Pure mycelium materials: characteristics and applications

Mycelium is the vegetative part of Fungi. It is made up of an interconnected network of hyphae, which are elongated cells with a complex cell wall. Fungi are able to grow on a wide range of substrates thanks to the extended catalytic capabilities of the enzymes they secrete and they have a modular nature, thus they grow by apical extension and lateral branching. They are exploited for a large variety of applications, from bioremediation to drug production. Recently, mycelial biocomposites obtained from the growth of a strain on waste agricultural substrates have been used as materials, which have great thermal and hydrodynamic properties, a low cost of processing and they are easily biodegraded. Previous works from Smart Materials group showed that even pure mycelia have promising features to be employed as materials and in nanotechnological applications. These conclusions are further investigated in the Thesis. The Introduction is an overview of the issues related to plastic use and production and contains a review of the main solutions and alternatives considered up to now. In the second part of the Introduction, mycelia and their applications are described. In Chapter 1, the possibility of finely tune morphological, chemical, hydrodynamic and mechanical properties of pure mycelial materials is investigated by analyzing growth of Ganoderma lucidum in liquid substrates enriched in different components. In Chapter 2, both the porous structure and the chemical and hydrodynamic features of mycelia from Ganoderma lucidum and Pleurotus ostreatus are exploited in the development of suitable bioscaffolds for attachment and growth of Human Adult Fibroblasts (HDFAs)

Biodegradation of Synthetic Polymers in the Aquatic Environment

Biodegradation of synthetic polymers can be a sophisticated property for intelligent and sustainable products that offer complex benefits for specific applications. There are many entry paths for synthetic polymers that can accumulate in the aqueous and especially marine environment and little is known about their biodegradation especially in the aquatic environment. The difficulties with determining biodegradation in those environments are based on the absence of appropriate methods and also the fact that these environments often prove low biodegradation rates. It is also complicated to detect biodegradation on polymeric substances because of the high molecular weight, water insolubility and difficult molecular structure making it hard to detect biodegradation products. This work provides an overview of the actual status of research and investigates on different methods of biodegradation tests in the aquatic environment with selected synthetic polymers

Biodegradation of Synthetic Polymers in the Aquatic Environment

Biodegradation of synthetic polymers can be a sophisticated property for intelligent and sustainable products that offer complex benefits for specific applications. There are many entry paths for synthetic polymers that can accumulate in the aqueous and especially marine environment and little is known about their biodegradation especially in the aquatic environment. The difficulties with determining biodegradation in those environments are based on the absence of appropriate methods and also the fact that these environments often prove low biodegradation rates. It is also complicated to detect biodegradation on polymeric substances because of the high molecular weight, water insolubility and difficult molecular structure making it hard to detect biodegradation products. This work provides an overview of the actual status of research and investigates on different methods of biodegradation tests in the aquatic environment with selected synthetic polymers

Long-term properties and end-of-life of polymers from renewable resources

The long-term properties and end-of-life of polymers are not antagonist issues. They actually are inherently linked by the duality between durability and degradation. The control of the service-todisposal pathway at useful performance, along with low-impact disposal represents an added-value. Therefore, the routes of design, production, and discarding of bio-based polymers must be carefully strategized. In this sense, the combination of proper valorisation techniques, i.e. material, energetic and/ or biological at the most appropriate stage should be targeted. Thus, the consideration of the end-of-life of a material for a specific application, instead of the end-of-life of a material should be the fundamental focus. This review covers the key aspects of lab-scale techniques to infer the potential of performance and valorisation of polymers from renewable resources as a key gear for sustainability

Lifetime prediction of biodegradable polymers

The determination of the safe working life of polymer materials is important for their successful use in engineering, medicine and consumer-goods applications. An understanding of the physical and chemical changes to the structure of widely-used polymers such as the polyolefins, when exposed to aggressive environments, has provided a framework for controlling their ultimate service lifetime by either stabilising the polymer or chemically accelerating the degradation reactions. The recent focus on biodegradable polymers as replacements for more bio-inert materials such as the polyolefins in areas as diverse as packaging and as scaffolds for tissue engineering has highlighted the need for a review of the approaches to being able to predict the lifetime of these materials. In many studies the focus has not been on the embrittlement and fracture of the material (as it would be for a polyolefin) but rather the products of degradation, their toxicity and ultimate fate when in the environment, which may be the human body. These differences are primarily due to time-scale. Different approaches to the problem have arisen in biomedicine, such as the kinetic control of drug delivery by the bio-erosion of polymers, but the similarities in mechanism provide real prospects for the prediction of the safe service lifetime of a biodegradable polymer as a structural material. Common mechanistic themes that emerge include the diffusion-controlled process of water sorption and conditions for surface versus bulk degradation, the role of hydrolysis versus oxidative degradation in controlling the rate of polymer chain scission and strength loss and the specificity of enzyme-mediated reactions

