Shaojun Xiong

To support a growing global population (8.5 billion by 2030 and 10 billion by 2050) without further deteriorating Earth’s climate and biodiversity, it is pivotal to develop new technologies not only for the sustainable production of healthy food, but also for increasing energy and resource efficiency and reducing greenhouse gas emissions. One important strategy is the use of local residual bioresources, including crop and forest residues, for food, fuel, and biomaterials within a circular economy approach. Today, the food industry is energy-intensive, with fossil fuels still dominating the energy supply. Existing technologies for producing second-generation biofuels from biomass, such as bioethanol, as well as biomaterials, are costly and often associated with environmental challenges, typically due to the use of chemicals in the processes.

Over the past 15 years, my research has focused on the development of biological (fungal) pretreatment methods of lignocellulosic materials to enable the utilization of residual biomass for food and bio-based products. We believe that the approach of “combined production of edible mushrooms and biofuels/bio-based products” will be important not only in Sweden but also globally. The scientific basis of this approach is that edible mushrooms, such as shiitake (Lentinula edodes) and oyster mushrooms (Pleurotus spp.), are white-rot fungi and protein-rich food sources, but also can selectively degrade lignin and hemicellulose in the lignocellulosic substrates on which they grow. Consequently, after mushroom harvest, the spent mushroom substrate (SMS) becomes cellulose-rich and ready for bioconversion (e.g., through enzymatic or fermentation processes) into cellulosic ethanol or other cellulose-based bioproducts, without the need for chemical pretreatment.

One example of our R&D activities is the development of “Sustainable mushroom production for dual products – food and biofuel” (IVAs-100 lista 2021 and IVAs-100 lista 2022). This work includes three major innovations:  

1)     An efficient fungal pretreatment of lignocellulose substrate by white-rot edible-fungi to maximize lignin degradation while minimizing cellulose loss. This enables the direct use of SMS for cellulose ethanol production without any chemical treatment. 

2)     Novel processes for automatic mushroom cultivation. A patented growing device and process allow for the potential robotisation of the production chain, thereby significantly reducing the labour costs and cultivation time. 

3)     Climate-smart method for pasteurizing mushroom substrates (patented). In this method, hot air (75 – 90 °C) is used instead of conventional pressurised steam (121°C, 2 bar), reducing energy consumption by 60% and CO2 emission by 65%.  

Together, these innovations facilitate industrial upscaling.

More recently, we have also explored the use of SMS for the production of functional biomaterials, in collaboration with researchers in Luleå Technology University. It has been successfully demonstrated that the SMS can be directly processed, without conventional chemical treatment, to isolate cellulose and remove lignin in biomass for nanofiber production. The nanofibers can then be used to produce packaging materials, film and foam. Compared to conventional chemical processes, this approach can significantly reduce environmental impacts associated with toxic substances into the environment.

On-going projects

Finding Peat Alternatives for Agriculture in Swedens Most Abundant Industrial Waste Streams (Alternative Peat)

Financing: MISTRA 2025-2028, with total budget 6 million SEK. Participants: Ulrike Schimpf (Coordinator) and Mika Sipponen, Stockholm University; Lauren McKee, KTH; and Shaojun Xiong, SLU. Company partner: Svamplådan (https://svampladan.se/).

The goal of this project is to diminish the use of peat for casings in mushroom production and find alternatives for critical peat-dependent species like the common button mushroom, Agaricus bisporus. The extraction of peat from natural landscapes releases long-stored carbon, leading to major greenhouse gas emissions. The research aims to develop sludge blends that mimic peat’s properties, investigate microbial interactions in the sludge, and assess its effect on mushroom growth, safety, and quality.

Mushroom-based processes for increased local production of non-meat protein and enhanced agriculture sustainability (MUSA) 

Financing: Nordfork 130266/ FORMAS, 2023-2026, with total budget 7 million NOK. Participates: Carlos Martín (Coordinator, Inland Norway University of Applied Sciences), Shaojun Xiong (Swedish Manager, SLU), Volkmar Passoth (SLU), Malin Hultberg (SLU), Oksana Golovko (SLU), Kadri Pöldmaa (University of Tartu).

MUSA intends to contribute to enhancing agriculture sustainability by (i) using forest and crop residues from Nordic countries for producing edible mushrooms, and (ii) upgrading mushroom spent substrate (SMS) for uses supporting food production, substitution of mineral fertilizers and providing wastewater bioremediation solutions. The project will focus on shiitake (Lentinula edodes) and oyster (Pleurotus spp.) mushrooms, which are climate-smart protein-rich food sources beneficial for human nutrition and wellbeing. The project will develop methods for extracting bioactive compounds from SMS, such as polyphenolics and proteins, and the extraction residue will be saccharified for producing hydrolysates that will serve as substrates for cultivating oleaginous yeasts. The produced yeast will be directed to extraction of lipids that can substitute imported plant oil. SMS feasibilities as fertilizer or soil amendment will be investigated, which include assessments of using SMS as peat substitute in horticulture, effect of microbial community in SMS on soil amendment, and using SMS for removal of micropollutant from wastewater to be used for irrigation.  

Fungal protein and lipids from lignocellulose 

Financing: FORMAS 2022- 2025, with Total budget: 6 million SEK. Participants: Volkmar Passoth (coordinator, SLU), Shaojun Xiong (SLU) and Carlos Martín (Inland Norway University of Applied Sciences).

This project aims to convert non- edible residues from forestry and agriculture (lignocellulose, i.e. residues of wood and straw) to food and high- value food ingredients. This will be achieved by first growing edible fungi (Pleurotus spp and Lentinula spp) on selected substrates, with an optimisation towards producing the optimal amounts of mushroom protein (fruiting bodies) and facilitating down-stream extraction and production of bioactives and microbial oil from the spent mushroom substrate (SMS).