Sorting the main bottlenecks to use paper-based microbial fuel cells as convenient and practical analytical devices for environmental toxicity testing

Three of the primary bottlenecks, which should be consider for practical, point-of-need use of microbial fuel cell (MFC) analytical devices were surpassed in this work: i) the use of a diffusive barrier, hence, an electrogenic biofllm; ii) longer enrichment/stabilization times to produce a biofllm, made in a laboratory environment, over the electrode; and iii) difficulty comparing results obtained from MFCs based on electrogenic biofllms with standardized bioassays, a setback to be adopted as a new method. Here we show an easy way to determine water toxicity employing planktonic bacteria as biorecognition agents. The paper-based MFC contain an electron carrier (or mediator) to facilitate charge transfer from bacteria to the anode. In this way, there is no need to use biofllms. As far as we know this is the first paper-based MFC containing P. putida KT2440, a well characterized non-pathogenic bacteria previously used in standardized water toxicity bioassays. Results were obtained in 80 min and an effective concentration 50 of 9.02 mg L-1, calculated for Zn2+ (a reference toxic agent), was successfully compared with previously published and ISO standardized bioassays, showing a promising future for this technology. The practical design and cost (less than one U.S. dollar) of the paper-based MFC toxicity test presented will open new market possibilities for rapid and easy-to-use MFC analytical devices. (C) 2020 Elsevier Ltd. All rights reserved.