Designing a novel signal sequence for efficient secretion of Candida antarctica lipase B in E. coli: The molecular dynamic simulation, codon optimization and statistical analysis approach

Lipases represent an important industrial biocatalysts group displaying enantioselectivity, high stability in solvents and substrate specificity. A commonly used commercial enzyme for synthesis of organic materials is Candida antarctica lipase B (CALB). Its Industrial production involves cost-effective purification of large amounts of microbially-produced macromolecules. Hence, great focus is now placed on periplasmic secretion and storage. Accordingly, we designed and constructed a suitable signal peptide for secretion of lipase using a newly developed software. Molecular dynamic simulation was performed to compare structural states of native signal peptide of Staphylococcus aureus protein A (nSpA) and its modified counterpart (mSpA). Furthermore, the effect of these two peptides in binding to the signal peptidase I (SPase I) was studied. Simulation data confirmed experimental results showing that secondary structure of the mSpA binding region and the binding site of the SPase I create a more stable interaction relative to native SpA. Subsequently, response surface methodology (RSM) was employed to improve secretion. Lactose concentration, induction time and temperature were identified as essential parameters to optimize the expression and periplasmic secretion of CALB. mSpA increased CALB expression levels by 2.1-fold relative to the control, which further confirmed efficient secretion of the mature enzyme through the Sec-dependent pathway.