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

玉米纤维(CNF)是玉米淀粉湿法加工过程中产生的大量副产物。结果表明，CNF热水可溶部分(HWSF)对包括松茸等菌根蘑菇在内的各种食用菌的菌丝生长均有促进作用。与不施CNF的对照相比，施CNF的子实体产量提高了1.2~1.6倍，培养周期明显缩短。研究了CNF-HWSF对胞外酶的刺激作用，以揭示其促进作用的机制。结果表明，由CNF-HWSF制备的低分子量组分(分子量小于500)显著提高了淀粉酶、CMCase和木聚糖酶等碳水化合物酶的产量。在培养过程中，酶促生长和菌丝生长的促进作用几乎同时出现。此外，通过凝胶过滤将相对分子质量小于500的组分分离为5个组分，并考察了各组分的影响。即使在CNF-HWSF中没有糖和氨基酸的组份D也有促进作用，从这些结果来看，CNF-HWSF的促进作用似乎是一个两步反应。第一步可以通过CNF-HWSF中的单糖、同源糖和游离氨基酸等丰富的营养物质来实现。第二步认为显著的促进作用是由胞外酶的刺激引起的。目前，以木屑为基料的CNF作为生长基质的实际应用尚处于完善阶段。进一步对CNF-HWSF中促进物质的分离和性质进行研究，以阐明其对食用菌的促进作用机制。

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.