The pollution caused by heavy metals (HMs) represents a global concern due to their serious environmental threat. Photosynthetic cyanobacteria have a natural niche and the ability to remediate HMs such as cadmium. However, their practical application is hindered by a low tolerance to HMs and issues related to recycling. In response to these challenges, this study focuses on the development and evaluation of engineered cyanobacteria-based living materials for HMs bioremediation. Genes encoding phytochelatins (PCSs) and metallothioneins (MTs) were introduced into the model cyanobacterium Synechocystis sp. PCC 6803, creating PM/6803. The strain exhibited improved tolerance to multiple HMs and effectively removed a combination of Cd2+, Zn2+, and Cu2+. Using Cd2+ as a representative, PM/6803 achieved a bioremediation rate of approximately 21 μg of Cd2+/OD750 under the given test conditions. To facilitate its controllable application, PM/6803 was encapsulated using sodium alginate-based hydrogels (PM/6803@SA) to create “living materials” with different shapes. This system was feasible, biocompatible, and effective for removing Cd2+ under simulated conditions of zebrafish and mice models. Briefly, in vitro application of PM/6803@SA efficiently rescued zebrafish from polluted water containing Cd2+, while in vivo use of PM/6803@SA significantly decreased the Cd2+ content in mice bodies and restored their active behavior. The study offers feasible strategies for HMs bioremediation using the interesting biomaterials of engineered cyanobacteria both in vitro and in vivo.
Bo Caiying,Hu Lihong,Chen Yong,Yang Xiaohui,Zhang Meng,Zhou Yonghong
A novel phosphorus-containing cardanol (PCC) derived from cardanol—a renewable meta -substituted phenol and harmful by-product of the cashew industry—in combination with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was used to produce bio-based phenolic foams (PFs). The properties of the PFs were then characterized in detail. The PCC was fully characterized by using Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance ( 1 H NMR), while the thermal degradation was studied and monitored by thermogravimetry coupled to FTIR (TGA/FTIR) and TGA coupled with mass spectrometry (TGA/MS). It was found that PCC exhibited high thermal stability. The total heat release, peak heat release rate and mean heat release rate of PF containing 4% PCC decreased by 13.55, 33.43 and 13.42%, respectively, in comparison with pristine PF. The enhanced flame-retardant behavior was attributed to the free radicals PO· produced during combustion, which captured free radicals in the gas phase; moreover, the phosphaphenanthrene group may create a char residue barrier against the further combustion of the polymer. Meanwhile, bio-based PFs showed excellent mechanical properties, as the compressive and flexural strength of PF with 4% PCC increased by 79.59 and 20.98%, respectively, in comparison with pristine PF. The pulverization ratio of bio-based PFs was reduced with the increase in PCC content. The findings in this study demonstrate that PCC could be used as a phenol substitute in the synthesis of PFs to overcome their intrinsic brittleness and high flammability.
危险品化学品经营许可证（带存储）