A cryogel-based bioreactor for water treatment applications.

The aim of this study was to develop and test a non-diffusion limited, high cell density bioreactor for biodegradation of various phenol derivatives. The bioreactor was obtained using a straightforward one-step preparation method using cryostructuration and direct cross-linking of bacteria into a 3D structured (sponge-like) macroporous cryogel composite material consisting of 11.6% (by mass) cells and 1.2-1.7% polymer, with approximately 87% water (in the material pores). The macroporous cryogel composite material, composed of live bacteria, has pore sizes in the range of 20-150 µm (confirmed by SEM and Laser Scanning Confocal Microscopy). The enzymatic activity of bacteria within the cryogel structure and the effect of freezing on the viability of the cross-linked cells was estimated by MTT assay. Cryogels based on Pseudomonas mendocina, Rhodococcus koreensis and Acinetobacter radioresistens were exploited for the effective bioremediation of phenol and m-cresol, and to a lesser extent 2-chlorophenol and 4-chlorophenol, utilising these phenolic contaminants in water as their only source of carbon. For evaluation of treatment scalability the bioreactors were prepared in plastic "Kaldnes" carriers to improve their mechanical properties and allow application in batch or fluidised bed water treatment modes.

One-step formation of three-dimensional macroporous bacterial sponges as a novel approach for the preparation of bioreactors for bioremediation and green treatment of water.

Immobilisation of bacteria on or into a polymer support is a common method for the utilisation of bacteria as biocatalysts for many biotechnological, medical and environmental applications. The main challenge in this approach is the time taken for the formation of stable biofilms, and the typically low percentage of bacterial cells present on or in the polymer matrix. In this work we propose a novel method for producing a porous bacteria based structure with the properties of a sponge (bacterial sponge) that we then use as a bioreactor for water treatment. Cryogelation has been used as a tool to create macroporous (i.e. with pores in the range 10-100 µm), highly permeable systems with low diffusion constraints and high bacterial content (more than 98% to total material content). A novel crosslinking system was used to form stable bacterial sponges with a high percentage of live bacteria organized in a 3D porous structure. The bacterial sponge was produced in a one step process and can be made from one or several bacterial strains (in this case, two bacterial strains Pseudomonas mendocina and Rhodoccocus koreensis (and a mixture of both) were used). Reduction of the total polymer content to 2% makes the system more sustainable and environmentally friendly under disposal as it can be simply composted. The bacterial sponges have good mechanical stability and cell viability, which enables repeated use of the materials for phenol degradation for up to five weeks. The material can be stored and transported in cryogenic conditions (-80 °C) for prolonged periods of time, retaining its bioremediation activity following 4-6 weeks of frozen storage. The proposed method of producing bioreactors with a high number of live immobilised bacteria, low polymer content and controlled 3D structure is a promising tool for developing novel materials based on active bacterial cells for various environmental, biotechnological, biological and medical applications.

Presence of vancomycin and ampicillin-resistant Enterococcus faecium of epidemic clonal complex-17 in wastewaters from the south coast of England.

The occurrence and diversity of vancomycin-resistant enterococci (VRE) in wastewaters from the Brighton and Hove area of south-east England were investigated. VRE were recovered from 71% of raw urban wastewater samples, 22% of treated urban wastewater samples, 15% of hospital wastewater sample and 33% of farm wastewater samples. Two hundred and eighty-eight isolates were typed and identified and the minimum inhibitory concentrations (MICs) to six antibiotics were determined for selected VRE. Vancomycin-resistant Enterococcus faecium (VREF) strains with a vancomycin MIC of more than 32 mug ml(-1) were examined by polymerase chain reaction for the vanA, vanB and esp genes. Twenty-three VREF with the vanA or vanB gene were further analysed by multilocus sequence typing which revealed that a cluster of VREF from both hospital and urban wastewaters belonged to the high-risk, epidemic, clonal complex-17 (CC17). Vancomycin-resistant Enterococcus faecium belonging to the CC17 group contained the purK-1 allele, were resistant to ampicillin and frequently ciprofloxacin, and usually contained the esp gene. To the authors' knowledge, this is the first report of CC17 strains isolated from urban wastewaters in the UK, and indicates that certain clones carrying antibiotic resistance or virulence traits indicative of the hospital environment can be detected in the urban wastewater system.