Abstract

The effects of several metal ions on the cell growth, production of polysaccharides by Ganoderma lucidum in submerged fermentation were studied. The results showed that 50 ppm Se²⁺ and 25 ppm Se²⁺ was identified to be the most favorable for biomass (11.103 ± 0.6 g/l ) and polysaccharide production (IPS and EPS was 183 ± 10.2 and 248 ± 5.5 mg/l, respectively); 100 ppm of Fe²⁺ and 50 ppm of Zn²⁺were suitable for growth (the biomass was 8.23 ± 0.67 and 8.01 ± 0.29 g/l, respectively) and under the concentration of 50 ppm of Zn²⁺ and Fe²⁺, the production of polysaccharide was up to the most (EPS content: 263±4 and 254.3±8.0 mg/l; IPS content : 170±0.8 and 174±5 mg/l); Mg²⁺ had no obvious effect on biomass and polysaccharide production; Cr²⁺ was poisonous to the cell under the test concentration. The combination (FeSO₄, 50 ppm; NaSeSO₃, 25 ppm; ZnSO₄, 75 ppm) by A 9 ×3 replicates (27) experiments of L9 (3⁴) orthogonal projects was tested optimal for the cell growth and polysaccharides production. Biomass, EPS and IPS production reached their good value of 14.7 ± 0.5 g/l, 369 ± 6 mg/l and 239 ± 4 mg/g, respectively under the combination, which were higher 130.7, 50 and 50%, respectively than in the basal fermentation medium without metal ions. The validation experiment showed the experimental values agreed with the predicted values well (error <1%).

Key words: Ganoderma lucidum, metal ions, biomass, polysaccharide, orthogonal projects.