Carbon felt molecular modification and biofilm augmentation via quorum sensing approach in yeast-based microbial fuel cells

Yeast from the species S. cerevisiae can naturally secrete three quorum sensing (QS) molecules in a certain ratio to regulate metabolism and cellular growth, and to exchange with the surrounding medium. Phenylethanol and tryptophol are considered the predominant QS molecular components with tyrosol being the third. In this work, each of these three QS molecules are separately immobilized, for the first time, onto carbon felt anodes (CF) with polyethyleneimine (PEI) to ascertain the chemical modification of the surface and to enhance the biofilm formation, activity, and conductivity for the direct electron transfer (DET) in yeast-based microbial fuel cells (MFCs). The cyclic voltammetry and electrochemical impedance spectroscopy results suggest that this modification with QS molecules can improve the formation of the biofilm and is very useful for electron transfer mobility. From optical inspection, the biofilm formed inside the felts is relatively more distributed between the fibers, homogenous, and has significant coverage. MFCs adopting CF-PEI/Phenylethanol and CF-PEI/Tryptophol have similar maximum power density (MPD) at 159.46 ± 10.68 mW·m⁻² and 156.57 ± 5.84 mW·m⁻². The yeast biofilm is attached only on the surface of single fibers when tyrosol is immobilized on CF-PEI, which partially explains having the lowest MPD, 135.56 ± 3.79 mW·m⁻². In conclusion, phenylethanol and tryptophol are suggested as the more effective QS molecules whereas tyrosol reduces the absolute amount of sessile biofilm even though the biofilm is still more conductive.