Biodiesel via in situ wet microalgae biotransformation: Zwitter-type ionic liquid supported extraction and transesterification

The production of biodiesel derived from microalgae is among the most forthcoming technologies that provide an ecologic alternative to fossil fuels. Herein, a method was developed that enables the direct extraction and conversion of algal oil to biodiesel without prior isolation. The reaction occurs in aqueous media catalyzed by immobilized Candida antarctica lipase B (Novozyme 435). Zwitter-type ionic liquids were used as cocatalyst to improve the selectivity and reactivity of the enzyme. In a model reaction with sunflower oil, 64% biodiesel was obtained. Applying this method to a slurry of whole-cell Chlorella zof ingiensis in water resulted in 74.8% of lipid extraction, with 27.7% biotransformation products and up to 16% biodiesel. Factors that reduced the lipase activity with whole-cell algae were subsequently probed and discussed. This "in situ" method shows an improvement to existing methods, since it integrates the oil extraction and conversion into an one-pot procedure in aqueous conditions. The extraction is nondisruptive, and is a model for a greener algae to biodiesel process

Biofilm vivacity and destruction on antimicrobial nanosurfaces assayed within a microbial fuel cell

A novel method was developed to assay the antimicrobial capacity of nanostructured surfaces for medical implants in a bicathodic microbial fuel cell. Nano-structured gold surfaces with protruding nanopillars and nanorings were investigated. Escherichia coli K12 were used as a model microbe to record electronic effects caused by the interaction with nanosurfaces. The nanostructured gold surfaces enabled power density maxima up to 1910 mW/m2, indicating fair vivacity, while flat surfaces on the nanoscale provided almost no power 0.35 mW/m2. The biofilm presence on antimicrobial nanosurfaces was confirmed by the addition of ampicillin and its bactericidal effect resulted in oscillating and declining potentiometric signals. Current density experiments showed that biofilms on antimicrobial nanostructured electrodes caused low currents, indicating that E.coli biofilm remained functional before destruction. The bicathodic microbial fuel cell sensor is a novel tool for evaluating antimicrobial effects caused by nanosurfaces and antibiotics

Microbial electrolysis cell accelerates phosphate remobilisation from iron phosphate contained in sewage sludge

Phosphate was remobilised from iron phosphate contained in digested sewage sludge using a bio-electric cell. A significant acceleration above former results was caused by strongly basic catholytes. For these experiments a dual chambered microbial electrolysis cell with a small cathode (40 mL) and an 80 times larger anode (2.5 L) was equipped with a platinum sputtered reticulated vitreous carbon cathode. Various applied voltages (0.2–6.0 V) generated moderate to strongly basic catholytes using artificial waste water with pH close to neutral. Phosphate from iron phosphate contained in digested sewage sludge was remobilised most effectively at pH ∼13 with up to 95% yield. Beside minor electrochemical reduction, hydroxyl substitution was the dominating remobilisation mechanism. Particle–fluid kinetics using the “shrinking core” model allowed us to determine the reaction controlling step. Reaction rates changed with temperature (15–40 °C) and an activation energy of Ea = 55 kJ mol−1 was found. These analyses indicated chemical and physical reaction control, which is of interest for future scale-up work. Phosphate remobilisation rates increased significantly, yields doubled and recovered PO43− concentrations increased four times using a task specific bio-electric system. The result is a sustainable process for decentralized phosphate mining and a green chemical base generator useful also for many other sustainable processing needs

Microbial fuel cell stack power to lithium battery stack ::pilot concept forscale up

A stack to stack microbial fuel cell power to batteries storage was investigated on the pilot scale with the aim to scale up in future. A 12 unit MFC-stack, equipped with maximum power point tracking (MPPT) and lithium polymer batteries (3.7 V), was set up. The MFC-stack architecture was simplified by sharing partially electrolytes. The serial 12 unit MFC-stack was first used as a linear assembly of all MFC units and then subdivided into three MFC-sub-stacks which enhanced power extraction by 8.5 times. To balance the stack power generation, the external circuits were alternated into zigzag, braid and random figurations as well in rational directed configurations. Finally, batteries permutation along with MPPT enabled faster and balanced lithium battery stack charging. Balanced conditions resulted in time shift oscillations, the absence of unwanted power pooling and voltage reversals. All in all, the work showed how to generate and store power from an 12 L microbial fuel cell stack with partly common electrolytes

Modeling of sustainable base production by microbial electrolysis cell

A predictive model for the microbial/electrochemical base formation from wastewater was established and compared to experimental conditions within a microbial electrolysis cell. A Na2SO4/K2SO4 anolyte showed that model prediction matched experimental results. Using Shewanella oneidensis MR-1, a strong base (pH≈13) was generated using applied voltages between 0.3 and 1.1 V. Due to the use of bicarbonate, the pH value in the anolyte remained unchanged, which is required to maintain microbial activity

