Thailandepsin A is natural product of Burkholderia thailandensis E264 with potent histone deacetylase inhibitory activities and promising anticancer activities. The titer of thailandepsin A is very low (less than 10 mg/l) from limited empirical fermentation. To facilitate preclinical evaluations and potentially clinical development of thailandepsin A, systematic optimization and extractive fermentation of thailandepsin A from B. thailandensis E264 culture in flasks were investigated in this pilot study. The main fermentation parameters--28°C, pH 7.0, inoculum ratio 1% (v/v), incubation duration 60 h, medium volume 26%, shaking speed 170 rpm, and chloroform as extracting solvent--were determined by single factor experiments. Polyaromatic adsorbent resin Diaion HP-20, when added at a concentration of 4% (w/v), was most effective to reduce feedback inhibition of thailandepsin A and to significantly increase the titer of target product. Central composite design was used to further optimize the fermentation medium for B. thailandensis E264. The optimized medium contains glucose 17.89 g/l, tryptone 34.98 g/l, potassium phosphate 24.84 g/l, and sodium citrate 0.01 g/l, which resulted in a large increase of the titer of thailandepsin A to 236.7 mg/l. Finally kinetic models based on the modified logistic and Luedeking-Piret equations were developed, delivering a good description of temporal variations of biomass, product, and substrate in the fermentation process, which could be used as references for developing large-scale fermentation.

Strain Y1B was isolated from a soil sample collected from Wuxi in Jiangsu Province, China. The strain was identified as Streptomyces griseoruber based on phenotypic characteristics and 16S rRNA gene sequence analysis. phzE and phzF gene fragments were amplified by PCR from S. griseoruber Y1B, and showed 70-80% similarity to those of phenazine-producing Pseudomonas and Streptomyces species, indicating that this strain contained phenazine biosynthetic genes and had the potential to produce phenazine compounds. A crude extract, obtained from S. griseoruber Y1B fermentation broth by organic solvent extraction and evaporation under reduced pressure, showed significant antifungal activity against Rhizoctonia solani, Pythiumultimum, and Fusarium oxysporum, and had a broad spectrum of antifungal activity. A phenazine compound, 1-hydroxyphenazine, and a shikimic acid-derived metabolite, benzoic acid, were separated and purified from the crude extract by preparative high performance liquid chromatography. The effects of addition of intermediate metabolites on 1-hydroxyphenazine production implied that the phenazine biosynthesis pathway in S. griseoruber Y1B might branch off from the shikimate pathway, using phenazine-1-carboxylic acid as the phenazine precursor. Furthermore, this is the first demonstration that S. griseoruber can produce phenazine compounds. Therefore, as a novel Streptomyces strain, S. griseoruber Y1B might have potential applications for biocontrol in agricultural production.