Soňa Hermanová

Anaerobic digestion of aliphatic polyesters

Anaerobic processes for the treatment of plastic materials waste represent versatile and effective approach in environmental protection and solid waste management. In this work, anaerobic biodegradability of model aliphatic polyesters, poly(L-lactic acid) (PLA), and poly(ɛ-caprolactone) (PCL), in the form of powder and melt-pressed films with varying molar mass, was studied. Biogas production was explored in batch laboratory trials at 55 ± 1°C under a nitrogen atmosphere. The inoculum used was thermophilic digested sludge (total solids concentration of 2.9%) from operating digesters at the Central Waste Water Treatment Plant in Prague, Czech Republic. Methanogenic biodegradation of PCLs typically yielded from 54 to 60% of the theoretical biogas yield. The biodegradability of PLAs achieved from 56 to 84% of the theoretical value. High biogas yield (up to 677 mL/g TS) with high methane content (more than 60%), comparable with conventionally processed materials, confirmed the potential of polyester samples for anaerobic treatment in the case of their exploitation in agriculture or as a packaging material in the food industry.

Nanoparticles Based on Poly(trimethylene carbonate) Triblock Copolymers with Post-Crystallization Ability and Their Degradation in vitro

Aliphatic polycarbonate-based block copolymers have received considerable attention as carriers for targeted drug and gene delivery because of their biocompatibility and biodegradability. However, there is little understanding of their phase behaviour and physicochemical characterization of the particles made from them. Here, we prepared a series of well-defined poly(trimethylene carbonate) (PTMC)-based copolymers with molar masses of 3–9 kg·mol-1 by metal-free ring-opening polymerization using dihydroxy-terminated poly(ethylene oxide) as a macroinitiator. Micellar nanoparticles self-assembled from copolymers had a size of less than 130 nm. They were degraded by the action of a model lipase from Mucor Miehei at 37 °C, which is of high importance for biodegradability in the living organism. X-ray diffraction and differential scanning calorimetry proved that amorphous copolymers with more than 39 mol% of carbonate units and representative particles were prone to the rearrangement of PTMC chains during storage and to thus undergo post-crystallization. Our findings can contribute to the comprehensive characterization of polycarbonate biomaterials for medical applications.

Fluorographene and Graphane as an Excellent Platform for Enzyme Biocatalysis

The application of enzymes is a crucial issue for current biotechnological application in pharmaceutical, as well as food and cosmetic industry. Effective platforms for enzyme immobilization are necessary for their industrial use in various biosynthesis procedures. Such platforms must provide high yield of immobilization and retain high activity at various conditions for their large-scale applications. Graphene derivatives such as hydrogenated graphene (graphane) and fluorographene can be applied for enzyme immobilization with close to 100 % yield that can result to activities of the composites significantly exceeding activity of free enzymes. The hydrophobic properties of graphene stoichiometric derivatives allowed for excellent non-covalent bonding of enzymes and their use in various organic solvents. The immobilized enzymes retain their high activities even at elevated temperatures. These findings show excellent application potential of enzyme biocatalysts immobilized on graphene stoichiometric derivatives.

The Impact of Graphite Source and the Synthesis Method on the Properties of Graphene Oxide

The purpose of this study is to insight more thoroughly into the structural properties of graphene oxide (GO) in particular of the type generated by Hummers method in relation with graphite precursor originating from different sources. The systematic study using elemental analysis (EA), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) was performed to reveal the changes of GO microstructure. The results revealed considerable influence of both the original graphite source and isolation procedure of GO by lyophilisation. Further, maintaining of GO in a form of aqueous colloidal dispersion is crucial for preservation of its unique properties. SEM results revealed the occurrence of associated GO blocks formed form identically oriented planes.