Bacteria and viruses were encapsulated in electrospun polymer nanofibres. The bacteria and viruses were suspended in a solution of poly(vinyl alcohol) (PVA) in water and subjected to an electrostatic field of the order of 1 kV cm(-1). Encapsulated bacteria in this work, (Escherichia coli, Staphylococcus albus) and bacterial viruses (T7, T4, λ) managed to survive the electrospinning process while maintaining their viability at fairly high levels. Subsequently the bacteria and viruses remain viable during three months at -20 and -55 °C without a further decrease in number. The present results demonstrate the potential of the electrospinning process for the encapsulation and immobilization of living biological material.

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Encapsulation of whole microbial cells in microtubes for use in bioremediation of pollutants in water systems was the main focus of this investigation. Coelectrospinning of a core polymeric solution with bacterial cells and a shell polymer solution using a spinneret with two coaxial capillaries resulted in microtubes with porous walls. The ability of the microtube's structure to support cell attachment and maintain enzymatic activity and proliferation of the encapsulated microbial cells was examined. The results obtained show that the encapsulated cells maintain some of their phosphatase, β-galactosidase and denirification activity and are able to respond to conditions that induce these activities. This study demonstrates electrospun microtubes are a suitable platform for the immobilization of intact microbial cells.

Enzymes were directly encapsulated in microtubes fabricated by coelectrospinning. Coelectrospinning makes it possible to separate between an organic phase, which may be harmful to enzyme activity, and an aqueous one. In this report, enzymes were incorporated in an aqueous core solution of poly(ethylene oxide) (PEO) while the shell solution was made of polycaprolactone (PCL) dissolved in a mixture of chloroform and dimethylformamide (DMF). Indeed, this separation was found to preserve the enzymatic activities of two enzymes during and after electrospinning, as ascertained when the fiber mats were placed in an aqueous assay environment. The shell morphology was altered by blending PCL with poly(ethylene glycol) (PEG). This blending induced pores in the shell which in turn pronouncedly affected the movement of molecules into or out of the fibers. An enzyme of about 80 kDa, alkaline phosphatase (AP), diffused through the pores into the surrounding medium. The fibers can thus act as release devices. However, a larger enzyme, β-galactosidase (465 kDa), remained in the fibers without any leaching. Enzyme assays showed that the substrates of both enzymes diffused efficiently into the fibers and were cleaved by the encapsulated enzyme, and the reaction product then diffused outside. With encapsulated β-galactosidase, the fiber acted as an efficient enzymatic microreactor and the relative enzymatic activity reached a level of about 50%.

Luminescence in the marine bacterium, Vibrio fischeri, is regulated by a small molecule, the autoinducer. The transcription of the V. fischeri lux genes also requires a regulatory protein, (luxR), cAMP and CRP. We show that, apart from these components, the transcription of the PR lux operon is also controlled by the activity of sigma 32 (htpR protein). In luminescent Escherichia coli (E. coli/pChv1), as well as in different marine luminous bacteria and their naturally occurring dark (K) variants, the luminescence system can be induced by starvation under microaerophilic conditions. Heat shock also induces luminescence in htpR+ but not in htpR- strains of E. coli/pChv1. An htpR- mutant of E. coli containing pChv1 is very dim and its luminescence is not induced by starvation or heat shock. The addition of a plasmid bearing the gene for htpR+ into such cells restores their response to starvation and heat shock. Cells of wild type E. coli/pChv1 that have been starved or heat shocked respond to lower concentrations of V. fischeri inducer than untreated cells. These cultures also produce more extracellular inducer than untreated cells. Starvation, heat shock and the presence of sigma 32 do not induce luminescence in luxl deleted E. coli/pChv1 cells. SOS-inducing agents advance the onset of luminescence in both htpR+ and htpR- strains but not in luxl deleted E. coli/pChvi cells. DNA sequencing of the luxR-luxl region reveals the presence of a promoter region of the kind typical for sigma 32 at the beginning of the luxl gene. In addition we find a LexA protein-DNA binding site in the non-consensus sequence for the -35 region of the PR operon. It is proposed that the regulatory protein-inducer complex displaces the LexA protein and allows the transcription of the right operon. SOS-inducing agents result in proteolysis of LexA protein and advance the onset of luminescence. sigma 32 enhances the transcription from the PR operon and thus initiates a positive control circuit. It seems that sigma 32 is the major controlling element in determining the onset of luminescence both in vivo and in vitro.