| A strategy that optimization of medium compositions for maximum biomass followed by feeding of sucrose for maximum polysaccharide synthesis was developed for enhancing polysaccharide production in suspension culture of protocorm-like bodies (PLBs) of Dendrobium huoshanense C.Z. Tang et S.J. Cheng. In growth stage, the original half-strength MS medium was optimized with carbon sources, nitrogen sources and metal ion combinations. The effects of different carbon sources on PLBs growth were remarkable and sucrose at 35 g l-1 was the most suitable. Sole nitrate nitrogen of 30 mmol l-1 was the best for PLBs growth. Metal ions (Ca2+, Fe2+, Mn2+ and Zn2+) showed different influences on PLBs growth. The optimal concentration of Ca2+, Fe2+, Mn2+ and Zn2+ was 4.5 mmol l-1, 0.1 mmol l-1, 0.5 mmol l-1 and 0.06 mmol l-1, respectively. In the optimized medium (sucrose, nitrate, Ca2+, Fe2+, Mn2+ and Zn2+ concentration as described above, the other component concentration seen in half-strength MS), 33.9 g DW l-1 PLBs were harvested after 30 days of culture and biomass increase was improved 245% as compared with that in the original medium. In production stage, polysaccharide synthesis was significantly improved by the feeding sucrose. The maximum polysaccharide production (22 g l-1) was obtained in the case of 50 g l-1 sucrose feeding at day 30 of culture, which was about 109-fold higher than that in the original medium without feeding of sucrose. |