Microorganisms, secondary

Figure 2 Terrestrial plant and soil microorganism secondary metabolites currently used as drugs...

One possible reason for the existenee of stomach-cancer-producing soils is the production of cancer-causing secondary metabolites by plants and microorganisms. Secondary metabolites are biochemieal eompounds that are of no apparent use to the organism producing them. It is believed that they are formed from the precursors of primary metabolites when the primary metabolites accumulate to excessive levels. 

In secondary wastewater treatment plants receiving silver thiosulfate complexes, microorganisms convert this complex predominately to silver sulfide and some metallic silver (see Wastes, INDUSTRIAL). These silver species are substantially removed from the treatment plant effluent at the settling step (47,48). Any silver entering municipal secondary treatment plants tends to bind quickly to sulfide ions present in the system and precipitate into the treatment plant sludge (49). Thus, silver discharged to secondary wastewater treatment plants or into natural waters is not present as the free silver ion but rather as a complexed or insoluble species. 

The P-lactam antibiotics ate produced by secondary metaboHc reactions that differ from those responsible for the growth and reproduction of the microorganism. In order to enhance antibiotic synthesis, nutrients must be diverted from the primary pathways to the antibiotic biosynthetic sequences. Although most media for the production of penicillins and cephalosporins are similar, they ate individually designed for the specific requkements of the high yielding strains and the fermentation equipment used. 

The held of marine natural products chemistry, which encompasses the study of the chemical structures and biological activities of secondary metabolites produced by marine plants, animals, and microorganisms, began in earnest in the early 1960s. " This is in stark contrast to the study of terrestrial plant natural... 

The underlying assumption driving marine natural products chemistry research is that secondary metabolites produced by marine plants, animals, and microorganisms will be substantially different from those found in traditional terrestrial sources simply because marine life forms are very different from terrestrial life forms and the habitats which they occupy present very different physiological and ecological challenges. The expectation is that marine organisms will utilize completely unique biosynthetic pathways or exploit unique variations on well established pathways. The marine natural products chemistry research conducted to date has provided many examples that support these expectations. 

There have been only a few studies have evaluated membrane microfiltration of secondary wastewater effluent. Microfiltration membranes might be used to achieve very low turbidy effluents with very little variance in treated water quality. Because bacteria and many other microorganisms are also removed, such membrane disinfection might avoid the need for chlorine and subsequent dechlorination. Metal... 

In a typical plant operation the pollutants dissolved in the wastewater or that would not settle in the primary clarifiers flow on in the wastewater to the Secondary treatment process. Secondary treatment further reduces organic matter (BOD,) through the addition of oxygen to the wastewater which provides an aerobic environment for microorganisms to biologically break down this remaining organic matter. 

Biotechnological processes may be divided into fermentation processes and biotransformations. In a fermentation process, products are formed from components in the fermentation broth, as primary or secondary metabolites, by microorganisms or higher cells. Product examples are amino acids, vitamins, or antibiotics such as penicillin or cephalosporin. In these cases, co-solvents are sometimes used for in situ product extraction. 

Microorganisms have been identified and exploited for more than a century. The Babylonians and Sumerians used yeast to prepare alcohol. There is a great history beyond fermentation processes, which explains the applications of microbial processes that resulted in the production of food and beverages. In the mid-nineteenth century, Louis Pasteur understood the role of microorganisms in fermented food, wine, alcohols, beverages, cheese, milk, yoghurt and other dairy products, fuels, and fine chemical industries. He identified many microbial processes and discovered the first principal role of fermentation, which was that microbes required substrate to produce primary and secondary metabolites, and end products. 

Microbial Deracemization of Secondary Alcohols Using a Single Microorganism... 

It is well known that certain microorganisms are able to effect the deracemization of racemic secondary alcohols with a high yield of enantiomerically enriched compounds. These deracemization processes often involve two different alcohol dehydrogenases with complementary enantiospedficity. In this context Porto ef al. [24] have shown that various fungi, induding Aspergillus terreus CCT 3320 and A. terreus CCT 4083, are able to deracemize ortho- and meta-fluorophenyl-l-ethanol in good... 

An alternative approach to the microbial deracemization of secondary alcohols is to use two different microorganisms with complementary stereoselectivity. Fantin et al. studied the stereoinversion of several secondary alcohols using the culture supernatants of two microorganisms, namely Bacillus stearothermophilus and Yarrowia lipolytica (Figure 5.18) [31]. The authors tested three main systems for deracemization. First, they used the supernatant from cultures of B. stearothermophilus, to which they added Y. lipolytica cells and the racemic alcohols. Secondly, they used the culture supernatant of Y. lipolytica and added B. stearothermophilus cells and the racemic alcohols. Finally, they resuspended the cells of both organisms in phosphate buffer and added the racemic alcohols. The best results were obtained in the first system with 6-penten-2-ol (26) (100% ee and 100% yield). The phosphate buffer system gave... 

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