Fungal Highways and Calcite Columns: Co-Cultivating a Mycelium-Bacteria-Based Composite

The research project engages with the motivation of the thesis, of investigating organic and specifically microbially bound composites in the search for alternative construction materials, building on replenishable resources and low-embodied emissions, to enable a sustainable shift towards a bio-based construction paradigm. With today´s most common choices of load-bearing materials; cement, steel and concrete; the construction industry is contributing to about 37 % of the global green-house-gas emissions released into the atmosphere. The aim of this research is to improving the mechanical properties of bio-based solutions, to expand the material choices beyond timber-based materials for load-bearing capacities. While mycelium-bound composites (MBC) are presenting an effective method of naturally binding organic by-products and waste-streams, one of the core challenges faced is the improvement of their mechanical properties.
This thesis investigates whether the increasing of a microbial culture to a coculture including more than one species can present a method of optimization of the therethrough formed material. It is building on precedents, leveraging binding qualities presented by living microorganisms. The two mechanisms investigated in this research are, first, the fungal binding of organic substrate through the expansion of their vegetative network, the mycelium, and second the biomineralisation induced by a ureolytic bacterium. This thesis is synthesising between these two mechanisms, using the fungal species Ganoderma lucidum and the bacterial species Sporosarcina pasteurii to investigate the thereby presented double binding mechanism. Insights were made on the fungal development of a spatial network, the bacterial dispersal on the formed mycelium and the biomineralisation of the fungus as scaffold and the increase of the mechanical properties compared to the monoculture.
The interdisciplinarity of the research has been a key driver by using a Research through Design approach and borrowing of tools and technology of microbiology to evaluate the material formation. The research has been undertaken through a Probe-Prototype-Demonstrator approach to develop methods, protocols and processes. The dissertation is divided into three parts which are correlating with the research modes of the Design Probe, the Material Prototype and the Demonstrator. The first part, the Design Probe, elaborated on the beginnings of the experimental work, through explorative studies, first investigating the lowest amount count of parameters and with every new insight, increasing those. This experimental phase, by identifying the feasibilities and the essential parameters, it has laid the foundation to then enter into the Material Prototype. This research phase has been dedicated to understanding the material behaviour and formation through microbial interaction. This part has been executed with the researchers from Ghent University and presented a tool to understand the core reactions of the microorganisms on each other and in terms of biomass production to serve as binder. The third Demonstrator, has been a useful tool to investigate the composite material against real-world challenges, forces and combinations with other technologies or materials.
The findings of this thesis contribute to three key fields, the material, the microbiological and the methodological advancements. 1) The material advancement has been made in the development of a novel process using the cocultivation of a filamentous fungus, G. lucidum, with the ureolytic bacterium, S. pasteurii. This interaction allows for the fungal network, on the one hand binding the composite, while on the other presenting a strategy of mobility through the substrate to the bacterium. The cocultivation has been found to benefit both species´ cell growth and by motility of the biomineralising bacterium through the composite, thereby, in certain conditions, uniformly spread precipitated minerals. This is referred to as a double-binding mechanism and has brought forward a significant increase in the mechanical properties of the material when compared to a monocultured MBC. 2) The microbiological advancement in this research is the expansion of methods of cocultivation. While this method is often connected to the extraction or analysis of specific molecules produced by one of the cocultured species, this research is investigating the potential benefits in terms of material formation. This research is therefore investigating the biomass formation, the morphologies of the attached biominerals and the conditions of successful growth. 3) The methodological advancements have been brought forward by utilising and expanding the methodology of Research through Design by applying the framework of the Probe-Prototype-Demonstrator to a microbiological development aim. It has served as a way of evaluation of the novel formed materials and to organise the way of thinking, synthesising of methods and later reconnecting the insights with an architectural context.