Using an in-house developed platform, the performance of an Arthrospira maxima biofilm photosynthetic microbial fuel cell (PMFC) was monitored both optically and electrochemically. Fluorescence (excitation wavelength 633 nm, emission range 640 to 800 nm for detection of fluorescence), power density and current output of the PMFC were recorded in real time. Confocal microscopy performed in situ allowed detailed fluorescence imaging to further improve the understanding of the photosynthetic activity of the biofilm that developed on the anode surface of the PMFC, whilst power and current outputs indicated the performance of the cell. The PMFC was shown to be sensitive to temperature and light perturbations with increased temperatures and light intensities resulting in improved performance. A direct relationship between the fluorescent signature and the amount of current produced was identified. With a decreasing external load and increasing current production, the biofilm attached to the anode electrode showed increased fluorescence inferring improved activity of the photosynthetic material. Furthermore, the imaging proved that viable cells covered the entire surface area of the biofilm and that the fluorescence increased with increasing distance (z axis) from the electrode surface.
Anaerobic digestion (AD) is a unit process that integrates beneficially and sustainably into many bioprocesses. This study assesses and compares the production of methane from the biomass of the microalga Scenedesmus sp. and the cyanobacterium Spirulina sp. in batch anaerobic digesters. Anaerobic digestion of whole cell Spirulina resulted in a substantially higher methane productivity (0.18 L CH4.Lreactor-1 .day-1) and methane yield (0.113 L CH4.g-1 volatile solids (VS)) compared to the digestion of whole cell Scenedesmus (0.12 L CH4.Lreactor-1 .day-1 and 0.054 L CH4.g VS-1). Spirulina, possibly due to a combination of osmotic shock, the filamentous nature of the cells and lower mechanical strength of the noncellulosic cell wall, was more readily degraded by hydrolytic and acidogenic microorganisms, resulting in the generation of a greater amount of acetic acid. This in turn provided greater substrate for methanogens and hence higher methane yields. In addition, Spirulina cells could be disrupted mechanically more quickly (1h) than Scenedesmus cells (4h) in a bead mill. Mechanical pre-treatment improved the final methane yields (L CH4.g VS-1) obtained from digestion of both substrates, however, the improvement was greater for Scenedesmus. Mechanical pre-treatment resulted in a 47% increase in methane production for Spirulina compared to 76% increase for Scenedesmus fed digesters. The more substantial increase observed for Scenedesmus was due to the relatively inefficient digestion of the whole, unruptured cells.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.