Processing of Hemp Fibre Using Enzyme/Fungal Treatment for Composites

Hemp fibres compete very well with glass fibres in terms of their specific strength and stiffness and so can replace glass fibres as reinforcement in composites. Combining them with thermoplastics results in potentially cheap recyclable composite materials. The adhesion between the hemp fibre and thermoplastics such as polypropylene is a major factor in the mechanical properties of the composite. Interfacial bonding can be improved by modifications to the fibres, the matrix or both the fibres and the matrix. The aim of this thesis was to investigate low cost and efficient fibre treatment methods with low environmental impact such as bag retting and white rot fungi, and chelator/enzyme treatments which could be applied to hemp fibre in order to create better bonding fibre for potentially recyclable composite materials. Bag retting was carried out by keeping fresh green hemp fibres in a sealed plastic bag for 1 to 2 weeks to allow natural retting to occur under sealed conditions. For white rot fungi treatments, the dried non-retted hemp fibres were gamma irradiated, and then inoculated with white rot fungi for 2 weeks. Chelator/enzyme treatment was achieved by immersing the fresh green non-retted hemp fibres in solutions consisting of either EDTMP.Na5 (ethylene diamine tetra (methylene phosphonic acid pentasodium salt) or pectinase (P2401) and laccase (53739) for 6 hours. Several characterization techniques, namely wet chemical analysis, Fourier-transform infrared (FT-IR), scanning electron microscopy (SEM), fibre density testing, X-ray diffraction (XRD), differential thermal analysis (DTA) and thermogravimetric analysis (TGA), zeta potential and single fibre tensile testing were used to assess the effect of treatment on hemp fibres. Wet chemical analysis and FT-IR, were used to measure the chemical compounds present in untreated and treated hemp fibres and showed all treatments removed non-cellulosic compounds from hemp fibre. The separation of untreated and treated fibres was investigated by visual inspection. An examination of surface morphology of hemp fibres carried out using SEM revealed that all treated fibres had cleaner hemp surfaces than untreated ones. The fibre density testing showed that the treated fibre had higher density than untreated fibre. XRD was carried out to assess modification of the crystallinity of fibres and the results showed hemp fibre crystallinity index increased in all treated fibres. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) were used to obtain the activation energies and relative thermal stability of fibres, and indicated that all treatments improved fibre thermal stability. Zeta potential indicated that all treated fibres were more hydrophilic than untreated fibre. Single fibre tensile testing was used to obtain the tensile strength of untreated and treated fibres and it was found that the tensile strength of all treated fibres was reduced. Short fibre composites were produced by extrusion and injection moulding. Fibres, polypropylene (PP) and a maleated polypropylene (MAPP) coupling agent were compounded using a twin-screw extruder, and then injection moulded into composite tensile test specimens. It was found that all fibre treatments increased the tensile strength of composites. White rot fungi Schizophyllum commune (S.com) treated fibre gave the highest tensile strength of 45 MPa, an increase of 28% compared to composites using untreated fibre. Both the single fibre pull-out test and the Bowyer and Bader model were used to determine the interfacial shear strength (IFSS) of untreated fibre and S.com treated fibre composites. The results obtained from both methods showed that IFSS of the treated fibre composites was higher than that for untreated fibre composites. This supports that the hemp fibre interfacial bonding with PP was improved by white rot fungi treatment. The Bowyer and Bader model was also used to calculate the tensile strength of untreated and S.com treated short fibre composites and results closely match the experimentally values

