Preparation and application of high-performance biocatalysts constitute one of the most important aspects of industrial bio-technology. Electrospun nanofibers have a one-dimensional nanostructure, offering promising characteristic for the preparation of high-performance immobilized biocatalysts. Influences of simple inorganic salt incorporated in nanofibers on protein-materials interactions have been ignored in previous studies. Researchers from Institute of Process Engineering, CAS made in depth studies on the manipulating mechanism of inorganic salts on the performance of immobilized enzymes.

LiCl is a kosmotrope that generally promotes protein salvation in aqueous solutions. We found that LiCl embedded in electrospun polymeric nanofibers interestingly induced an abnormal proteinadsorption and substantially augmented the adsorption capacity of the fibers. A unique method that applied a multilayer-immobilization strategy was therefore proposed to prepare nanofibrous lipase for biodiesel synthesis. LiCl co-electrospun with polyurethane nanofibers enabled strong physical adsorption of bovine serum albumin (BSA), forming the first layer of protein on the nanofibers; lipase AK was subsequently crosslinked to BSA as an outer layer of enzyme.

The content of LiCl co-electrospun with polyurethane nanofibers was found to be a sensitive factor affecting the activity and stability of the immobilized lipase. For biodiesel synthesis from soybean oil and methanol in isooctane, the reaction rate catalyzed by nanofibrious lipase carrying 5 wt% LiCl was 6.6-fold higher than fibers without LiCl, with a conversion of 91% was achieved within 2h. LiCl also induced much improved enzyme stability. The nanofibrous lipase with 5% LiCl could be repeatedly used for 42 cycles without apparent activity loss, while the immobilized lipase without LiCl lost over 90% activity within 13 reuse cycles.