GROWING GOURMET - Anto2ni.it

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EVALUATING A MUSHROOM STRAIN
are attracted to a particular Oyster mushroom
strain can be considered a genetically determined
trait—a feature most cultivators would
like to suppress.
26. Nutritional Composition Mushrooms
are a rich source for amino acids (proteins),
minerals and vitamins,The percentages of these
compounds can vary between strains. Substrate
components contain precursors which can be
digested and transformed into tissue to varying
degrees by different strains. This may explain
why there is such a variation in the protein
analysis of, for instance, Oyster mushrooms.
The analyses are probably correct. The strains
vary in their conversion efficiencies of base substrate
components into mushroom flesh.
27. Production of Primary and Secondary
Metabolites A strain's ability to compete may
be directly related to the production of primary
and secondary metabolites. All fungi produce
extracellular enzymes that break down food
sources. Myriads of metabolic by-products are
also generated. These extracellular compounds
are released through the cell walls of the mycehum,
enabling the digestion of potential food
sources. Enzymes, such as higninase which
breaks down the structural component in wood,
are extremely effective in reducing complex
carbon chains, including carbohydrates and hydrocarbons.
Secondary metabolites usually occur well after
colonization. A good example is the yellow
fluid, the exudate, frequently seen collecting atthe
bottom of aged spawn containers. Pleurotus spp.,
Stropharia rugoso-annulata, and Ganoderma
lucidum are abundant producers of secondary metabolites,
especially complex acids and
metabolites forestall
competition from other fungi and bacteria.
28. Production of Medicinal Compounds
Bound within the cell walls of mushrooms are
chains of heavy molecular weight sugars,
polysacharrides. These sugars compose the
structural framework of the cell. Many mushroom
polysacharrides are new to science and
are named for the genus in which they have
been first found, such as lentinan (from
Shiitake, Lentinula edodes), flammulin or
"FVP" (from Enokitake, Flammulina
velutipes), grifolin or grifolan (from Maitake,
Grifolafrondosa), etc. Research inAsia shows
that these cell wall components enhance the
human immune system. Cellular polysaccharides
are more concentrated, obviously, in the
compact form of the mushroom than in the
loose network of the mycelium. In traditional
Chinese pharmacopeia, the sexually producing
organ—in this case the mushroom—has long
been viewed as a more potent source for medicine
than from its infertile representations.
Cell components other than polysaccharides
have been proposed to have medicinal
effects. Strain selection could just as well focus
on their molecular yields. Precursors in the
substrate may play determinant roles in the
selective production of these components
when matched with various strains. (Please
refer to Chapter 21.)
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