A facile approach was developed to immobilize gold nanoparticles (AuNPs) onto peptide nanofibers for catalytic applications. In this study, fluorenylmethoxycarbonyl diphenylalanine (Fmoc-FF) was conjuncted with histidine, arginine or cysteine at their C-terminus to provide binding sites for AuNPs. The co-assembly of Fmoc-tripeptide and AuNPs was achieved by dropping the peptide monomer solution directly into the AuNP solution, leading to the formation of nanofibers and the immobilization of AuNPs in one step. Atomic force microscopy, transmission electron microscope and circular dichroism analyses demonstrated that the presence of AuNPs does not significantly change the morphology and secondary structure of the nanofibers. The histidine-containing peptide-immobilized AuNPs were found to display favorable catalytic activity and stability for the reduction of 4-nitrophenol to 4-aminophenol. The present approach to fabricating nanomaterial-supported AuNPs may be extended to the production of other nanoparticle-containing composites in the fields of catalysis, sensing and biomedicine.

A recyclable strategy for the production of high-purity (>95%) galacto-oligosaccharides (GOS) was developed using Kluyveromyces lactis in both the synthesis and purification steps. For the synthesis of GOS, ethanol-permeabilized cells (p-cells) of K. lactis were used because the enhanced permeability facilitated the mass transfer of the substrate and the release of oligosaccharide products. For the purification of GOS, non-permeabilized K. lactis cells (np-cells) were preferred as a result of their intrinsic cell membrane barrier toward GOS, which led to the selective consumption of carbohydrate. In this way, undesired glucose, galactose, and lactose in the raw GOS solution can be completely removed. This strategy is recyclable not only because of the high stability and reusability of p-cells and np-cells but also because the ethanol, which is simultaneously generated during the purification, can be reused for the preparation of p-cells. The strategy proposed in this study is a promising candidate for the efficient production of high-purity GOS.