Facile preparation of flame-retardant cellulose composite with biodegradable and water resistant properties for electronic device applications.

The aim of the present study is to produce flexible, flame-retardant, water-resistant and biodegradable composite materials. The ultimate goal of this research is to develop simple processes for the production of bio-based materials capable of replacing non-degradable substrates in printed circuit board. Cellulose was chosen as a renewable resource, and dissolved in 1-ethyl-3-methylimidazolium acetate ionic liquid to prepare a cellulosic continuous film. Since flame retardancy is an important criterion for electronic device applications and cellulose is naturally flammable, we incorporated ammonium polyphosphate (APP) as a flame-retardant filler to increase the flame retardancy of the produced materials. The developed material achieved a UL-94 HB rating in the flammability test, while the cellulose sample without APP failed the test. Two hydrophobic agents, ethyl 2-cyanoacrylate and trichloro(octadecyl)silane were applied by a simple dip-coating technique to impart hydrophobicity to the cellulose-APP composites. Dynamic mechanical analysis indicated that the mechanical properties of the cellulosic materials were not significantly affected by the addition of APP or the hydrophobic agents. Moreover, the biodegradability of the cellulosic materials containing APP increased owing to the presence of the cellulase enzyme. The hydrophobic coating slightly decreased the biodegradability of cellulose-APP, but it was still higher than that of pure cellulose film.

Influence of Calcium Silicate and Hydrophobic Agent Coatings on Thermal, Water Barrier, Mechanical and Biodegradation Properties of Cellulose.

Thin films of cellulose and cellulose-CaSiO3 composites were prepared using 1-ethyl-3-methylimidazolium acetate (EMIMAc) as the dissolution medium and the composites were regenerated from an anti-solvent. The surface hydrophilicity of the resultant cellulose composites was lowered by coating them with three different hydrophobizing agents, specifically, trichloro(octadecyl)silane (TOS), ethyl 2-cyanoacrylate (E2CA) and octadecylphosphonic acid (ODPA), using a simple dip-coating technique. The prepared materials were subjected to flame retardancy, water barrier, thermal, mechanical and biodegradation properties analyses. The addition of CaSiO3 into the cellulose increased the degradation temperature and flame retardant properties of the cellulose. The water barrier property of cellulose-CaSiO3 composites under long term water exposure completely depends on the nature of the hydrophobic agents used for the surface modification process. All of the cellulose composites behaved mechanically as a pure elastic material with a glassy state from room temperature to 250 °C, and from 20% to 70% relative humidity (RH). The presence of the CaSiO3 filler had no effect on the elastic modulus, but it seemed to increase after the TOS surface treatment. Biodegradability of the cellulose was evaluated by enzyme treatments and the influence of CaSiO3 and hydrophobic agents was also derived.

Easy reuse of magnetic cross-linked enzyme aggregates of lipase B from Candida antarctica to obtain biodiesel from Chlorella vulgaris lipids.

In this work, magnetic cross-linked enzyme aggregates (mCLEAs) of CALB (lipase B from Candida antarctica) were prepared and characterized. Moreover, a method for an easy, sustainable and economic extraction of lipids from nitrogen-starved cells of Chlorella vulgaris var L3 was developed. Then, the extracted lipids (oils and free fatty acids, FFAs) were converted to biodiesel using mCLEAs and chemical acid catalysis. Among several lipid extraction methods, saponification was selected given the amount of wet microalgal biomass it can process per unit of time, its low market value, and because it allows for the use of less toxic solvents. A biodiesel conversion of 80.2 ± 4.4% was obtained by chemical catalysis (1 h at 100°C) using FFAs and methanol as the alkyl donor. However, a biodiesel conversion of more than 90% (3 h at 30°C) was obtained using mCLEAs and methanol. Both chemical and enzymatic catalysts gave biodiesel with similar fatty acid alkyl ester (FAAE) composition. Methanol, at 15% (v/v) or higher concentration, caused a decrease of lipase activity and a concomitant increase in the size of mCLEA aggregates (up to 2 µm), as measured by dynamic light scattering (DLS). The magnetic character of the novel biocatalyst permits its easy recovery and reuse, for at least ten consecutive catalytic cycles (retaining 90% of the initial biodiesel conversion), using mild reaction conditions and environmentally-friendly solvents.

