Abstract
Bioremediation is a key process for reclaiming polluted soil and water by the use of biological agents. A commonly used approach aims to neutralise or remove harmful pollutants from contaminated areas using live microorganisms. Generally, immobilised microorganisms rather than planktonic cells have been used in bioremediation methods. Activated carbon, inorganic minerals (clays, metal oxides, zeolites), and agricultural waste products are acceptable substrates for the immobilisation of bacteria, although there are limitations with biomass loading and the issue with leaching of bacteria during the process. Various synthetic and natural polymers with different functional groups have been used successfully for the efficient immobilisation of microorganisms and cells. Promise has been shown using macroporous materials including cryogels with entrapped bacteria or cells in applications for water treatment and biotechnology. A cryogel is a macroporous polymeric gel formed at sub-zero temperatures through a process known as cryogelation. Macroporous hydrogels have been used to make scaffolds or supports for immobilising bacterial, viral, and other cells. The production of composite materials with immobilised cells possessing suitable mechanical and chemical stability, porosity, elasticity, and biocompatibility suggests that these materials are potential candidates for a range of applications within applied microbiology, biotechnology, and research. This review evaluates applications of macroporous cryogels as tools for the bioremediation of contaminants in wastewater.
Highlights
Different cryogel configurations have been developed to immobilise bacteria, including entrapment in a polymeric matrix or attachment to a solid support
Laser Scanning Confocal Microscopy (LSCM) revealed the presence of viable bacteria with the PVA-al and PEI-al crosslinkers, whereas the control material cross-linked with GA contained mostly dead cells
It was shown the potential of cryogels with in situ formed gold nanoparticles to be used for many environmental applications such as the conversion of toxic aromatic nitro derivatives from water and selective adsorption of mercury, via amalgam formation, which can be considered as an efficient water pretreatment stage for following bioremediation processes [44]
Summary
Different cryogel configurations have been developed to immobilise bacteria, including entrapment in a polymeric matrix or attachment to a solid support. The agitation of the reaction mix improves the heat transfer and formation of ice nuclei Cryogels formed this way have large pore volumes and near-uniform porosity with interconnected pores of diameter 20–200 μm, and exhibit twice the strength of cryogels produced by conventional methods Covalent attachment of cells to the support is one of the most widely utilised methods that links the micro-organism with bonding reaction of reactive functionality (amino (–NH2); hydroxyl(–OH)thiol(–SH) or carboxygroups(–COOH)) at the cell’s surface. This leads to the stability of the microorganism, but the bioactivity of bacteria might be slowed down.
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