In this paper, we found a bacteria ( Bacillus wiedmannii MSM) that could not only culture quickly under aerobic condition , but also can biological reduction of Pd (II) under both aerobic and anaerobic conditions. For reducing Pd (II) by Bacillus wiedmannii MSM, the best electron donor was sodium formate and the best growth time was 24 h (mid-log growth phase cells). TEM indicated that a lot of palladium nanoparticles (Pd-NPs) were mainly located in the periplasmic space of the live cells. However, the autoclaved cells could not synthesize Pd-NPs, which proved the role of enzyme in the reduction of Pd (II). A few of Pd-NPs were only formed on the surface of Cu 2+ -treated cells, which proved the main but not the only role of periplasmic hydrogenase in the reduction of Pd (II). XRD and XPS also proved that Pd-NPs could be synthesized by live cells over broad ranges of temperature (20–40 °C) and pH (pH 3.0–7.0). This may be especially useful for in situ reduction and remediation of Pd (II) for both anaerobic and aerobic wastewater.
This study investigated the effects of enzyme action time (1–5 h) on the physicochemical properties, structure, and functionality of transglutaminase-catalyzed ovalbumin (OVA) in the presence of oligochitosan (OCS). Physically combining OVA and OCS led to a substantial increase in particle size and polydispersity index, rendering the mixed system unstable. With the increase of enzyme action time, the particle size of glycosylated and cross-linked OVA (GC-OVA) decreased first and then increased, reaching a minimum value of 411 nm at 4 h. Moreover, the decrease of free amino groups content at 4 h reflected the occurrence degree of glycosylation and cross-linking reaction, which was close to saturation. Diverse methods were used to analyze variations in the molecular structure of OVA, confirming changes in the primary, secondary, and tertiary structures, and the microstructure. The glycosylation grafting and cross-linking with the appropriate extent of the enzymatic action time is the primary reason for improving the foaming , emulsification properties, and DPPH activity of OVA. Moreover, GC-OVA had greater apparent viscosity, G′ and G″ than the other control systems (the untreated OVA and the physical mixture of OVA and OCS) and significantly affected the hardness and cohesion properties in the gel's texture (5.6 and 2.4-fold that of the untreated OVA, respectively). This study provides information for further understanding the effect of glycosylation grafting caused by enzyme cross-linking time on OVA. The study also demonstrates the possibility of obtaining new protein compositions to expand the applications of food proteins.
危险品化学品经营许可证（带存储）