Abstract
A Vitreoscilla hemoglobin (VHb) gene was efficiently expressed by the optimization of codons and intron addition in G. lucidum. Expression of the VHb gene was confirmed by genome PCR, quantitative real-time PCR and carbon monoxide (CO)-difference spectrum analysis in the transformant. The effects of the efficient expression of VHb gene on production, monosaccharide compostion, and antioxidant activity of G. lucidum exopolysaccharides were studied. The maximum production of exopolysaccharides in the VHb gene-bearing transformant was 1.63 g/L, which was 1.5-fold higher than expression in the wild-type strain. Efficient expression of the VHb gene did not change the monosaccharide composition or distribution of molecular weight, but it increased the mole percentage ratio of galactose and mannose in G. lucidum exopolysaccharide. Exopolysaccharides from the transformant had higher scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl (OH) radical capacity and reducing power than those from the wild-type strain. These results may be helpful for increasing production and application of exopolysaccharides produced by G. lucidum fermentation.
Highlights
Ganoderma lucidum is a medicinal mushroom that has been used in Asia for more than 2000 years to treat various diseases [1]
The codon-optimized Vitreoscilla hemoglobin (VHb) gene was regulated by the gpd promoter and the succinate dehydrogenase gene terminator of G. lucidum
We examined effects of opvhb expression on the molecular weight (Mw) distribution of exopolysaccharides obtained from the WT and OPVHB strains under liquid shaking of exopolysaccharides obtained from the WT and OPVHB strains under liquid shaking culture conditions
Summary
Ganoderma lucidum is a medicinal mushroom that has been used in Asia for more than 2000 years to treat various diseases [1]. Polysaccharides are active constituents of G. lucidum [3] that possess many kinds of bioactivities such as antioxidant, anti-aging, anti-inflammatory, immunomodulation, and antitumor bioactivities [4]. High production of G. lucidum exopolysaccharides is required to meet commercial demands. Many approaches have been developed to increase the production of G. lucidum exopolysaccharides. These include the optimization of media and fermentation conditions [5,6,7], addition of elicitor [8,9], development of new bioprocessing strategies [10,11], and genetic engineering of G. lucidum [12,13]
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