Comparative effect of conductive and dielectric materials on methanogenesis from highly concentrated volatile fatty acids.

Various conductive materials and their dielectric counterparts were used to get deeper insights into contribution of direct interspecies electron transfer (DIET) in improving methanogenesis from highly concentrated volatile fatty acids (12.5 g/L). Potential CH4 yield, maximum CH4 production rate and lag phase were significantly (up to 1.4, 3.9 and 2.0 times, respectively) improved with addition of stainless-steel mesh (SM) and carbon felt (CF) compared to both control and dielectric counterparts (p < 0.05). kapp increased by 82% for SM and 63% for CF compared to control (p < 0.05). Short thick pili-like structures up to 150 nm in width were formed only in CF and SM biofilms, however, were more abundant for SM. Ureibacillus and Limnochordia specific for SM biofilms, and Coprothermobacter and Ca. Caldatribacterium for CF biofilms, were considered electrogenic. Promotion of DIET by conductive materials is governed by many factors, including specificity of electrogenic groups to material surface.

Flow-electrochemical synthesis of Prussian Blue based nanozyme 'artificial peroxidase'.

We report on fully electrochemical flow-through synthesis of Prussian Blue based nanozymes defeating peroxidase in terms of more than 200 times higher catalytic rate constant (k = 6 × 104 s-1). Being reagentless, reproducible, simple and scalable, the proposed approach blazes new trails for the electrosynthesis of functional conductive and electroactive nanomaterials.

Anchoring PQQ-Glucose Dehydrogenase with Electropolymerized Azines for the Most Efficient Bioelectrocatalysis.

Catalytic current of pyrroloquinoline quinone (PQQ)-glucose dehydrogenase (PQQ-GDH) immobilized over electropolymerized methylene green (MG) is increased only five times after the addition of the freely diffusing mediator. This value, being an efficiency criterion for bioelectrocatalysis, is several (three to six) times lower than that for the best reagentless glucose electrodes reported for this enzyme. Thermodynamics of the polyMG|PQQ-GDH electrode is determined by the enzyme-catalyzed reaction pointing to the direct bioelectrocatalysis. PQQ-GDH immobilized over polyMG displays the current plateau region from 0.0 to 0.2 V in the presence of glucose; at 0.00 V, being the optimal potential for biosensing applications, the catalytic current of the polyMG|PQQ-GDH electrode is 700-fold higher than that for the enzyme on a blank electrode. Successful glucose detection in human sweat by means of the corresponding enzyme electrode confirms that the reported bioelectrocatalytic system is attractive for advanced biosensors, as well as for biofuel cells.