Laccase Immobilization on Activated Carbon from Hydrothermal Carbonization of Corn Cob

This study aimed to immobilize laccase on activated carbon produced from corn cob subjected to hydrothermal carbonization. The optimal condition of hydrochar synthesis was determined using a Rotatable Central Composite Design (RCCD), with the oxygen functional groups (OFGs) as the response variable. The carbons were characterized for OFGs content, and multivariate principal component analysis (PCA) was used to correlate the supports OFGs content with the immobilization capacity and derivatives enzymatic activity. Time and temperature optimal conditions were 8.2 h and 232.7 °C. The OF content was 100% higher than the precursor. PCA provided a positive correlation between the derivative enzyme activity and the lactonic groups. The activated carbon produced in the best synthesis conditions presented a point of zero charge of 4.68 ± 0.20, low ash content (3.71% ± 0.02% w/w), and a well-developed porous structure, when compared to hydrochar, presenting a surface area of 719 m 2 g − 1 . The highest immobilization efficiency (99.60% ± 0.05%) and activity (22.54 ± 1.65 U mg − 1 ) were observed at pH 4.0 and 25 °C. The immobilized enzyme obtained under the optimal conditions showed 50% of its initial activity after 5 consecutive cycles of use and maintained 50% of its activity after 30 days of storage. Graphical Abstract