Electrochemically assisted bacteria encapsulation in thin hybrid sol–gel films

International audienceA novel method, based on the electrochemical manipulation of the sol-gel process, was developed to immobilize bacteria in thin hybrid sol-gel films. This enabled the safe immobilization of Escherichia coli on electrode surfaces. E. coli strains C600, MG1655 pUCD607 and MG1655 pZNTA-GFP were incorporated and physically encapsulated in a hybrid sol-gel matrix and the metabolic activity and membrane integrity of the bacteria were assessed as a function of the aging time in the absence of nutrients at +4 degrees C or -80 degrees C. LIVE/DEAD BacLight bacterial viability analysis detected by epifluorescence microscopy indicated the preservation of 95% of E. coli C600 membrane integrity in the sol-gel film. The presence of chitosan, trehalose and polyethylene glycol additives was shown to strongly improve the viability of E. coli cells in the electrodeposited matrix for 1 month after encapsulation. Finally, the bioluminescent activity of E. coli MG1655 pUCD607 was preserved by approximately 50% of the cells present in such composite films

Electrochemical analysis of a microbial electrochemical snorkel in laboratory and constructed wetlands

International audienceMicrobial electrochemical snorkel (MES) is a short-circuited microbial fuel cell applicable to water treatment that does not produce energy but requires lower cost for its implementation. Few reports have already described its water treatment capabilities but no deeper electrochemical analysis were yet performed. We tested various materials (iron, stainless steel and porous graphite) and configurations of snorkel in order to better understand the rules that will control in a wetland the mixed potential of this self-powered system. We designed a model snorkel that was studied in laboratory and on the field. We confirmed the development of MES by identifying anodic and cathodic parts, by measuring the current between them and by analyzing microbial ecology in laboratory and field experiments. An important application is denitrification of surface water. Here we discuss the influence of nitrate on its electrochemical response and denitrification performances. Introducing nitrate caused the increase of the mixed potential of MES and of current at a potential value relatively more positive than for nitrate-reducing biocathodes described in the literature. The major criteria for promoting application of MES in artificial wetland dedicated to mitigation of non-point source nitrate pollution from agricultural water are considered