EP0282511A1 - Fungus cultivation - Google Patents

Abstract

A bed intended for the cultivation of fungi such as common mushrooms, consists almost entirely of a water-insoluble and water-swellable polymer (such as polyacrylamide), of water and of a liquid nutritive agent, such as an extract mushroom compost or cow manure. Conventional basement layers such as fertilizers and sawdust are not used in said bed, although traditional trays can be used. Said bed can be prepared more quickly and at a lower cost compared to the traditional bed and facilitates mechanical harvesting.

Description

FUNGUS CULTIVATION

This invention relates to fungus cultivation, in particular edible mushrooms.

Mushrooms are widely cultivated. A standard cultivation procedure comprises growing the mycelia in compost. As necessary, the growing mycelia are covered by a layer which must include water in a readilyavailable form, e.g. in the form of water-swollen "beads" of a suitable polymer. Compost must be added weekly; the overall procedure requires considerable handling of the mycelia and is time-consuming. Examples of such techniques can be found in GB-A-2 146 319, GB-A-1 376 091 and JP-A-58212722. In all of these cases, the polymer is used in conjunction with substantial quantities of soil or other substrate, and is used solely to provide a steady supply of available water.

Water-swellable polymers, e.g. the "super absorbent" polymers based on acrylic acid, methacrylic acid, acrylamide, methacrylamide, acrylonitrile or methacrylonitrile, are well known. They have been used as a substrate for the growth of silage, and they have been proposed as a means for providing water to plants in very dry climates, e.g. in deserts.

The present invention uses a radically different approach and provides a method of growing fungi using polymer as substantially the only substrate, with suitable nutrients being provided also.

Thus, the method of the invention uses a water-swellable water-insoluble polymer constituting, when swollen with aqueous liquid, at least 90%, and preferably 95, 99 or 99.5% or more, of the substrate for the fungi. The nutrient may be any suitable nutrient for the fungus in quest ion , but preferably includes lignin, cellulose and hemicelluloses, plus a nitrogen source, minerals and any "hormones" which may be applicable. It has been found that a water-extract of cow dung provides a surprisingly effective and cheap nutrient solution.

The nutrient solution may be used to swell the polymer or may be added later, following swelling of the polymer with water. The nutrient may not be presented as a solution or suspension as such, by may be used as a slurry or as a water-leachable solid matter, not exceeding 10% of the total substrate. The amount will depend on its concentration: conventional mushroom compost may be used at 5%, or concentrated nutrient at 1% or less.

A composition according to the invention comprises a nutrient and water-swollen or water-swellable polymer, in admixture or separately packaged as a kit, the proportion of polymer being at least 90% when swollen.

In conventional mushroom growing techniques, the bed (substrate) is about 12-23 cm deep and is prepared laboriously over an approximately 3 week period. 4 to 9 "flushes" of mushrooms are obtained from a given mass of mycelium, in order to spread the cost of establishing the bed. The bed in accordance with the invention, on the other hand, can be prepared in only 6 to 24 hours, and therefore at a greatly reduced cost. Furthermore, the minimum depth of substrate which is now required may be about 25 mm, which represents a six-fold decrease with respect to the conventional procedure described above. About 2 to 4 cm is, however, preferred. A "single-flush" system is therefore economical and would allow the mushrooms to be picked mechanically, which has not previously been possible. The production time can be 40% less than before.

The bed of substrate and mycelium will usually be "cased" in the conventional way, for example with soil which may or may not contain swollen polymer as is taught in GB-A-2 146 319.

The polymer used in the bed may be any suitable material which is non-toxic for the fungus (and preferably also for humans, in case any becomes mixed in with the harvested mushrooms) and which absorbs sufficient water or aqueous nutrient. Non-ionic polyacrylamides are particularly suitable and may be obtained from S.N.F. Floerger of St. Stienne, France, under the trade designations PROO55P and PROO5A. It has also been found that polyacrylamides are not too prone to contamination with undesirable moulds.