Biocomposites

Biocomposites are composite materials consisting of either a polymer matrix or a filler based on biological resources. They have been widely used in numerous applications such as storage devices, photocatalysts, packaging, furniture, biosensors, energy, construction, the automotive industry, and so on due to their great versatility and satisfactory performance. This book focuses on composites made from natural materials (natural fibers and biopolymers) and relates their physical, mechanical, electrical, structural, and biological characteristics as well as their potential applications in biomedicine, pharmaceuticals, and engineering

Myth or reality? – Assessing the suitability of biodegradable plastics within a circular bioeconomy framework

The proposition of a circular bioeconomy framework was introduced as a means of moving from a fossil-based to bio-based economy. With an emphasis on resource efficiency and waste valorisation, it has supported the development of biodegradable bioplastics (BBPs), notably in food packaging applications. Designed to be treated alongside organic waste, BBPs open new streams for plastic waste management within the food-energy-waste nexus, but their suitability in the current social, policy and sustainability landscape remains to be determined. Taking a systems-thinking approach, this thesis explores the compatibility of (certified) BBP packaging under a circular bioeconomy framework, focusing on a co-mingled food and BBP waste stream for anaerobic co-digestion. It uncovers major technical, policy and social challenges and urges for caution when deploying these novel plastic packaging materials on the consumer market. Chapter 1 provides a brief introduction to BBPs and their framing in the wider context of plastic sustainability and organic waste management, followed by aims and objectives in Chapter 2. Chapter 3 provides a comprehensive literature review, depicting the importance and ubiquity of plastics, their environmental impact and the role BBPs could play in a circular bioeconomy framework from a systems-thinking perspective. Chapter 4 details the anaerobic co-digestion treatment of different BBPs with food waste and the impact of BBPs on biogas and methane yields and on microbial communities. The need for consistent experimental design of co-digestion trials is also discussed. Guided by these results, Chapter 5 presents the outcomes of a stakeholder study on attitudes towards BBPs in the current waste management infrastructure and policy landscape to explore how BBPs are perceived and managed on-the-ground in the United Kingdom. Chapters 6 & 7 build on a major finding from the stakeholder study, which outlined the importance of consumers in enabling circularity in the system. Chapter 6 covers a systems framework developed to identify and structure systemic factors that influence how consumers interact with BBP packaging, with a focus on disposal routes. The framework is then applied in practice, based on a survey conducted at two academic institutions, and the role of contextual setting is explored through a comparative case study presented in Chapter 7. Chapter 8 extends the debate on the suitability of BBPs further upstream in the value chain and consumption system and addresses the functional properties of BBP packaging in the context of a shelf-life study, anchoring BBPs in the food system they are embedded within. Chapter 9 summarises key findings and suggests future research related to this thesis. The Appendix contains supplementary figures and data for Chapters 4-8.Open Acces

Early and differential bacterial colonization on microplastics deployed into the effluents of wastewater treatment plants

Título del Post Print: Early and differential bacterial colonization on microplasticsMicrobial colonization of microplastics (MPs) in aquatic ecosystems is a well-known phenomenon; however, there is insufficient knowledge of the early colonization phase. Wastewater treatment plant (WWTP) effluents have been proposed as important pathways for MPs entry and transport in aquatic environments and are hotspots of bacterial pathogens and antibiotic resistance genes (ARGs). This study aimed at characterizing bacterial communities in the early stage of biofilm formation on seven different types of MPs deployed in two different WWTPs effluents as well as measuring the relative abundance of two ARGs (sulI and tetM) on the tested MPs. Illumina Miseq sequencing of the 16S rRNA showed significant higher diversity of bacteria on MPs in comparison with free-living bacteria in the WWTP effluents. β-diversity analysis showed that the in situ environment (sampling site) and hydrophobicity, to a lesser extent, had a role in the early bacterial colonization phase. An early colonization phase MPs-core microbiome could be identified. Furthermore, specific core microbiomes for each type of polymer suggested that each type might select early attachment of bacteria. Although the tested WWTP effluent waters contained antibiotic resistant bacteria (ARBs) harboring the sulI and tetM ARGs, MPs concentrated ARBs harboring the sulI gene but not tetM. These results highlight the relevance of the early attachment phase in the development of bacterial biofilms on different types of MP polymers and the role that different types of polymers might have facilitating the attachment of specific bacteria, some of which might carry ARGsFinancial support was provided by the Spanish Ministry of Economy and Competitiveness (CTM2016-74927-C2-1/2-R