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Effects of additives on
cordycepin production using a Cordyceps militaris
mutant induced by ion beam irradiation
S. K. Das, M. Masuda, A.
Sakurai and M. Sakakibara*
Department of Applied Chemistry and Biotechnology,
Graduate School of Engineering, University of Fukui, Fukui
910-8507, Japan.
*Corresponding author. E-mail:
m-sakaki@u-fukui.ac.jp.
Accepted 23 June, 2009 |
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To obtain a
sustainable mutant of the medicinal mushroom Cordyceps
militaris with a higher cordycepin production,
high-energy ion beam irradiation was applied in the present
study. Upon successful irradiation by a proton beam, 30
classes of 8-azaadenine and 28 classes of 8-azaaguanine
resistant mutants were obtained of which 7 classes (A63-7,
A63-8, A81-2, A81-6, G63-8, G81-3, G82-4) were selected as
initially promising mutants using their antibacterial
ability as an index of cordycepin production. Among these
mutants, G81-3 had the highest cordycepin production of 6.84
g/l using optimized conditions compared to that of the
control of 2.45 g/l (2.79 times higher). In addition, to
explore the influences of different additives on the
cordycepin production using the above mutant in a surface
liquid culture, adenosine and glycine were used as
additives. In the culture medium under the previously
optimized conditions for the said mutant, 2, 4, 6, 8 and 10
g/l adenosine were separately added. These results revealed
the highest cordycepin production of 8.57 g/l when using 6
g/l adenosine was 28.10% higher than that of the control
(6.69 g/l). This is a highest report of cordycepin
production until now. Similarly, the results of other
concentrations also superseded the control. The time course
of glucose showed that the glucose consumption for the 4 g/l
adenosine was the fastest, while that of 10 g/l was the
slowest with the longest culture time among all the
treatments. For the same purpose, glycine was used with
yeast extract in weight percent ratios (yeast extract/glycine)
of 40/60, 50/50, 60/40, 70/30, 80/20 and 90/10 under the
condition that the total amount of glycine and yeast extract
were fixed. Also, the glycine was separately added as 10, 20
and 30 weight percent of yeast extract in the culture medium
having the same optimized conditions with a fixed yeast
extract concentration. These results showed that the 90/10
ratio had the best cordycepin production of 6.80 g/l that
was 12.40% higher versus the control (6.05 g/l). The
cordycepin production of the 70/30 and 80/20 weight percent
ratios were also higher than that of the control, while the
others had a lower cordycepin production compared to that of
the control; especially the cordycepin production with the
10, 20 and 30 weight percent yeast extracts inversely
decreased in accordance with the used glycine concentration.
Regarding the time course, the glucose consumption for the
40/60 weight percent ratio of yeast extract was the fastest,
while that of the 30 weight percent was the slowest with the
longest culture time among all the treatments. These results
suggested that both the ion beam irradiation and additives
had active influences on the cordycepin production and that
adenosine had a much better influence than that of glycine.
It was also evident that a higher concentration of both
adenosine and glycine negatively affected the cordycepin
production.
Key
words:
Ion
beam, cordycepin, Cordyceps militaris, mutant,
additives. |
