By Gary Mills

Gourmet Mushrooms, Inc., Michigan operation, was formed in 2013 when the parent company purchased the existing mushroom plant located in Scottville, MI from Diversified Natural Products, Inc.  The Scottville facility is located 10 miles from Lake Michigan in the heart of Michigan’s hardwood lumber industry.  Fresh water and the byproducts from the lumber industry are key ingredients for a successful specialty mushroom operation.  The Scottville plant has the capability of pumping tens of thousands of gallons of water per day and access to thousands of cubic yards of waste lumber products (sawdust, woodchips, bark & leaf compost) that require minimal transport.  The plant consists of approximately 200, 000 square feet under-roof located on about 79 acres of land with rail access separating the north and south building complexes.  The buildings house 27 growing rooms, coolers, packaging area, offices, processing area, fermentation capabilities, laboratory facilities and a soil shed.  It is equipped with major heating and cooling infrastructure.

The North building is used for processing, bag and jar inoculation and incubation.  Each week bags and jars are prepared, sterilized and inoculated after cooling to ambient temperature.  There is room at the plant to triple the capacity of bottles as demand increases.  The North building also houses the clean room, laboratory and culture repository for the proprietary strains.   A total of seven culture rooms and a jar preincubation room are in the North Building as well as production and shipping for mushrooms kits that GMI, Inc. contract manufactures for Back-To-The-Roots.

The South building consists of 20 additional growing rooms. Each growing room has an individual air handling unit as well as separate controlled humidification.  In addition to the 20 incubation/growing rooms the South building has 2 large coolers, a packaging area, employee break room and office area for shipping/packaging personnel.  All bottle incubation and cultivation for the wood degrading mushrooms is conducted in the South building.   The South Building also houses the maitake incubation and growing rooms which utilize bag cultivation technology.  Figure 1 shows the outside of the North Building, the inside of the South Building, growing rooms and maitake bag cultivation in a growing room.

The bag cultivation of maitake is like the jar cultivation technology that GMI uses for its other mushrooms both processes can be divided into the vegetative growth of the fungus and the reproductive or fruiting stage in which the mushroom forms.  The entire process can be presented in the following schematic diagram:

The process begins with blending of the nutrient substrate ingredients, which are mixed with the appropriate amount of water to hydrate the mix to specific moisture content.  The mixed substrate ingredients are added to a container, either an autoclavable polypropylene bag in the case of maitake or jar.  The containers once filled are sterilized in a retort, a pressurized heating vessel used in the canning industry.  After sterilization, the containers are placed in a cooling room where they remain until they reach ambient temperature.  The containers once cooled are transferred to a sterile clean room where they are aseptically inoculated with mushroom spawn.  After inoculation, the containers are sealed and are taken to the appropriate species spawn room where they can incubate at a controlled temperature and humidity, for maitake this is about 5 weeks.  After incubation, the fungal cultures are induced to shift from the vegetative to the sexual stage and are placed in the species-specific growing room where they can fruit, a process that takes about 3 additional weeks for maitake.  Once the mushrooms reach the appropriate size and have the desired characteristics they are harvested.