Preparação de biocatalisadores heterogêneos através da imobilização da lipase de Thermomyces lanuginosus em SBA-15 com poros expandidos

Abstract

Lipases play a crucial role in the growth of the bioprocess industry, thanks to their versatile applications in catalyzing a wide range of reactions, such as hydrolysis, esterification of oils and fats, and interesterification reactions. This great versatility makes lipases suitable for use in several areas, including food, biomedicine, cosmetics, biosensors, beverages, detergents, paper, leather and fuels. However, soluble enzymes are unstable under operating conditions and difficult to separate from the reaction medium, which can result in protein contamination of the final product. To overcome these challenges, our research group has studied several enzyme immobilization systems, using a variety of materials as supports. Enzyme immobilization is extremely advantageous, as it offers better process control, allowing reuse, ease of separation of the reaction medium, in addition to potentially improving the properties of the enzyme (stability, activity, selectivity or specificity) and reducing the effects of inhibitors. Thus, the disadvantages of using enzymes in their free form are overcome through immobilization, making it a valuable technique to improve the application of enzymes at an industrial level. Lipases have a common property: in a homogeneous medium, they have their active center isolated from the medium by a polypeptide chain called a lid. In contact with hydrophobic surfaces, this lid moves and exposes the active site to the reaction medium, providing adsorption of the lipase in the open form, so that there may be an increase in enzymatic activity after immobilization, enabling an increase in the efficiency of the process. Therefore, Thermomyces lanuginosus lipase (TLL) has a large lid and can provide the advantages mentioned above. Therefore, this work proposes to study the production of heterogeneous, active and stable biocatalysts, by immobilizing the lipase TLL on mesoporous silica of the Santa Barbara Amorphous-15 type (SBA-15), a partially hydrophobic support, with important characteristics in terms of refers to the high thermal and mechanical stability of this material. In this way, heterogeneous biocatalysts were prepared by adsorption of TLL lipase onto uncalcined (SBAUC-TLL biocatalyst) and calcined (SBAC-TLL biocatalyst) SBA-15, using ammonium fluoride as a pore expander to facilitate TLL immobilization. At an enzyme load of 1 mg/g, high immobilization yields (>90%) and recovered activities (>80% for SBAUC-TLL and 70% for SBAC-TLL) were achieved. When increasing the enzyme load to 5 mg/g, the immobilization yield of SBAUC-TLL was 80% and a recovered activity of 50%, while SBAC-TLL had a yield of 100% and a recovered activity of 36%. Crosslinking with glutaraldehyde (GA) was conducted to improve stability (SBAUC-TLL-GA and SBAC-TLL-GA). Although SBAC-TLL-GA lost 25% of initial activity after GA modifications, it exhibited the highest thermal stability (t1/2 = 5.7 h at 65 ºC), when compared to SBAC-TLL (t1/2 = 12 min) and the soluble enzyme (t1/2 = 36 min), and operational stability (retained 100% activity after 5 cycles). The SBAC-TLL and SBAC-TLL-GA biocatalysts presented high storage stability (4 °C; 90 days) since they retained 100% of initial activity for 30 days. These results highlight SBA-15's potential as an enzyme support and the protocol's efficacy in enhancing stability, with implications for industrial applications in the food, chemical, and pharmaceutical sectors.