Bioencapsulation has been a promising technique for various biotechnological and medical applications. Nevertheless, when encapsulated, the activity of the encapsulated biologicals is usually reduced due to diffusional resistance and use of organic solvents in the process. Here, we developed a sal-gel electrospinning technique to encapsulate a bacterium, Escherichia coli expressing a biocatalyst, AtzA, into hybrid silica/polyvinyl alcohol nanofibers. We used a microfluidic timer to maintain a constant sal viscosity, thus enabling continuous formation of silica gel nanofibers weaving a bioreactive mat. Encapsulation of bacteria into thin-walled (a few tens of nanometers) fibers significantly reduced diffusional resistance. Furthermore, with this process, the need for organic solvents was eliminated. This enabled us to reach encapsulated bacteria activity at the levels seen in free cells. This novel process enables new large-scale applications in biotechnology, especially in bioremediation, biosensors, and manufacturing of recombinant proteins. (C) 2013 Elsevier B.V. All rights reserved.