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Optimization of mycelium
biomass and exopolysaccharides production by Hirsutella
sp. in submerged fermentation and evaluation of
exopolysaccharides antibacterial activity
Rong Li 1,2*,
Xiao-lu Jiang1 and Hua-shi Guan1
1College
of Food Science and Engineering, Ocean University of China,
Qingdao 266003, China.
2School
of Medicine and Pharmaceutics, Ocean University of China,
Qingdao 266003, China.
*Corresponding author. E -mail:
lirong1011@gmail.com.
Tel: +86 532 82032290. Fax: +86 532 82032389.
Accepted
8 September, 2009 |
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Hirsutella
is a hyphomycete that has been used as biopesticide. Many
compounds with antimycobacterial activity have been
reported. However, there were fewer reports about
fermentation condition for the Hirsutella and
activity of its exopolysaccharides. In the present
investigation, the fermentation condition and medium for
mycelia growth and exopolysaccharides production were
optimized and the antibacterial activity of
exopolysaccharides (EPS) from Hirsutella sp. was
studied. The optimized conditions and medium were as
follows: initial pH 5.5, potato extract 20% (w/v), sucrose
2.5%, peptone 0.5%, K2HPO4 0.2%, MgSO4
0.05% and fermentation for 4 days. The highest production of
EPS and mycelium biomass yield reached 2.17 and 10.06 g/l,
respectively. The content of sugar and protein of EPS were
92.7 and 5.2%, respectively. The monosaccharide component of
EPS was mannose, galactose and glucose with a molar ratio of
4.0:8.2:1.0. Its molecular weight was 23 kDa. The
antibacterial effect of EPS was observed that they were most
effective against gram-positive bacterium, especially
Bacillus subtilis and Micrococcus tetragenus. The
MIC of exopolysaccharides to B. subtilis and M.
tetragenus was 1 and 2.5 mg/ml, respectively. These
results are helpful to expand the application of
Hirsutella sp. as a biological pesticide.
Key
words:
Hirsutella sp., exopolysaccharides, mycelium
biomass, antibacterial activity. |
