Durable electrospun microtubes for encapsulation of bacteria in atrazine bioremediation

The operation of classic biological reactors under starvation conditions is ineffective due to bacterial washout and detachment. In this paper, an innovative approach to maintaining high cell concentrations in a continuous reactor under starvation conditions based on electrospun encapsulation is investigated. Pseudomonas sp. strain ADP (P. ADP) bacteria was encapsulated in core-shell electrospun microtubes and used as coverings on plastic carriers for bioremediation of atrazine without adding an external electron donor to minimise pollution. A microtube formulation consisting of polyvinylpyrrolidone (PVP) as the core solution and polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) as the shell material was investigated for the encapsulation of bacteria. Encapsulated P. ADP bacteria showed an initial inhibition to atrazine degradation mainly due to stress from electrospinning or solvents left over in the microtubes. However, atrazine degradation activity was regained after a number of consecutive batches. Microtubes containing bacteria were wrapped on plastic carriers, placed in a reactor and operated continuously without an external carbon source for 50 days. Good atrazine degradation (83.1 +/- 3.9%) and ammonium recovery (75.5 +/- 5.9%) were observed in the reactor. Carrier samples taken at the end of the experiment showed no significant microtube deterioration, although biofilm growth appeared on the external surface of the microtubes due to the prevailing non-sterile conditions. The results show the potential for the application of this method in bioreactors.