- Enhanced Production of Exopolysaccharides by Fed-batch Culture of Ganoderma resinaceum DG-6556
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Hyun Mi Kim , Soon-Young Paik , Kyung Soo Ra , Kwang Bon Koo , Jong Won Yun , Jang Won Choi
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J. Microbiol. 2006;44(2):233-242.
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DOI: https://doi.org/2360 [pii]
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 Abstract
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The objectives of this study were to optimize submerged culture conditions of a new fungal isolate, Ganorderma resinaceum, and to enhance the production of bioactive mycelial biomass and exopolysaccharides (EPS) by fed-batch culture. The maximum mycelial growth and EPS production in batch culture were achieved in a medium containing 10 g/l glucose, 8 g/l soy peptone, and 5 mM MnCl2 at an initial pH 6.0 and temperature 31°C. After optimization of culture medium and environmental conditions in batch cultures, a fed-batch culture strategy was employed to enhance production of mycelial biomass and EPS. Five different EPS with molecular weights ranging from 53,000 to 5,257,000 g/mole were obtained from either top or bottom fractions of ethanol precipitate of culture filtrate. A fed-batch culture of G. resinaceum led to enhanced production of both mycelial biomass
and EPS. The maximum concentrations of mycelial biomass (42.2 g/l) and EPS (4.6 g/l)
were obtained when 50 g/l of glucose was fed at day 6 into an initial 10 g/l of glucose
medium. It may be worth attempting with other mushroom fermentation processes for
enhanced production of mushroom polysaccharides, particularly those with industrial
potential.
- The Influence of the Nucleotide Sequences of Random Shine-Dalgarno and Spacer Region on Bovine Growth Hormone Gene Expression
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Soon-Young Paik , Kyung Soo Ra , Hoon Sik Cho , Kwang Bon Koo , Hyung Suk Baik , Myung Chul Lee , Jong Won Yun , Jang Won Choi
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J. Microbiol. 2006;44(1):64-71.
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DOI: https://doi.org/2335 [pii]
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Abstract
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To investigate the effects of the nucleotide sequences in Shine-Dalgarno (SD) and the spacer region
(SD-ATG) on bovine growth hormone (bGH) gene expression, the expression vectors under
the control of the T7 promoter (pT7-7 vector) were constructed using bGH derivatives (bGH1 &
bGH14) which have different 5''-coding regions and were induced in E. coli BL21(DE3).
Oligonucleotides containing random SD sequences and a spacer region were chemically synthesized
and the distance between the SD region and the initiation codon were fixed to nine bases
in length. The oligonucleotides were annealed and fused to the bGH1 and bGH14 cDNA,
respectively. When the bGH gene was induced with IPTG in E. coli BL21(DE3), some clones containing
only bGH14 cDNA produced considerable levels of bGH in the range of 6.9% to 8.5%
of total cell proteins by SDS-PAGE and Western blot. Otherwise, the bGH was not detected in
any clones with bGH1 cDNA. Accordingly, the nucleotide sequences of SD and the spacer region
affect on bGH expression indicates that the sequences sufficiently destabilize the mRNA secondary
structure of the bGH14 gene. When the free energy was calculated from the transcription initiation
site to the +51 nucleotide of bGH cDNA using a program of nucleic acid folding and hybridization
prediction, the constructs with values below ‒26.3 kcal/mole (toward minus direction)
were not expressed. The constructs with the original sequence of bGH cDNA also did not show
any expression, regardless of the free energy values. Thus, the disruption of the mRNA secondary
structure may be a major factor regulating bGH expression in the translation initiation process.
Accordingly, the first stem-loop among two secondary structures present in the 5''-end region of
the bGH gene should be disrupted for the effective expression of bGH.
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