| Summary: | 博士 === 國立中興大學 === 化學工程學系所 === 96 === Grifola umbellata is one of the most famous traditional Chinese medicinal mushrooms and has also been termed as Polyporus umbellatus or Chuling in scientific reports. The fruiting bodies of G. umbellata are commonly used for treating edema and promoting diuretic process. It has been reported that G. umbellata possesses outstanding anti-tumor effects. In light of its health benefits, G. umbellata of various compositions could be used as medicinal mushroom in the global market. Owing to inefficient protection, the wild sources of Grifola umbellata have been seriously depleted. To meet the mass demand of global market, it is necessary to cultivate the strain of Grifola umbellata under artificial conditions. However, the production of fruiting bodies of Grifola umbellata from field cultivation is a time-consuming and labor-intensive process. Meanwhile, the quality of G. umbellata under soil cultivation is difficult to control. Therefore, submerged fermentation for mycelia culture has recently received great interest as a promising alternative for efficient production. The study contains four parts.
In the first part, a brownish Grifola umbellata broth concentrate (GBC) harvested at the beginning of the growth phase was collected and used as an additive in the medium to investigate its effect on facilitating mycelia germination. The results showed that the addition of GBC in solid-state culture promoted mycelia growth. Moreover, the GBC addition in submerged culture significantly shortened the lag phase and the maximum mycelia production was enhanced by 18 %, from 10.8 g/l to 12.78 g/l. These results demonstrate that GBC is capable of stimulating Grifola umbellata growth in all respects.
In the second part, the effects of cultural condition on the mycelial growth and exopolysaccharide (EPS) production were studied. The results showed that glucose was the best carbon source for mycelia growth and EPS production. Yeast extract was the best nitrogen source for mycelia growth, whereas skim milk as nitrogen source can remarkably improve EPS production. The optimal medium constituents for EPS production were as follows: glucose 3%, skim milk 0.2%, 0.1% KH2PO4, 0.1% MgSO4、7H2O, 0.005% Vitamin B1. The initial pH value of 5 was the most efficient to EPS production. The Grifola umbellata culture with skim milk as nitrogen source displayed a much higher specific EPS yield of 112.35 mg/g, accounting for a 4.36 times increase compared to that with combined nitrogen source medium.
In the third part, several different additives were supplied in the cultural medium to find the one with the most stimulatory effect on G. umbellata mycelia growth and exopolysaccharide production. The results show that polyethylene glycol PEG (Mw 8000Da) is the most effective stimulator. With its addition, the maximum mycelia production at day 14 was enhanced from 5.236 g/l to 6.316 g/l, accounting for a 21% increase. Meanwhile, the exopolysaccharide production was enhanced from 0.484 g/l to 0.769 g/l at day 12, accounting for a 59 % increase.
Finally, a novel approach to utilizing whey, the cultivation of mycelial growth and exopolysaccharide production by medicinal mushroom Grifola umbellata is introduced. The result shows that whey could be an alternative substrate for mycelia growth and polysaccharide production. Therefore, cultivation of Grifola umbellata mycelia and exopolysaccharide production using whey can provide a unique solution to solve the dual problems of an alternative utilization of the whey and waste management.
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