Abstract
Phenylalanine ammonia-lyase (PAL) catalyzes the nonoxidative deamination of phenylalanine to yield trans-cinnamic acid and ammonia. Recombinant Bambusa oldhamii BoPAL1/2 proteins were immobilized onto electrospun nanofibers by dextran polyaldehyde as a cross-linking agent. A central composite design (CCD)-response surface methodology (RSM) was utilized to optimize the electrospinning parameters. Escherichia coli expressed eBoPAL2 exhibited the highest catalytic efficiency among four enzymes. The optimum conditions for fabricating nanofibers were determined as follows: flow rate of 0.10 mL/h, voltage of 13.8 kV, and distance of 13 cm. The response surface models were used to obtain the smaller the fiber diameters as well as the highest PAL activity in the enzyme immobilization. Compared with free BoPALs, immobilized BoPALs can be reused for at least 6 consecutive cycles. The remained activity of the immobilized BoPAL proteins after storage at 4 °C for 30 days were between 75 and 83%. In addition, the tolerance against denaturants of the immobilized BoPAL proteins were significantly enhanced. As a result, the dextran polyaldehyde natural cross-linking agent can effectively replace traditional chemical cross-linking agents for the immobilization of the BoPAL enzymes. The PAL/nylon 6/polyvinyl alcohol (PVA)/chitosan (CS) nanofibers made are extremely stable and are practical for industrial applications in the future.
Highlights
Phenylalanine ammonia-lyase (PAL, 4.3.1.24) catalyzes the deamination of L-phenylalanine to yield trans-cinnamic acid and ammonia, is one of the crucial steps in the general phenylpropanoid pathway (Figure 1) [1,2]
The prepared immobilized PAL was characterized by Fourier transform infrared spectroscopy (FT-IR)
Electrospun nanofibers are characterized by their enhancement for enzyme immobilization through their high surface area and porosity where their functional surface can hold an excessive number of active sites for immobilization [19,22,28,36]
Summary
Phenylalanine ammonia-lyase (PAL, 4.3.1.24) catalyzes the deamination of L-phenylalanine to yield trans-cinnamic acid and ammonia, is one of the crucial steps in the general phenylpropanoid pathway (Figure 1) [1,2]. Trans-cinnamic acid is well known to exhibit various health-promoting properties including anti-aging, anti-diabetic, anti-inflammatory, anti-microbial and anti-cancer activities [5,6,7,8]. The potential of trans-cinnamic acid as therapeutic agent for other conditions including Alzheimer’s disease, viral infections and tuberculosis [9]. Cinnamic acid derivatives are widely used in cosmetic industries such as perfumes, UV protecting agents [12] as well as possess anti-cancer, antioxidant and anti-microbial properties [13,14,15]
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