Structure determination of two new sesquiterpenoids from Streptomyces sanglieri
Sesquiterpenoids are a group of abundant and structurally diverse secondary metabolites mainly derived from plant and fungi. By contrast, they are rarely isolated from bacteria, and the terpene synthase genes had been considered to be silent in prokaryotes. Recently, more and more terpenes were identified from bacteria, and the biosynthesis of some terpenes has been discussed in heterologous bacteria. Actually, it demonstrated that the terpene synthases are widely distributed in bacteria, including streptomycete, and some new sesquiterpenoids and diterpenoids had been obtained through heterologous expression of terpene synthase genes derived from Streptomyces microorganism. In our ongoing investigation of new bioactive natural products from streptomycete, two new sesquiterpenes, 15-hydroxy-(+)-epicubenol (1) and 7β-hydroxy-7-epi-α-eudesmol (2), were identified from a fermentation broth of Streptomyces sanglieri (YIM 121209-2), which was isolated from the forest soil sample collected from Wuyi Mountain, Fujian Province, China. The structures of compounds 1 and 2 (Fig. 1) were elucidated based on detailed spectroscopic data analyses, including 1D and 2D NMR techniques. The cytotoxicity against two human cancer cell lines and antimicrobial activity against a panel of bacteria and fungi of 1 and 2 were evaluated. None of them showed cytotoxic or antimicrobial activities at 100μg/ml.
Bacterial terpenome.
Covering: up to mid-2020Terpenoids, also called isoprenoids, are the largest and most structurally diverse family of natural products. Found in all domains of life, there are over 80 000 known compounds. The majority of characterized terpenoids, which include some of the most well known, pharmaceutically relevant, and commercially valuable natural products, are produced by plants and fungi. Comparatively, terpenoids of bacterial origin are rare. This is counter-intuitive to the fact that recent microbial genomics revealed that almost all bacteria have the biosynthetic potential to create the C5 building blocks necessary for terpenoid biosynthesis. In this review, we catalogue terpenoids produced by bacteria. We collected 1062 natural products, consisting of both primary and secondary metabolites, and classified them into two major families and 55 distinct subfamilies. To highlight the structural and chemical space of bacterial terpenoids, we discuss their structures, biosynthesis, and biological activities. Although the bacterial terpenome is relatively small, it presents a fascinating dichotomy for future research. Similarities between bacterial and non-bacterial terpenoids and their biosynthetic pathways provides alternative model systems for detailed characterization while the abundance of novel skeletons, biosynthetic pathways, and bioactivies presents new opportunities for drug discovery, genome mining, and enzymology.
Modeling of chemical reactors—XXIX mixing-cell model for packed bed reactors. Steady state considerations. Problems of multiplicity
Abstract The axial heat and mass transfer in tubular catalytic reactors may be described by mixing-cell model and diffusion model as well. The diffusion description yields for a strong exothermic reaction and adiabatic conditions three steady state profiles, on the other hand the mixing-cell model gives rise to more than three steady states. A simple numerical and graphical analysis for mixing-cell model is presented.