Probing electron transfer with Escherichia coli ::a method to examine exoelectronics in microbial fuel cell type systems

Escherichia coli require mediators or composite anodes for substantial outward electron transfer, >8 A/m2. To what extent non-mediated direct electron transfer from the outer cell envelope to the anode occurs with E. coli is a debated issue. To this end, the redox behaviour of non-exoelectrogenic E. coli K12 was investigated using a bi-cathodic microbial fuel cell. The electromotive force caused by E. coli biofilms mounted 0.2–0.3 V above the value with the surrounding medium. Surprisingly, biofilms that started forming at different times synchronised their EMF even when physically separated. Non-mediated electron transfer from E. coli biofilms increased above background currents passing through the cultivation medium. In some instances, currents were rather high because of a sudden discharge of the medium constituents. Mediated conditions provided similar but more pronounced effects. The combined step-by-step method used allowed a systematic analysis of exoelectronics as encountered in microbial fuel cells

Biodiesel via in situ wet microalgae biotransformation ::zwitter-type ionic liquid supported extraction and transesterification

The production of biodiesel derived from microalgae is among the most forthcoming technologies that provide an ecologic alternative to fossil fuels. Herein, a method was developed that enables the direct extraction and conversion of algal oil to biodiesel without prior isolation. The reaction occurs in aqueous media catalyzed by immobilized Candida antarctica lipase B (Novozyme 435). Zwitter-type ionic liquids were used as cocatalyst to improve the selectivity and reactivity of the enzyme. In a model reaction with sunflower oil, 64% biodiesel was obtained. Applying this method to a slurry of whole-cell Chlorella zofingiensis in water resulted in 74.8% of lipid extraction, with 27.7% biotransformation products and up to 16% biodiesel. Factors that reduced the lipase activity with whole-cell algae were subsequently probed and discussed. This “in situ” method shows an improvement to existing methods, since it integrates the oil extraction and conversion into an one-pot procedure in aqueous conditions. The extraction is nondisruptive, and is a model for a greener algae to biodiesel process

Cathode deposits favor methane generation in microbial electrolysis cell

Cathodes in microbial electrolysis cells are exposed to poisoning in particular when using activated sludge as substrate. In this work, it was examined how well hydrogen generation is possible and what kind of membrane protection is sufficient to produce hydrogen from activated sludge. Also model microbial electrolysis was performed to simulate hydrogen evolution in a mimic biological environment at pH = 7. With activated sludge, it was found that electrodeposition of calcium, iron and phosphor and other impurities inhibited the hydrogen evolution reaction. Applying 2.0 V, the biogas productivity increased notably as if it induced rather chemical hydrolysis than hydrogenation and favored methanisation. This MEC generated methane in up to highest purity, 67–97%. In addition, this room-temperature methanisation consumed far less energy than with comparable mesophile conditions

Two stage bioethanol refining with multi litre stacked microbial fuel cell and microbial electrolysis cell

Ethanol, electricity, hydrogen and methane were produced in a two stage bioethanol refinery setup based on a 10 L microbial fuel cell (MFC) and a 33 L microbial electrolysis cell (MEC). The MFC was a triple stack for ethanol and electricity co-generation. The stack configuration produced more ethanol with faster glucose consumption the higher the stack potential. Under electrolytic conditions ethanol productivity outperformed standard conditions and reached 96.3% of the theoretically best case. At lower external loads currents and working potentials oscillated in a self-synchronized manner over all three MFC units in the stack. In the second refining stage, fermentation waste was converted into methane, using the scale up MEC stack. The bioelectric methanisation reached 91% efficiency at room temperature with an applied voltage of 1.5 V using nickel cathodes. The two stage bioethanol refining process employing bioelectrochemical reactors produces more energy vectors than is possible with today’s ethanol distilleries

Scale-up of phosphate remobilization from sewage sludge in a microbial fuel cell

Phosphate remobilization from digested sewage sludge containing iron phosphate was scaled-up in a microbial fuel cell (MFC). A 3 litre triple chambered MFC was constructed. This reactor was operated as a microbial fuel cell and later as a microbial electrolysis cell to accelerate cathodic phosphate remobilization. Applying an additional voltage and exceeding native MFC power accelerated chemical base formation and the related phosphate remobilization rate. The electrolysis approach was extended using a platinum-RVC cathode. The pH rose to 12.6 and phosphate was recovered by 67% in 26 h. This was significantly faster than using microbial fuel cell conditions. Shrinking core modelling particle fluid kinetics showed that the reaction resistance has to move inside the sewage sludge particle for considerable rate enhancement. Remobilized phosphate was subsequently precipitated as struvite and inductively coupled plasma mass spectrometry indicated low levels of cadmium, lead, and other metals as required by law for recycling fertilizers. (C) 2015 Elsevier Ltd. All rights reserved