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Development of an energy efficient bulk sterilisation technique for the production of mycelium (BULK SUBSTRATES)

Final Report Summary - BULK SUBSTRATES (Development of an energy efficient bulk sterilisation technique for the production of mycelium)

The objective of project BULK SUBSTRATES was the development of a bulk production system for the safe, cost effective and energy friendly production of axenic mycelium. The latter is meant to replace the labour-intensive and risky procedure, based on the hygienisation of individual substrate portions. The new method includes bulk sterilisation of raw materials, followed by aseptic cooling and inoculation, and portioning under strictly hygienic conditions.

Europe experiences a rapidly growing demand for food-related mycelium products, such as mushrooms, fermented food products, mycelium for biocontrol and inoculum for composting. The raw materials used in such Solid state fermentations (SSF) are infection sensitive products, such as grain mixtures and agricultural wastes. Unsafe hygienisation and inoculation lead to variable yield and quality. The regular supply of a standardised mycelium product will lead to a stable market, and thus to a stable income for the producers.

Sterile handling was a top priority, and attention was given to energy saving and labour friendliness. Professional mycelium producers will largely benefit from this production procedure: on the one hand, they will directly improve their rentability, on the other hand the market will be stimulated by the regular supply of a standardised product, with increased sales as a result.

The application of the proposed secure production system is expected to directly improve the competitiveness for the users, thanks to:
- a regular production, without the permanent risk of failures;
- labour and energy efficiency;
- a standardised commodity;
- independence of external circumstances;
- optimal mycelial colonisation resulting in better yields;
- increase in production capacity;
- a competitive price for the achieved product.

The project included five research work packages (WPs), each of them highlighting an aspect that is crucial in the process. In WP 2 a large number of substrate components have been inventoried and checked for relevant properties. A lab scale rolling drum mixer was used to study heat exchange under Task 2.4. and made conclusions regarding the mixer design. The choice of the agitator was determined under Task 2.3. with the help of a pilot scale mixer. WP 3 has delivered appropriate inoculating systems for solid as well as liquid inocula, while in WP 4 was designed a safe system to fill pre-sterilised bags with the cooled and inoculated substrate. WP 5 resulted in a multifunctional prototype, provided with appendages for e.g. air removal, steam injection and cleaning in place (CIP), and sensors for temperature, moisture content, and pressure control. In WP 6, semi industrial production trials gave a view on the uniformity, production rate and quality of the final product.

The exploitable result is a device for the bulk production of mycelium on sterilised substrates. The first users will be most probably the members of the consortium, who can freely use the knowledge to construct a machine adapted to their own requirements.

The machine can be used for different types of industrial SSF, such as the production of:
-mushroom spawn;
- substrates for mushroom production;
- additives for animal feed;
- fungi for crop protection;
- malt incubated with imperfect fungi;
- neutraceuticals based on mycelium on grains.

The project resulted in the construction of a prototype which meets the demands of all partners. It is suitable for SSF with mycelium of higher fungi such as edible mushrooms, lower fungi like Rhizopus sp. and Beauveria sp., and even some categories of bacteria. A large range of substrates and substrate mixtures can be used, ranging from grains and seeds over sawdust and shredded straw.

The prototype consists of:
- a dust-free bag emptying device;
- a horizontal mixer with a volume of 1 200 litres and a filling capacity of 600 litres. It is provided with a jacket for heating and cooling;
- a dosing unit on the bottom of the mixer, equipped with the necessary valves;
- an automatic filling device which is completely encased in a sterile environment;
- laminar air flow cabinets for inoculation with liquid or solid inoculum;
- necessary appendages for clean steam, compressed air and 'Cleaning in place' (CIP).

The intellectual property and the prototype being own by the group of SME's, all members have free access to the latter for their own use. An agreement on the utilisation of the prototype and the commercialisation of the design has been signed by all members of the consortium.

As far as commercialisation is concerned, there are different options.
- The machine and its appendages can be sold to interested parties as a combination, either by the consortium or members thereof, or by their representatives.
- The bag filling device, which is designed as a part of it, can be separately commercialised. As it will allow the filling of dry and humid granular mixtures under sterile conditions, the food industry and pharmaceutical industry may be also interested in this machine.