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In fuel cells the underlying reactions take place at the catalyst layers composed of materials favoring the desired electrochemical reactions. This paper introduces a formulation process for a catalyst inkjet ink used as an anode for a fully printed flexible fuel cell stack. The optimal ink formulation was 2.5 wt% of carbon–platinum–ruthenium mixture with 0.5% Nafion concentration in a diacetone alcohol solvent vehicle. The best jetting performance was achieved when 1 wt% binder was included in the ink formulation. Anodes with resistivity of approximately 0.1 Ω cm were inkjet printed, which is close to the commercial anode resistivity of 0.05 Ω cm. The anodes were used in fuel cell stacks that were prepared by utilizing only printing methods. The best five-cell-air-breathing stack showed an open circuit potential under H2/air conditions of 3.4 V. The peak power of this stack was 120µW cm−2at 1.75 V, with a resistance obtained from potentiostatic impedance analysis of 295 Ohm cm2. The printed electrodes showed a performance suitable for low-performance solutions, such as powering single-use sensors.

Production of printable enzymatic power sources was scaled up from laboratory to roll-to-roll (R2R) pilot production. The anode and cathode enzymes were glucose oxidase (GOx) and laccase, respectively. The best laboratory-scale cells had a maximum power and energy density of 1.4 ± 0.1 µW cm−2 and 5.5 ± 0.2 µWh cm−2, respectively. These values are 5 and 28 times higher compared to our previously published values. The R2R-produced cells had a maximum power and energy density of 0.40 ± 0.03 µW cm−2 and 0.6 ± 0.1 µWh cm−2, respectively. This is 11 % of the best laboratory manufactured cells. It is suspected that the decrease in electrochemical performance originates from the lower mediator amount and higher drying temperature than that of the laboratory produced cells. However, the trials conducted in this work showed that printed enzymatic active layers can be fabricated and dried with a rotary screen-printing machine in R2R process. Hence, fully printed GOx//laccase power sources could be produced from R2R on a large scale for printed electronics applications.

Printed supercapacitors were prepared to be applied as a part of a hybrid power source in printed electronics applications. The use of non-toxic materials was preferred. The supercapacitor structure consisting of current collectors and activated carbon electrodes was applied on paperboard substrate using silver, graphite and activated carbon inks. Aqueous electrolytes with NaCl salt limit the maximum potential to about 1.2 V but are environmentally friendly and provide low equivalent series resistance (ESR). The capacitance values of our printed supercapacitors were typically 0.1–0.5 F. With 2 cm 2 geometrical active area the ESR was below 1 Ω which is acceptable for 50 mA current output. The efficiency with 50 mA charge and discharge current was typically about 90% and with 10 mA about 95%.

In this work the performance of a printed ThL laccase biocathode is studied utilizing different electrode substrates, compositions and enzyme activities. The results indicate that the performance of the manufactured biocathode can be optimized by selecting a suitable substrate material and increasing the enzyme and mediator loading. By varying the substrate material app. 40 % increase in the cell performance was achieved. In addition by adding ten times higher amount of enzyme and mediator increased the cell performance app. 20 %.

The capability of different fibre preparations to protect the viability and stability of Lactobacillus rhamnosus during freeze-drying, storage in freeze-dried form and after formulation into apple juice and chocolate-coated breakfast cereals was studied. In freeze-drying trials wheat dextrin and polydextrose proved to be promising carriers for the L. rhamnosus strains: both freeze-drying survival and storage stability at 37 °C were comparable to the control carrier (sucrose). Using apple fibre and inulin carriers resulted in powders with fairly good initial freeze-drying survival but with poor storage stability at 37 °C. When fresh L. rhamnosus cells were added into apple juice (pH 3.5) together with oat flour with 20% β-glucan the survival of the cells was much better at 4 °C and at 20 °C than with sucrose, wheat dextrin and polydextrose, whereas with freeze-dried cells no protective effect of oat flour could be seen. The stability of freeze-dried L. rhamnosus cells at 20 °C was higher in chocolate-coated breakfast cereals compared to low pH apple juice. Similar to freeze-drying stability, wheat dextrin and polydextrose proved to be better carriers than oat flour in chocolate-coated breakfast cereals. Regardless of their differing capability to adhere to fibre preparations the two L. rhamnosus strains studied gave parallel results in the stability studies with different carriers.