A screen-printed paper microbial fuel cell biosensor for detection of toxic compounds in water.

Access to safe drinking water is a human right, crucial to combat inequalities, reduce poverty and allow sustainable development. In many areas of the world, however, this right is not guaranteed, in part because of the lack of easily deployable diagnostic tools. Low-cost and simple methods to test water supplies onsite can protect vulnerable communities from the impact of contaminants in drinking water. Ideally such devices would also be easy to dispose of so as to leave no trace, or have a detrimental effect on the environment. To this aim, we here report the first paper microbial fuel cell (pMFC) fabricated by screen-printing biodegradable carbon-based electrodes onto a single sheet of paper, and demonstrate its use as a shock sensor for bioactive compounds (e.g. formaldehyde) in water. We also show a simple route to enhance the sensor performance by folding back-to-back two pMFCs electrically connected in parallel. This promising proof of concept work can lead to a revolutionizing way of testing water at point of use, which is not only green, easy-to-operate and rapid, but is also affordable to all.

Magnetic biocatalysts and their uses to obtain biodiesel and biosurfactants.

Nanobiocatalysis, as the synergistic combination of nanotechnology and biocatalysis, is rapidly emerging as a new frontier of biotechnology. The use of immobilized enzymes in industrial applications often presents advantages over their soluble counterparts, mainly in view of stability, reusability and simpler operational processing. Because of their singular properties, such as biocompatibility, large and modifiable surface and easy recovery, iron oxide magnetic nanoparticles (MNPs) are attractive super-paramagnetic materials that serve as a support for enzyme immobilization and facilitate separations by applying an external magnetic field. Cross-linked enzyme aggregates (CLEAs) have several benefits in the context of industrial applications since they can be cheaply and easily prepared from unpurified enzyme extracts and show improved storage and operational stability against denaturation by heat and organic solvents. In this work, by using the aforementioned advantages of MNPs of magnetite and CLEAs, we prepared two robust magnetically-separable types of nanobiocatalysts by binding either soluble enzyme onto the surface of MNPs functionalized with amino groups or by cross-linking aggregates of enzyme among them and to MNPs to obtain magnetic CLEAs. For this purpose the lipase B of Candida antarctica (CALB) was used. The hydrolytic and biosynthetic activities of the resulting magnetic nanobiocatalysts were assessed in aqueous and organic media. Thus, the hydrolysis of triglycerides and the transesterification reactions to synthesize biodiesel and biosurfactants were studied using magnetic CLEAs of CALB. The efficiency and easy performance of this magnetic biocatalysis validates this proof of concept and sets the basis for the application of magnetic CLEAs at industrial scale.

Magnetic Cross-Linked Enzyme Aggregates (mCLEAs) of Candida antarctica lipase: an efficient and stable biocatalyst for biodiesel synthesis.

Enzyme-catalyzed production of biodiesel is the object of extensive research due to the global shortage of fossil fuels and increased environmental concerns. Herein we report the preparation and main characteristics of a novel biocatalyst consisting of Cross-Linked Enzyme Aggregates (CLEAs) of Candida antarctica lipase B (CALB) which are covalently bound to magnetic nanoparticles, and tackle its use for the synthesis of biodiesel from non-edible vegetable and waste frying oils. For this purpose, insolubilized CALB was covalently cross-linked to magnetic nanoparticles of magnetite which the surface was functionalized with -NH2 groups. The resulting biocatalyst combines the relevant catalytic properties of CLEAs (as great stability and feasibility for their reutilization) and the magnetic character, and thus the final product (mCLEAs) are superparamagnetic particles of a robust catalyst which is more stable than the free enzyme, easily recoverable from the reaction medium and reusable for new catalytic cycles. We have studied the main properties of this biocatalyst and we have assessed its utility to catalyze transesterification reactions to obtain biodiesel from non-edible vegetable oils including unrefined soybean, jatropha and cameline, as well as waste frying oil. Using 1% mCLEAs (w/w of oil) conversions near 80% were routinely obtained at 30°C after 24 h of reaction, this value rising to 92% after 72 h. Moreover, the magnetic biocatalyst can be easily recovered from the reaction mixture and reused for at least ten consecutive cycles of 24 h without apparent loss of activity. The obtained results suggest that mCLEAs prepared from CALB can become a powerful biocatalyst for application at industrial scale with better performance than those currently available.