Isolation of new microbial

Isolation of New Microbial Metabolites. Surprisingly, this discovery approach is placed on a par with chemical modification of useful antibiotics as the most promising for the next decade (Table VII). This is... 

For many years, one way to solve these drawbacks has been the identification and isolation of new biocatalysts with the desired characteristics. The most common procedure for isolation and identification of biocatalysts has also been applied to microbial populations living in harsh environments such as hot springs, abyssal hot vents or geothermal power plants. These microorganisms, known as extremophiles can be foimd in environments of extreme temperature, ionic strength, pH, pressure, metal concentrations or radiation levels. These natural reservoirs of extremozymes directly offer new activities and extreme stabilities but these microorganisms also offer novel metabolic pathways. Table 10.11 summarizes the identified extremoz5mies found in some extremophiles. 

Studies of microbial transformations of bruceantin (53) led to the isolation of new analogs of this antitumor quassinoid (70). Thus, Streptomyces griseus (ATCC 10137) totally metabolized bruceantin (53) within 19 h, and a preparative scale incubation using bruceantin provided brucein C (51), bruceantin-4, 5 -epoxide and bruceantin-5 -ol. None of the metabolites were as active as bruceantin in the P388 test system (70). 

Traditionally, the majority of the studies in this area have emphasized the analysis of microorganisms, in particular of soil actinomycetes, as the most relevant source of potential herbicide agents. The plant kingdom, however, has also been explored for the discovery of new herbicides. So far, bialaphos, originally isolated from different Streptomyces strains, is the only commercial herbicide derived from a microbial source. On the other hand, cymethylin, an analog of the mono terpenoid 1,8-cineole, as well as... 

McKee, T.C. et ah. Isolation and characterization of new anti-HIV and cytotoxic leads from plants, marine, and microbial organisms, J. Nat. Prod., 60, 431, 1997. 

Microbial bioconversion studies of manzamine A and ent-8-hydroxymanzamine A have shown that they can be metabolized by several microbial species.76 Preparative-scale fermentation of manzamine A with Fusarium oxysporium f. gladioli ATCC 11137 resulted in the isolation of the known ircinal A (61) as a major metabolite. Preparative-scale fermentation of enf-8-hydroxymanzamine A with Nocardia sp. ATCC 11925 and Fusarium oxysporium ATCC 7601 resulted in the isolation of the new major metabolite 12,34-oxamanzamine F (62). The latter metabolite showed no cytotoxicity against different cell lines (>10 pg/ml). 

---