In general, suitable polymers may be derived from monomers such as (meth)acrylic acid and (meth) acrylamide. The monomers or unlinked polymers should be insoluble. Alternatively, the monomers or polymers are soluble, but are cross-linked to be insoluble. Classes of polymer which may be of utility are polyvinyl alcohol, methacrylate-polystyrene, starch-acrylonitrile and polyalkylene oxides. The polymer may be a homopolymer or copolymer, e.g. a graft copolymer. Sodium, potassium or ammonium poly(meth) acrylates may be used; sodium/ potassium may itself be valuable as a nutrient for the fungus. Particular polymers include ammonium polyacrylate cross-linked by 500 ppm. MBA (available from SNF, St. Etienne, France as PB48C); a copolymer of acrylamide and sodium acrylate (70/30) cross-linked by 500 ppm. MBA (PR3005); sodium polyacrylate cross-linked by 50 ppm. MBA (PR9910); sodium polyacrylate cross-linked by 30ppm. MBA and post-treated with 0.2% ethylene glycol diepoxy (PR9910T); a copolymer of acrylamide and potassium acrylate (70/30) cross linked by 20,000 ppm ethylene glycol dimethacrylate (OL610); a copolymer of sodium acrylate and vinyl alcohol (70/30) (avilable from Sumitomo); polyethylene oxide cross-linked by gamma rays; starch grafted with acrylonitrile and saponified; starch grafted with acrylic acid; styrene/maleic anhydride copolymer (salt); PVA/maleic anhydride and a copolymer of acrylamide and dimethyldiallylammonium chloride (95/5) cross-linked by 550 ppm. MBA.

The polymers may be anionics such as polymers of acrylic acid, methacrylic, crotonic, sulphopropylie, vinyl suphonic or styrene sulphonic; nonionics such as polymers of acrylamide, methacrylamide, acrylic esters, vinyl alcohol, vinylacetates, or polyethylene oxide; cationics such as dimethylaminoethyl acrylate or methacrylate salts dimethyldiallylammonium chloride; or copolymers of these water-soluble monomers between themselves or with some insoluble monomers,

These polymers swell in water but do not dissolve because they are cross-linked by (a) monomers with 2, 3 or 4 double bonds, such as ethylene glycol diacrylate or dimethacrylate, methylenebisacrylamide or methacrylate or polyethylene glycol dimethacrylate; (b) by reactive compounds like formaldehyde, glyoxal, amino resins like Kymine (epichlorhydrin, diethylenetriamine, adipic acid) glycol diglycidylether; (c) by gamma or beta rays; or (d) by polyvalent metals like aluminium, iron etc. Such materials may take up water and swell by a factor (w/w) of at least 10, eg. 20 or more, and often 50, 100, 200, 400, 500, 800, 1000, 1200, 1500 or more.

EXAMPLE These trials consisted of forming an expanded polymer bed in a plastic container. The polymers were PR0055P and PR005A, both non-ionic polyacrylamides from SNF Floerger of France. The polymer bed was formed by swelling about 800g of the polymer with approximately 100 litres of water. This process takes 6 - 24 hours. The water used was normal tap water. 5kg of ground-down conventional mushroom compost was used as the nutrient. When the polymer had fully swollen, sterile grain coated with mushroom spores (Agaricus bisporus) was seeded in the polymer beds which varied in depth from 2 cm to 30 cm and the beds were maintained at an air temperature of 23-25ºC and under conventional light conditions. Approximately 14 - 20 days later the polymer bed was cased with a normal mushroom casing layer (peat, clay etc.) and the temperature held at about 23ºC for a further 10 days. The plastic trays were then removed to a cooler place (about 17ºC) with increased air flow for 24 hours, during which time the temperature builds up to about 19ºC and some watering of the casing layer took place. A close study of the results showed that the greater the growth of mycelium the more mushrooms appeared. This would normally be the case.

In an alternative embodiment, the water which is used to swell the polymer is first warmed to about 15ºC or more. This further helps to accelerate the overall growing time.

The main commercial use of the invention is to grow the common field mushroom. (Agaricus campestris,) or button mushroom (A. bisporus), although other edible fungi such as Flammulinaa velupipes Karst, Lyophyllum aggregatum and Pholipa nameko S.Itoh et Imai (which do not need a soil casing) may also be grown in this way.

Claims

1. A kit which comprises a nutrient and waterswellable particles, for preparing a fungal cultivation bed comprising at least 90% swollen polymer.

2. A fungal cultivation bed comprising a nutrient and at least 90% water-swollen particles.

3. A bed according to Claim 2 wherein the swollen polymer comprises at least 95% of the substrate.

4. A bed according to Claim 3 wherein the swollen polymer comprises at least 99% of the substrate.

5. A bed according to any one of Claims 2 to 4 wherein the polymer is a "super-absorbent" polymer based on acrylic acid, methacrylic acid, acrylamide, methacrylamide or methacrylonitrile.

6. A bed according to any one of Claims 2 to 5 wherein the nutrient is a liquid compost, such as a water-extract of cow dung.

7. A bed according to any one of Claims 2 to 6 wherein the nutrient is absorbed into the swollen polymer particles.