Fungiculture
Introduction
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Fungiculture is the cultivation and production of edible and medicinal mushrooms. Mushrooms are the fruiting bodies, or sporophores, of filamentous chemoorganotrophs of the kingdom Mycota. Fungiculture has a rich history of practice, and considerable significance in the global economy.
Along with fermentation and composting, fungiculture should be considered one of the first microbial biotechnologies. Although mushrooms themselves are macroscopic, their production is based on the manipulation of microbial habitat, community composition, or both, in the presence of the spores or mycelium of a desired fungal species, in order to create conditions favoring mycelial growth and mushroom formation.
For the purposes of production, mushrooms can be roughly divided into two groups: primary and secondary decomposers. Though the boundary between the two groups is not absolute, the two groups of mushrooms require distinct cultivation techniques, and will be discussed separately. Some mushroom species are able to occupy different niches depending on environmental conditions.
Primary Decomposers
Niche
Primary decomposing fungi include both wood-decay fungi, such as shitake (Lentinula edodes), oyster mushroom (Pleurotus spp.), and maitake (Grifola frondosa), and litter-decomposing fungi, including winecap (Stropharia rugosoannulata).
The wood-decay fungi are divided, in turn, into two groups: brown-rot, which degrade cellulose and hemicellulose, and white-rot, which degrade lignin as well as cellulose and hemicellulose. The white-rot fungi, in particular, play a crucial role in the global carbon cycle, by virtue of their ability to decompose large, complex lignin molecules, which constitute the most recalcitrant form of carbon found in plant material. Biodegradation of lignin is not thoroughly understood, but some of the more well-researched pathways involve the lignolytic enzymes manganese peroxidase, lignin peroxidase, and cellobiose dehydrogenase.
It is the activity of these fungi that releases the nutrients and energy stored in the structural elements of plants, which get their strength and rigidity from an abundance of lignin, into a form usable by other organisms. Most of the wood-decaying fungi under cultivation are white-rot fungi, including the above-mentioned L. edodes, Pleurotus spp, and G. frondosa. Mushroom growers exploit the ability of fungi to digest substances that many organisms cannot, by pairing mushroom crops with semi-selective substrates that are nutritionally inaccessible to potential competitors.
Physical environment
Substrates for the production of these mushrooms generally consist of dried, shredded, plant material, with very low nitrogen content. The C:N ratio in the wastes preferred by L. edodes and P. ostreatus range from 350:1 to 500:1. The most common material used for the production of wood-decaying fungi is sawdust, but techniques for growing nominally wood-decaying fungi on grasses are well-established for some mushroom crops. The shredding or pulverizing of the substrate material facilitates the ramification of the fungal mycelium throughout the substrate. This is significant for mushroom producers for several reasons. Together with other factors, the speed of colonization controls the time necessary to produce a crop, and the amount of substrate accessed by the mycelium controls the yield per unit. A fine, granular substrate structure, which permits faster and easier ramification, consolidation, and breakdown, by fungal mycelia, will produce higher yields, sooner, than bulkier substrates.
Microbial Processes: Competition-Contamination
The preference of primary decomposer wood-decay fungi for the relatively microbially simple environment found within undecayed wood, means that these fungi can be very vulnerable to microbial competition, when present. This makes manipulation of the microbial environment fairly straight-forward for mushroom growers - in theory. Most commercial cultivation involves sterilization of the substrate, prior to inoculation with the desired species.
In practice, fungi growing in sterilized substrates are vulnerable to contamination by other fungal or bacterial organisms. The oligomers that are the result of fungal enzymatic breakdown of lignin and cellulose are a viable source of nutrition for a wide range of bacteria as well - and fungi grown in sterile environments are less resilient to the presence of bacteria than they are in their natural habitat. In the wild, fungal-bacterial interactions range from competitive to mutualistic (de Boer). The presence of any other fungal or bacterial organism in a given container of mushroom substrate is generally regarded as a total loss of that container’s production.
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Microbial communities
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Microbial processes
What microbial processes define this environment? Describe microbial processes that are important in this habitat, adding sections/subsections as needed. Look at other topics in MicrobeWiki. Are some of these processes already described? Create links where relevant.
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Current Research
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References
Edited by <your name>, a student of Angela Kent at the University of Illinois at Urbana-Champaign.
