Microalgae as substrate in low cost terracotta-based microbial fuel cells: Novel application of the catholyte produced.

In this work, the by-product generated during the operation of cylindrical MFCs, made out of terracotta material, is investigated as a feasible means of degrading live microalgae for the first time. In addition to the low cost materials of this design, the reuse of the solution produced in the cathode renders the technology truly green and capable of generating bioenergy. In this study, the effect of a light/dark cycle or dark conditions only on the digestion of live microalgae with the catholyte is investigated. The results show that a combination of light/dark improves degradation and allows algae to be used as substrate in the anode. The addition of 12.5mL of a 1:1 mix of catholyte and microalgae (pre-digested over 5days under light/dark) to the anode, increases the power generation from 7µW to 44µW once all the organic matter in the anode had been depleted.

Stable vesicles composed of monocarboxylic or dicarboxylic fatty acids and trimethylammonium amphiphiles.

The self-assembly of cationic and anionic amphiphile mixtures into vesicles in aqueous media was studied using two different systems: (i) decanoic acid and trimethyldecylammonium bromide and (ii) hexadecanedioic acid (a simple bola-amphiphile) and trimethyldecylammonium bromide. The resulting vesicles with varying amphiphile ratios were characterized using parameters such as the critical vesicle concentration, pH sensitivity, and encapsulation efficiency. We also produced and observed giant vesicles from these mixtures using the electroformation method and confocal microscopy. The mixed catanionic vesicles were shown to be more stable than those formed by pure fatty acids. Those containing bola-amphiphile even showed the encapsulation of a small hydrophilic solute (8-hydroxypyrene-1,3,6-trisulfonic-acid), suggesting a denser packing of the amphiphiles. Compression and kinetics analysis of monolayers composed of these amphiphiles mixtures at the air/water interface suggests that the stabilization of the structures can be attributed to two main interactions between headgroups, predominantly the formation of hydrogen bonds between protonated and deprotonated acids and the additional electrostatic interactions between ammonium and acid headgroups.

Replicability and recurrence in the experimental evolution of a group I ribozyme.

In order to explore the variety of possible responses available to a ribozyme population evolving a novel phenotype, five Tetrahymena thermophila group I intron ribozyme pools were evolved in parallel for cleavage of a DNA oligonucleotide. These ribozyme populations were propagated under identical conditions and characterized when they reached apparent phenotypic plateaus; the populations that reached the highest plateau showed a near 100-fold improvement in DNA cleavage activity. A detailed characterization of the evolved response in these populations reveals at least two distinct phenotypic trajectories emerging as a result of the imposed selection. Not only do these distinct solutions exhibit differential DNA cleavage activity, but they also exhibit a very different correlation with a related, but unselected, phenotype: RNA cleavage activity. In turn, each of these trajectories is underwritten by differing genotypic profiles. This study underscores the complex network of possible trajectories through sequence space available to an evolving population and uncovers the diversity of solutions that result when the process of experimental evolution is repeated multiple times in a simple, engineered system.

Experimental evolution of complexity: in vitro emergence of intermolecular ribozyme interactions.

In the course of evolving variants of the Tetrahymena thermophila Group I ribozyme for improved DNA cleavage in vitro, we witnessed the unexpected emergence of a derived molecular species, capable of acting as a partner for the ribozyme, but no longer autocatalytic. This new RNA species exhibits a deletion in the catalytic core and participates in a productive intermolecular interaction with an active ribozyme, thus insuring its survival in the population. These novel RNA molecules have evolved a precise catalytic interaction with the Group I ribozyme and depend for their survival on the continued presence of active catalysts. This interaction hints at the complexity that may inevitably arise even in simple evolving systems.