Facile recycling of Escherichia coli and Saccharomyces cerevisiae cells from suspensions using magnetic modification method and mechanism analysis

Biodegradation of poly(ethylene terephthalate) through PETase surface-display: From function to structure

Polyethylene terephthalate (PET) is one of the most used plastics which has caused some environmental pollution and social problems. Although many newly discovered or modified PET hydrolases have been reported at present, there is still a lack of comparison between their hydrolytic capacities, as well as the need for new biotechnology to apply them for the PET treatment. Here, we systematically studied the surface-display technology for PET hydrolysis using several PET hydrolases. It is found that anchoring protein types had little influence on the surface-display result under T7 promoter, while the PET hydrolase types were more important. By contrast, the newly reported FAST-PETase showed the strongest hydrolysis effect, achieving 71.3% PET hydrolysis in 24 h by pGSA-FAST-PETase. Via model calculation, FAST-PETase indeed exhibited higher temperature tolerance and catalytic capacity. Besides, smaller particle size and lower crystallinity favored the hydrolysis of PET pellets. Through protein structure comparison, we summarized the common characteristics of efficient PET-hydrolyzing enzymes and proposed three main crystal structures of PET enzymes via crystal structural analysis, with ISPETase being the representative and main structure. Surface co-display of FAST-PETase and MHETase can promote the hydrolysis of PET, and the C-terminal of the fusion protein is crucial for PET hydrolysis. The results of our research can be helpful for PET contamination removal as well as other areas involving the application of enzymes. SYNOPSIS: This research can promote the development of better PET hydrolase and its applications in PET pollution treatment via bacteria surface-display.

Aptamer-superparamagnetic nanoparticles capture coupling siderophore-Fe3+ scavenging actuated with carbon dots to confer an "off-on" mechanism for the ultrasensitive detection of Helicobacter pylori

The detection of Helicobacter pylori infection in human feces is an appropriate non-invasive diagnostic method. However, the antibody-dependent stool antigen immunoassay bears many challenges. Therefore, we developed an antibody-independent biosensing platform. The core of this platform was a triple-module biosensor. The first module was Ca²⁺-doped superparamagnetic nanoparticles modified with an H. pylori-specific aptamer, functioning to selectively capture H. pylori cells from samples. The second module was a bifunctional co-polymer of chloroprotoporphyrin IX iron (III)-polyethylene glycol-desferrioxamine, which could bind to H. pylori with high affinity and chelate Fe³⁺ from the third module of Fe³⁺-quenched carbon dots (CDs) solution. When the formed module 1-H. pylori-module 2 complexes reacted with module 3, a subsequent magnetic separation could scavenge Fe³⁺, causing fluorescence recovery from quenched CDs as the transducing mechanism. This transducer could respond to tiny changes in Fe³⁺ concentration with distinguishable fluorescence differences, thus conferring the biosensor with high sensitivity, a wide detection range of 10-10⁷ CFU/mL and a limit of detection (LOD) as low as 1 CFU/mL. From simulated human stool samples, H. pylori was enriched with a centrifugal microfluidic plate to eliminate any interference from matrices, and the bacteria were subjected to detection using the biosensor. The actual LOD for the biosensing platform coupling microfluidics and the biosensor was 10¹, and the total time taken was 65 min. This work showcases an instant, accurate, and ultra-sensitive diagnosis of H. pylori in feces.