Fed-batch fermentation of Tuber melanosporum for the hyperproduction of mycelia and bioactive Tuber polysaccharides.

For the first time, a fed-batch fermentation process of Tuber melanosporum was developed for the efficient production of bioactive mycelia and Tuber polysaccharides. Each 1.67 g/L of peptone and 8.33 g/L of yeast extract were added on day 3, 6, and 9, respectively, and sucrose was fed to maintain its concentration around 35-5 g/L when its residual level decreased to 10-5 g/L. Then, the maximal biomass, the production of extracellular polysaccharides (EPS) and intracellular polysaccharides (IPS) reached 53.72+/-2.57 g DW/L, 7.09+/-0.62 and 4.43+/-0.21 g/L, respectively. Compared with the batch culture conducted in the enriched medium, the biomass, the production of EPS and IPS were enhanced by 55.8%, 222.3% and 103.2%, respectively. Not only the cell density but also the production of EPS and IPS were the highest ever reported in truffle fermentation, and the biomass was also the highest as ever reported in mushroom fermentation.

Novel biotransformation process of podophyllotoxin to produce podophyllic acid and picropodophyllotoxin by Pseudomonas aeruginosa CCTCC AB93066, part II: process optimization.

This work optimized the novel biotransformation process of podophyllotoxin to produce podophyllic acid by Pseudomonas aeruginosa CCTCC AB93066. Firstly, the biotransformation process was significantly affected by medium composition. 5 g/l of yeast extract and 5 g/l of peptone were favorable for podophyllic acid production (i.e. 25.3+/-3.7 mg/l), while not beneficial for the cell growth of P. aeruginosa. This indicated that the accumulation of podophyllic acid was not corresponded well to the cell growth of P. aeruginosa. 0 g/l of sucrose was beneficial for podophyllic acid production (i.e. 34.3+/-3.9 mg/l), which led to high podophyllotoxin conversion (i.e. 98.2+/-0.1%). 1g/l of NaCl was the best for podophyllic acid production (i.e. 47.6+/-4.0mg/l). Secondly, the production of podophyllic acid was significantly enhanced by fed-batch biotransformation. When each 100mg/l of podophyllotoxin was added to the biotransformation system after 4, 10 and 25 h of culture, respectively, podophyllic acid concentration reached 99.9+/-12.3mg/l, enhanced by 284% comparing to one-time addition (i.e. 26.0+/-2.1mg/l). The fundamental information obtained in this study provides a simple and efficient way to produce podophyllic acid.

Quantitative response of cell growth and Tuber polysaccharides biosynthesis by medicinal mushroom Chinese truffle Tuber sinense to metal ion in culture medium.

During the submerged fermentation of medicinal mushroom Chinese truffle Tuber sinense, there was no significant effect of metal ion on the cell growth and the production of intracellular polysaccharides, while metal ion and its concentration significantly affected the production of extracellular polysaccharides (EPS). By using the approach of "one-variable-at-a-time", 50 mM Mg2+ was identified to be the most favorable for EPS production, and the next was 10 mM K+. A mathematical model, constructed by response surface methodology combination with full factorial design, was applied to study the synergic effect of Mg2+ and K+. EPS production reached its peak value of 5.86 g/L under their optimal combination of 30 mM Mg2+ and 5 mM K+ predicted by the model, which was higher by 130.7% compared with the basal fermentation medium without metal ion. The validation experiment showed the experimental values agreed with the predicted values well. EPS production obtained in this work was the highest reported in the culture of T. sinense.