Fungi in Biotechnology and Sustainability

Role of heterogeneity in productivity of fungi to produce enzymes and small molecules

In the past it was assumed that all fungal cells within a bioreactor are identical and thereby each cell would contribute to the productivity of the fungal fermentation. We have more and more evidence that there is a large heterogeneity in fungal liquid cultures and that this impacts productivity. For instance, small colonies perform better in a culture than large colonies. Yet, the large colonies secrete specific enzymes that are not secreted by the small colonies. Moreover, the large colonies are more stress resistant. We also observe heterogeneity within a colony. The outer zone is more active in enzyme secretion and protects the center from stress. Notably, not every hypha in the outer zone secretes enzymes. Hyphae specialize into secreting hyphae or stress resistant hyphae. Clearly, heterogeneity seems to impact productivity in liquid cultures. We are studying the mechanisms that are involved in these mechanisms.

Use of fungi in bioremediation

Many water bodies are contaminated with man-made molecules such as pharmaceuticals and herbicides. These molecules threaten biodiversity, ecosystems and human health. Conventional waste water treatment plants  do not effectively degrade these micropollutants. White rot fungi produce enzymes that degrade lignin, which consists of complex polycyclic aromatic hydrocarbons (PAHs). These oxidizing enzymes have a broad target spectrum, thereby also including many micropollutants. Furthermore, white rot fungi have been shown to sorb and accumulate heavy metals. In this project, we study different fungi in their capability to degrade and/or sorb micropollutants and the molecular mechanisms that are involved in this process.

Triggers of mushroom formation

Environmental clues such as low CO2, light, changes in temperature, disappearance of inhibiting substances, appearance of inducing substances induce mushroom production. This project aims to uncover the molecular mechanisms by which these cues are perceived and integrated. Do perhaps all of them in the end activate the same transcriptional regulators? Could we then shortcut these inducing signals by initiating fructification independent of the environment? At the moment we focus on the nutritional state, light and CO2 levels as environmental cues for fructification in the model species Schizophyllum commune.

Digesting fungal cell walls

Most of the molecular work done in our lab involves genetic transformation. In fungi this often relies on the digestion of cell walls to get protoplasts (naked cells). This process is executed by enzymes able to degrade different components of the cell wall. These enzymes are often produced by organisms that prey on fungi or organisms that use similar components in their structures as those found in the fungal cell wall. Depending on the fungal species a different enzyme mixture is needed for protoplasting. We aim to understand which enzymes are needed and whether we can make effective customized or one-for-all enzyme mixtures.

Fungal materials

Materials produced with mycelium can offer a sustainable solution to today’s conventional building and crafting materials. In fact, waste streams can be upcycled to produce either pure mycelium materials or composite mycelium materials. Pure mycelium materials are grown on a substrate that can be separated from the fungus afterwards. They can be used to craft for instance leather-like or textile materials. For composite materials, a substrate is colonized by mycelium. They can be purposed as insulation, packaging or construction materials. 

We are studying how we can change the properties of mycelium materials by varying the fungal species, the substrate, the environmental growth conditions and the processing of the materials. By doing so, we were the first to describe wood-, polyethylene-, polyvinylchloride- and rubber-like materials. We not only focus on mechanical properties but also study bioactive properties such as the ability to stimulate the immune system.