Due to its technological feasibility, Bifidobacterium animalis subsp. lactis is the most widely used Bifidobacterium species in probiotic applications. Fermenter-scale growth of B. animalis subsp. lactis in GEM (a medium supporting well the growth of bifidobacteria) followed by freeze-drying produced preparations with good storage stability. However, a decrease in the acid tolerance of preparations was observed during the storage at elevated temperatures. Pepsin protected the cells during an exposure to low pH. Addition of pepstatin A (pepsin inhibitor) or N,N′-dicyclohexylcarbodiimide (DCCD; an inhibitor of proton translocating enzymes) decreased the protective ability at pH 2.0, while heat treatment did not have an influence on it. Measurement of membrane potential changes (DiBAC4(3)) showed that pepsin decreased hyperpolarization of the cells during an exposure to low pH suggesting that the protective ability is linked to the H+-ATPase activity of the cells. Our findings indicate a need for assessing parameters related to cell functionality in addition to culture-based stability of probiotic preparations.

Bacterial strains were isolated from spruce wood chips and their ability to reduce the content of wood extractives was studied. Strains were screened by cultivation on liquid media containing wood extractives as the major nutrient. Some bacterial species could decrease remarkably the amount of extractives in the liquid media and reduced the amount of triglycerides, steryl esters and total extractives by 100, 20 and 39%, respectively. Spruce wood chips were treated in controlled conditions with selected bacteria to test their effects on the chips. All the bacteria grew well on wood chips. The effect of bacterial metabolism on wood extractives was significant. Bacterial treatments reduced the amount of lipophilic extractives by 16-38% in 1 week of treatment and up to 67% in 2 weeks. The most efficient strain removed 90, 66 and 50% of triglycerides, steryl esters and resin acids, respectively, in 2 weeks. These results indicate that bacteria may be promising agents for the removal of extractives for improved pulping and papermaking processes.

Current generation by mediated enzyme electron transfer at electrode surfaces can be harnessed to provide biosensors and redox reactions in enzymatic fuel cells. A glucose/oxygen enzymatic fuel cell can provide power for portable and implantable electronic devices. High volume production of enzymatic fuel cell prototypes will likely require printing of electrode and catalytic materials. Here we report on preparation and performance of, completely enzymatic, printed glucose/oxygen biofuel cells. The cells are based on filter paper coated with conducting carbon inks, enzyme and mediator. A comparison of cell performance using a range of mediators for either glucose oxidase (GOx) or aldose dehydrogenase (ALDH) oxidation of glucose at the anode and ABTS and a fungal laccase, for reduction of oxygen at the cathode, is reported. Highest power output, although of limited stability, is observed for ALDH anodes mediated by an osmium complex, providing a maximum power density of 3.5 μW cm(-2) at 0.34 V, when coupled to a laccase/ABTS cathode. The stability of cell voltage in a biobattery format, above a threshold of 200 mV under a moderate 75 kΩ load, is used to benchmark printed fuel cell performance. Highest stability is obtained for printed fuel cells using ALDH, providing cell voltages over the threshold for up to 74 h, compared to only 2 h for cells with anodes using GOx. These results provide promising directions for further development of mass-producible, completely enzymatic, printed biofuel cells.

