Dong-Sheng Li

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.

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.

Design and synthesis of the novel DNA topoisomerase II inhibitors: esterification and amination substituted 4'-demethylepipodophyllotoxin derivates exhibiting anti-tumor activity by activating ATM/ATR signaling pathways.

According to the structure-activity relationship, drug combination principle and bioisosterism, a series of the novel esterification and amination 4-demethylepipodophyllotoxin derivates were rationally designed in order to discover the potential antitumor prodrug. And then these compounds were tested by the drug-topoisomerase II docking models for virtual screening. Thus, twelve target compounds were screened out and synthesized. Most of compounds exhibited promising in vitro anti-tumor activity, particularly 4-N-tris(hydroxymethyl)metylaminomethane-4-deoxy-4-demethylepipodophyllotoxin (Compound 1). The anti-tumor activity of Compound 1 against the tumor cell lines BGC-823 (i.e., the IC50 value of 5.35 ± 0.77 μM), HeLa (i.e., the IC50 value of 160.48 ± 14.50 μM), and A549 (i.e., the IC50 value of 13.95 ± 5.41 μM) was significantly improved by 706%, 31% and 900% than that of etoposide (i.e., the IC50 values of 43.74 ± 5.13, 209.90 ± 13.42, and 139.54 ± 7.05 μM), respectively. Moreover, the IC50 value of Compound 1 against the normal human cell line HK-2 (i.e., 16.3 ± 3.77 μM) was 78% lower than that of etoposide (i.e., 9.17 ± 1.58 μM). Compound 1 could diminish the relaxation reaction topoisomerase II DNA decatenation at a concentration of 10 μM and induce BGC-823 apoptosis by breaking DNA double-strand and activating ATM/ATR signaling pathways.

Supplementations of ornithine and KNO3 enhanced bacitracin production by Bacillus licheniformis LC-11

During the fermentative process of Bacillus licheniformis LC-11, the dissolved oxygen (DO) and ornithine (Orn) content in the medium fell to zero, indicating that they were the potential limiting factors for cell growth and/or bacitracin biosynthesis. In addition, given that the nitrate-reducing system existing in B. licheniformis could favor cell anaerobiosis, the impacts of KNO3 and Orn supplementations were therefore evaluated for improving bacitracin production in both a shaking flask and a 10-L fermentor. Orn supplementation (0.04xa0g/L) at 16xa0h or KNO3 addition (0.5xa0g/L) in the production medium enhanced bacitracin production by 5.8 and 3.7xa0%, respectively. The combined effects of KNO3 and Orn supplementations were then conducted via a two-level central composite design, resulting in a predicted maximum bacitracin yield of 821.81xa0U/mL if KNO3 and Orn were supplemented at 514.39xa0mg/L and 45.35xa0mg/L, respectively. This predicated yield was then verified experimentally in a 10-L fermentor, achieving a 10.8xa0% increased bacitracin production (825xa0U/mL) over that of the control.

Biotin enhances salt tolerance of Torulopsis mogii

Halophilic aromatic yeasts, such as Torulopsis mogii and Zygosaccharomyces rouxii, are usually used for soy sauce fermentation, in order to enhance the flavor and quality of the high-salt oriental food seasoning sauce. However, in the process of soy sauce brewing, salt stress affects the cell growth of the aromatic yeasts and extends the fermentation process. The tolerance to high NaCl concentrations is important for Torulopsis to produce flavor in soy sauce. In this study, we report that supplementation of biotin improved cell growth of T. mogii at high salt environment. Further studies suggested that biotin enhanced the osmotic tolerance (salt tolerance) of T. mogii through accumulating trehalose in cells, increasing the ratio of K+/Na+; promoting the activity of ATPase, and increasing the synthesis of fatty acids with long chain and high saturation. These results indicated that biotin could be an effective supplement for improvement of soy sauce fermentation.