Although microbes have been used in industrial and niche applications for several decades, successful immobilization of microbes while maintaining their usefulness for any desired application has been elusive. Such a functionally bioactive system has distinct advantages over conventional batch and continuous-flow microbial reactor systems that are used in various biotechnological processes. This article describes the use of polyethylene oxide 99-polypropylene oxide 67-polyethylene oxide99 triblock polymer fibers, created via electrospinning, to encapsulate microbes of 3 industrially relevant genera, namely, Pseudomonas, Zymomonas, and Escherichia. The presence of bacteria inside the fibers was confirmed by fluorescence microscopy and SEM. Although the electrospinning process typically uses harsh organic solvents and extreme conditions that generally are harmful to bacteria, we describe techniques that overcome these limitations. The encapsulated microbes were viable for several months, and their metabolic activity was not affected by immobilization; thus they could be used in various applications. Furthermore, we have engineered a microbe-encapsulated cross-linked fibrous polymeric material that is insoluble. Also, the microbe-encapsulated active matrix permits efficient exchange of nutrients and metabolic products between the microorganism and the environment. The present results demonstrate the potential of the electrospinning technique for the encapsulation and immobilization of bacteria in the form of a synthetic biofilm, while retaining their metabolic activity. This study has wide-ranging implications in the engineering and use of novel bio-hybrid materials or biological thin-film catalysts.biofilm ͉ cross-linking ͉ immobilization ͉ microbial ͉ Zymomonas

Multiblock copolymers of poly(ethylene oxide) 99 -poly(propylene oxide) 67 -poly(ethylene oxide) 99 (F127) were synthesized by chain extending with hexamethylene diisocyanate (HDI). The resulting multiblock copolymer poly-F127 maintained the thermoreversible properties of the original F127 triblock copolymer. The rheological and structural properties of the gels were characterized as a function of temperature, composition and degree of polymerization. Neutron scattering reveals that a large degree of alignment can be induced in the F127 gel, but no long-range order could be found in the multiblocks or the mixtures of F127 with multiblocks. The shear strain at yield in polymers having an average of 3.2 or more F127 repeats was nearly an order of magnitude higher than in the F127 gel. For F127 solutions just below their gel point, substitution of F127 with as little as 1% multiblock succeeded in forming a physical gel. Percolation theory was used to understand the modulus growth when multiblock was added to F127 solutions just below their gel point, assuming the multiblocks form bridges between adjacent micelles.

The hypothesis that chain extension can be harnessed to the generation of improved reverse thermo‐responsive polymers was tested by following two basic synthetic pathways: (1) the polymerization of poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) (PEO‐PPO‐PEO) triblocks using hexamethylene diisocyanate (HDI) as chain extender and (2) the covalent binding of poly(ethylene glycol) and poly(propylene glycol) chains, using phosgene as the connecting molecule. While in the former, the basic amphiphilic repeating unit is known for its own RTG behavior, the latter polymers consist of segments incapable of exhibiting a reverse thermal gelation (RTG) of their own. Dynamic light scattering (DLS) measurements revealed that the nanostructures formed by the chain extended polymers were markedly larger than those generated by PEO‐PPO‐PEO triblocks. While the size of Pluronic F127 micelles ranged from 15 to 20 nm, the higher molecular weight amphiphiles generated much larger nanostructures (20–400 nm). The chain extended polymers achieved much higher viscosities and their gels displayed enhanced long‐term stability at 37°C. Copyright © 2007 John Wiley & Sons, Ltd.