Simultaneous purification and immobilization of soybean hull peroxidase with a dye attached to chitosan mini-spheres

Construction of arming Yarrowia lipolytica surface-displaying soybean seed coat peroxidase for use as whole-cell biocatalyst

Whole-cell biocatalysts could be used in wide-ranging applications. In this study, a new kind of whole-cell biocatalyst was successfully constructed by genetically immobilizing soybean seed coat peroxidase (SBP) on the cell surface of Yarrowia lipolytica Po1h, using a new integrative surface display expression vector (pMIZY05). The coding sequence of SBP was optimized and chemically synthesized, then inserted into pMIZY05 to generate expression plasmid pMIZY05-oEp. A DNA fragment corresponding to SBP and selection marker expression cassettes, without bacterial sequences, was released from pMIZY05-oEp by enzyme digestion and used to transform host yeast cells. A transformant (CM11) with a high recombinant SBP activity of 1571.9 U/mL was obtained, and recombinant SBP was proved to be successfully anchored on cell surface by testing the activities of different cellular fractions. After optimization of culture conditions, the recombinant SBP activity of CM11 was increased to 4187.8 U/mL. Afterwards, biochemical properties of the recombinant SBP were determined: optimum catalytic conditions were 37.5℃ at pH 3.5, and recombinant SBP exhibited high stability during thermal or acidic treatment. Recombinant activity of cell-displayed SBP was re-examined at optimum temperature and pH, which promoted an increase up to 4432.5 U/mL. To our knowledge, this represents the highest activity ever reported for heterologous expression of SBP. This study also provides a useful strategy for heterologous expression of proteins which could be toxic to intracellular content of host cells.

Human Immunoglobulin G Adsorption in Epoxy Chitosan/Alginate Adsorbents: Evaluation of Isotherms by Artificial Neural Networks

This work aimed to evaluate the interaction of human IgG in non-conventional adsorbents based on chitosan and alginate in the absence and presence of Reactive Green, Reactive Blue and Cibacron Blue immobilized as ligands. The adsorption was evaluated at 277, 288, 298 and 310 K using sodium phosphate buffer, pH 7.6, at 25 mmol L−1. The highest adsorption capacity was observed in the experiments performed with no immobilized dye, although all showed adsorption capacity higher than 120 mg g−1. Data modeling was done using Langmuir, Langmuir-Freundlich and Temkin classical nonlinear models, and artificial neural networks (ANN) for comparison. According to the parameters obtained, a possible adsorption in multilayers was observed due to protein-adsorbent and protein-protein interactions, concluding that IgG adsorption process is favorable and spontaneous. Using an ANN structure with 3 hidden neurons (single hidden layer), the MSE (RMSE) for training, test and validation were 13.698 (3.701), 11.206 (3.347) and 7.632 (2.763), respectively, achieving correlation coefficients of 0.999 in all steps. ANN modeling proved to be effective in predicting the adsorption isotherms in addition to overcoming the difficulties caused by experimental errors and/or arising from adsorption phenomenology.