The secondary structure of lipase 1 from Candida rugosa, a model system for large monomeric enzymes, has been studied by FTIR (Fourier-transform infrared) spectroscopy in water and 2H2O. The secondary structure content, determined by the analysis of the amide I band absorption through second derivative and curve fitting procedures, is in agreement with that estimated by X-ray data and predicts, in addition, the existence of two classes of α-helices. We have also investigated the enzyme stability and aggregation at high temperature by following the protein unfolding. The thermal stability determined by FTIR is in excellent agreement with the temperature dependence of the lipase activity. Furthermore, new insights on the glycosylation of the recombinant protein produced in Pichia pastoris and on its heterogeneity related to different fermentation batches were obtained by the analysis of the IR absorption in the 1200−900 cm−1 carbohydrate region. A drastic reduction of the intensity of this band was found after enzymic deglycosylation of the protein. To confirm that the FTIR absorption in the 1200–900 cm−1 region depends on the carbohydrate content and glycoform distribution, we performed an MS analysis of the protein sugar moieties. Glycosidic structures of the high mannose type were found, with mannoses ranging from 8 to 25 residues.

The synthesis of silver nanoparticles (AgNPs) by microorganisms recently gained a greater interest due to its potential to produce them in various sizes and morphologies. In this study, for AgNP biosynthesis, we used a new Pseudomonas strain isolated from a consortium associated with the Antarctic marine ciliate Euplotes focardii. After incubation of Pseudomonas cultures with 1 mM of AgNO₃ at 22 °C, we obtained AgNPs within 24 h. Scanning electron (SEM) and transmission electron microscopy (TEM) revealed spherical polydispersed AgNPs in the size range of 20–70 nm. The average size was approximately 50 nm. Energy dispersive X-ray spectroscopy (EDS) showed the presence of a high intensity absorption peak at 3 keV, a distinctive property of nanocrystalline silver products. Fourier transform infrared (FTIR) spectroscopy found the presence of a high amount of AgNP-stabilizing proteins and other secondary metabolites. X-ray diffraction (XRD) revealed a face-centred cubic (fcc) diffraction spectrum with a crystalline nature. A comparative study between the chemically synthesized and Pseudomonas AgNPs revealed a higher antibacterial activity of the latter against common nosocomial pathogen microorganisms, including Escherichia coli, Staphylococcus aureus and Candida albicans. This study reports an efficient, rapid synthesis of stable AgNPs by a new Pseudomonas strain with high antimicrobial activity.