Purification and identification of the growth promoting substance from corn fiber and its promotion mechanisms on useful mushroom productions

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Corn fiber (CNF) is an abundant by-product of the wet corn milling process in the production of corn starch. We have shown that the hot water soluble fraction (HWSF) from CNF has a promoting effect on the mycelial growth of various edible mushrooms including mycorrhizal mushroom such as Tricholoma matsutake and so on. Moreover, fruit-body yield increased at 1.2-1.6 times by using CNF, and the cultivation period was dramatically shortened compared to that of the control without CNF. To reveal the promoting mechanisms, the effect of CNF-HWSF on the stimulation of extracellular enzymes was examined. As a result, the production of carbohydrases such as amylase, CMCase and xylanase were markedly enhanced by the addition of low molecular weight fractions (less than M.W.500) prepared from CNF-HWSF. The enzymatic stimulations and enhancement of mycelial growth appeared during the about same time on the culture period. Furthermore, fraction less than the M.W.500 was separated by gel filtration into 5 fractions, and the effect of each fraction was investigated. The promoting effects were indicated even on a fraction D has no sugars and amino acids in CNF-HWSF, From these results, the promoting effect by CNF-HWSF seems to be a 2 step reactions. The first step could be achieve by rich nutrients such as mono- and ologo-saccharides and free amino acids from CNF-HWSF. The second step considered that the marked promoting effect was caused by the stimulation of extracellular enzymes. Now, we are in the improvement stage for practical application of CNF as a growth substrate using sawdust-based cultivation. Further attempts will be made to investigate the isolation and the characterization of promoting substances in CNF-HWSF to clarify the promotion mechanisms on edible mushrooms.