Surface engineered recombinant Escherichia coli for the potential application of the cobalt contaminated wastewater treatment and the photocatalytic dye degradation

The novel recombinant Escherichia coli strain was construct through cell surface display for the treatment of cobalt contaminated wastewater and dye contaminated wastewater. First, structural analysis of known cobalt binding peptide was conducted and core binding sites were figured out which showing better cobalt binding ability. The cobalt peptides were attached to OmpC to construct cobalt adsorbing recombinant Escherichia coli. The recombinant strain efficiently absorbed and retrieved cobalt from cobalt wastewater by adsorbing 1895 µmol/g DCW of cobalt. Following adsorption, cobalt nanoparticles were synthesized through thermal decomposition of cobalt adsorbed recombinant strain at 500˚C. The nanoparticles exhibited noteworthy photocatalytic properties, demonstrating a substantial capacity for degrading dyes when used as a catalyst at a concentration of 10 mg/dl. These results presenting potential solutions for effective and environmentally friendly approaches to address cobalt and dye contaminated wastewater treatment process.

Construction of Cupriavidus necator displayed with superoxide dismutases for enhanced growth in bioelectrochemical systems

It is of great significance to utilize CO2 as feedstock to synthesize biobased products, particularly single cell protein (SCP) as the alternative food and feed. Bioelectrochemical system (BES) driven by clean electric energy has been regarded as a promising way for Cupriavidus necator to produce SCP from CO2 directly. At present, the key problem of culturing C. necator in BES is that reactive oxygen species (ROS) generated in cathode chamber are harmful to bacterial growth. Therefore, it is necessary to find a solution to mitigate the negative effect of ROS. In this study, we constructed a number of C. necator strains displayed with superoxide dismutase (SOD), which allowed the decomposition of superoxide anion radical. The effects of promoters and signal peptides on the cell surface displayed SOD were analyzed. The proteins displayed on the surface were further verified by the fluorescence experiment. Finally, the growth of C. necator CMS incorporating a pBAD-SOD-E-tag-IgAβ plasmid could achieve 4.9 ± 1.0 of OD600 by 7 days, equivalent to 1.7 ± 0.3 g/L dry cell weight (DCW), and the production rate was 0.24 ± 0.04 g/L/d DCW, around 2.7-fold increase than the original C. necator CMS (1.8 ± 0.3 of OD600). This study can provide an effective and novel strategy of cultivating strains for the production of CO2-derived SCP or other chemicals in BES.

Prospects and applications of synergistic noble metal nanoparticle-bacterial hybrid systems

Hybrid systems composed of living cells and nanomaterials have been attracting great interest in various fields of research ranging from materials science to biomedicine. In particular, the interfacing of noble metal nanoparticles and bacterial cells in a single architecture aims to generate hybrid systems that combine the unique physicochemical properties of the metals and biological attributes of the microbial cells. While the bacterial cells provide effector and scaffolding functions, the metallic component endows the hybrid system with multifunctional capabilities. This synergistic effort seeks to fabricate living materials with improved functions and new properties that surpass their individual components. Herein, we provide an overview of this research field and the strategies for obtaining hybrid systems, and we summarize recent biological applications, challenges and current prospects in this exciting new arena.

A novel membrane-aerated biofilter for the enhanced treatment of nitroaniline wastewater: Nitroaniline biodegradation performance and its influencing factors

Nitroaniline (NA) wastewater is known to be highly toxic and biodegradation-resistant. Based on the principles of molecular oxygen supply and biofilm formation, a novel membrane-aerated biofilter (MABF) combining membrane aeration with a biofilter was established for the first time to treat NA wastewater containing the same concentrations of p-nitroaniline (PNA) and o-nitroaniline (ONA). The NA wastewater treatment performance of the MABF was investigated, and the NA biodegradation characteristics were evaluated. When the influent NA concentration was 120 mg/L, the PNA and ONA removal rates reached 100% and 86.56%, respectively. The NA removal loading reached 111.62 g/m³·d, and the total nitrogen (TN) removal rate reached 82.97%. The synergistic effects of the diverse microorganisms in the membrane-aerated and nonaerated zones of the MABF enhanced the removal of NA and nitrogen. This MABF is an economically efficient and environmentally friendly technology for treating wastewater containing toxic and hazardous organic compounds.

Continuous flow biocatalysis

The continuous flow synthesis of active pharmaceutical ingredients, value-added chemicals, and materials has grown tremendously over the past ten years. This revolution in chemical manufacturing has resulted from innovations in both new methodology and technology. This field, however, has been predominantly focused on synthetic organic chemistry, and the use of biocatalysts in continuous flow systems is only now becoming popular. Although immobilized enzymes and whole cells in batch systems are common, their continuous flow counterparts have grown rapidly over the past two years. With continuous flow systems offering improved mixing, mass transfer, thermal control, pressurized processing, decreased variation, automation, process analytical technology, and in-line purification, the combination of biocatalysis and flow chemistry opens powerful new process windows. This Review explores continuous flow biocatalysts with emphasis on new technology, enzymes, whole cells, co-factor recycling, and immobilization methods for the synthesis of pharmaceuticals, value-added chemicals, and materials.

Manganese and cobalt recovery by surface display of metal binding peptide on various loops of OmpC in Escherichia coli

In a cell-surface display (CSD) system, successful display of a protein or peptide is highly dependent on the anchoring motif and the position of the display in that anchoring motif. In this study, a recombinant bacterial CSD system for manganese (Mn) and cobalt (Co) recovery was developed by employing OmpC as an anchoring motif on three different external loops. A portion of Cap43 protein (TRSRSHTSEG)3 was employed as a manganese and cobalt binding peptide (MCBP), which was fused with OmpC at three different external loops. The fusions were made at the loop 2 [fusion protein-2 (FP2)], loop 6 (FP6), and loop 8 (FP8) of OmpC, respectively. The efficacy of the three recombinant strains in the recovery of Mn and Co was evaluated by varying the concentration of the respective metal. Molecular modeling studies showed that the short trimeric repeats of peptide probably form a secondary structure with OmpC, thereby giving rise to a difference in metal recovery among the three recombinant strains. Among the three recombinant strains, FP6 showed increased metal recovery with both Mn and Co, at 1235.14 (1 mM) and 379.68 (0.2 mM) µmol/g dry cell weight (DCW), respectively.