Efficient snailase-based production of mogrol from Luo Han Guo extract in an aqueous-organic system.

To solve the insufficient availability of mogrol, an 11α-hydroxy aglycone of mogrosides in Siraitia grosvenorii, snailase was employed as the enzyme to completely deglycosylate LHG extract containing 50% mogroside V. Other commonly used glycosidases performed less efficiently. Response surface methodology was conducted to optimize the productivity of mogrol, which peaked at 74.7% in an aqueous reaction. In view of the differences in water-solubility between mogrol and LHG extract, we employed an aqueous-organic system for the snailase-catalyzed reaction. Of five tested organic solvents, toluene performed best and was relatively well tolerated by snailase. After optimization, biphasic medium containing 30% toluene (v/v) could produce a high-quality mogrol (98.1% purity) at a 0.5 L scale with a production rate of 93.2% within 20 h. This toluene-aqueous biphasic system would not only provide sufficient mogrol to construct future synthetic biology systems for the preparation of mogrosides, but also facilitate the development of mogrol-based medicines.

Enzymatic hydrolyzation of mogrosides in Luo Han Guo extract by NKA-adsorbed snailase improves its sensory profile.

Extracts of Siraitia grosvenorii (Swingle), in Chinese known as Luo Han Guo (LHG), is authorized for use as a natural sweetener. LHG is rich in mogroside V that contains five glucoses, but also contains mogroside IIIE and analogues with fewer than three glucose units that cause an unpleasant aftertaste, limiting the use of the extract. Snailase was applied here to convert mogroside V in LHG extract in favor of siamenoside I formation, the sweetest mogroside with a taste similar to sucrose. For application, snailase was immobilized by adsorption to NKA (a macroporous resin), resulting in 10.9 U per g of adsorbed protein. Reuse of the NKA-adsorbed snailase was demonstrated for four cycles, and a continuous production of improved LHG extract at a 0.5 L scale had a productivity of 68.4 g/(L⋅day). The resulting product containing over 50% siamenoside I displayed an improved taste profile with satisfying safety toward HEK293T cells.

Optimization of critical medium components for enhancing antibacterial thiopeptide nocathiacin I production with significantly improved quality.

Nocathiacin I, a glycosylated thiopeptide antibiotic, displays excellent antibacterial activities against multidrug resistant bacterial pathogens. Previously, a novel nocathiacin I formulation for intravenous administration has been successfully developed and its aqueous solubility is greatly enhanced for clinical application. The purpose of the present study was to increase the fermentation titer of nocathiacin I and reduce or eliminate analogous impurities by screening the medium ingredients using response surface methodology. After a sysmatic optimization, a water-soluble medium containing quality-controllable components was developed and validated, resulting in an increase in the production of nocathiacin I from 150 to 405.8 mg·L-1 at 150-L scale. Meanwhile, the analogous impurities existed in reported processes were greatly reduced or eliminated. Using optimized medium for fermentation, nocathiacin I with pharmaceutically acceptable quality was easily obtained with a recovery of 67%. In conclusion, the results from the present study offer a practical and efficient fermentation process for the production of nocathiacin I as a therapeutic agent.

The importance of start codon of nosM in nosiheptide production.

The present study was designed to investigate the effects of start codon of nosM on the biosynthesis of nosiheptide. Target genes were amplified by overlap PCR. After homologous recombination to construct engineered strains, nosiheptide production was analyzed by HPLC. Three mutants with different start codon of nosM were constructed, and nosiheptide production of each mutant was analyzed and compared. Replacement of the start codon of nosM significantly decreased the production of nosiheptide. In conclusion, start codon usage could greatly affect the biosynthetic efficiency in the biosynthetic gene cluster of nosiheptide.