Enzyme electrodes show great potential for many applications, as biosensors and more recently as anodes and cathodes in biocatalytic fuel cells for power generation. Enzymes have advantages over metal catalysts, as they provide high specificity and reaction rates, while operating under mild conditions. Here we report on studies related to development of mass-producible, completely enzymatic printed glucose/oxygen biofuel cells. The cells are based on filter paper coated with conducting carbon inks containing mediators and laccase, for reduction of oxygen, or aldose dehydrogenase, for oxidation of glucose. Mediator performance in these printed formats is compared to relative rate constants for the enzyme–mediator reaction in solution, for a range of anode and cathode mediators. The power output and stability of fuels cells using an acidophilic laccase isolated from Trametes hirsuta is greater, at pH 5, than that for cells based on Melanocarpus albomyces laccase, that shows optimal activity closer to neutral pH, at pH 6. Highest power output, although of limited stability, was observed for ThL/ABTS cathodes, providing a maximum power density of 3.5 μW cm−2 at 0.34 V, when coupled to an ALDH glucose anode mediated by an osmium complex. The stability of cell voltage above a threshold of 200 mV under a moderate 75 kΩ load is used to benchmark printed fuel cell performance. Highest stability was obtained for a printed fuel cell using osmium complexes as mediators of glucose oxidation by aldose dehydrogenase, and oxygen reduction by T. hirsuta laccase, maintaining cell voltage above 200 mV for 137 h at pH 5. These results provide promising directions for further development of mass-producible, completely enzymatic, printed biofuel cells.

Low cost printable power sources are needed e.g. in sensors and RFID applications. As manufacturing method printing techniques are preferred in order to keep the costs low. The materials should also be easily disposable. Enzymatic bio-fuel cells are an alternative for printable primary batteries. Since one drawback of bio-fuel cells is their low power, we have developed supercapacitors that can be combined with enzymatic bio-fuel cells to provide the power peaks necessary in the applications. The materials for the supercapacitors have been chosen to be compatible with the fuel cell and with printing methods, e.g. the activated carbon powder in the electrodes was bound with chitosan. As printing substrates we have used paperboards. The current collectors have been made of graphite and metal inks. Since the voltage requirement is limited to approximately 1 V, aqueous electrolytes have been used. Printed supercapacitors of various sizes have been prepared. The geometrical electrode areas have been between 0.5 and 2 cm2. The maximum feasible output current has been in the order of 50 mA corresponding to about 50 mW power. When the capacitor is used together with an enzymatic power source, the leakage current must be as low as possible. Typical leakage current values have been in the order of 10 µA.

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A multilayered structure suitable as an electrode in a power source and a method of producing the same. The structure comprises a conductive laminar layer; and an enzyme layer containing an essentially dry enzyme capable of oxidizing or dehydrogenating carbohydrate material under suitable conditions. Because the enzymatic anode layer and the fuel containing layer are not interacting during the production and since they are kept latent during storage time, the power source will remain stable for extended periods of time, thus increasing the utility of the power source.Patent family as of 15.9.2021DE602010050092 D1 20180517 DE201060050092T 20101216 EP2514017 A1 20121024 EP20100837114 20101216 EP2514017 A4 20141224 EP20100837114 20101216 EP2514017 B1 20180418 EP20100837114 20101216 ES2675121 T3 20180706 ES20100837114T 20101216 FI122265 B 20111115 FI20090006338 20091216 FI20096338 A 20110617 FI20090006338 20091216 FI20096338 A0 20091216 FI20090006338 20091216 US2013017457 AA 20130117 US20100516332 20101216 US9614243 BB 20170404 US20100516332 20101216 WO11073530 A1 20110623 WO2010FI51048 20101216Link to current patent family on right

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In Denmark, the wet-oxidation (WO) process has been used for fractionating wheat straw [10], where most of the hemicellulose is solubilised mainly as oligomers and polymers and the cellulose retained as a solid. In wheat straw, hemicellulose is an arabino-4-O-methylglucurono xylan, which, in addition to xylose, contains arabinose, 4-O-Me-D-glucuronic acid, and acetic acid substituents [9]. Some arabinosyl groups may be esterified with ferulic or p-coumaric acids. Most micro-organisms used for lactate, ethanol or xylitol production do not produce enzymes for hemicellulose hydrolysis. Acid or enzymatic hydrolysis is needed to convert the sugar polymers to monomers. A problem associated with dilute acid hydrolysis is the poor fermentability of the produced hydrolysates compared with enzymatic hydrolysis. This study investigated the utilisation of wet-oxidised wheat straw xylan (WO-xylan) for production of enzymes for hydrolysis. Three fungal strains (Aspergillus oryzae, Aspergillus fumigatus, and Trichoderma reesei) were cultivated on WO-xylan using xylan (Lenzig AG) as a supplementary carbon-source. A. oryzae was selected for production of enzymes in larger scale.