, and structural properties. Despite the growing interest in lignocellulosic residues as enzyme supports, sunflower stalks remain largely unexplored for lipase immobilization. This study aims to evaluate the use of sunflower stalks (Helianthus annuus L.), in natura and after alkaline and hydrothermal pretreatments, as supports for the immobilization of Burkholderia cepacia lipase by physical adsorption. Pretreatment improved enzyme performance, increasing thermal stability by up to 4.28-fold compared to the free enzyme. The biocatalysts prepared using alkaline-treated, hydrothermal-treated, in natura supports, and free enzyme showed half-life values of 19.95, 16.86, 10.25, and 4.66 h, respectively. Immobilization also enhanced enzyme reusability, particularly for the alkaline-treated support, which maintained activity for up to six operational cycles. Kinetic analysis of the immobilized enzyme showed reduced V_max and apparent K_m values, suggesting changes in enzyme-substrate interactions and possible diffusion limitations. These results indicate that pretreatment plays an important role in modifying the physicochemical properties of sunflower stalks, directly affecting the stability and reusability of the biocatalyst. Overall, this study highlights the potential of sunflower stalk residues as a low-cost and effective support with improved catalytic performance and operational stability.