Pseudomonas taetrolens

Musty or potato-like flavor and aroma have been observed as a defect in milk (Hammer and Babel 1957) and Gruyere de Comte cheese (Dumont et al. 1975). This off-flavor results from the production of nitrogenous cyclic compounds by Pseudomonas taetrolens and P. perolens (Morgan 1976). Musty-flavored compounds produced by these organisms include 2,5-dimethylpyrazine and 2-methoxy-3-isopropyl-pyrazine. The Gruyere de Comte with potato off-flavor contained 3-methoxy-2-propyl pyridine, as well as alkyl pyrazine compounds (Dumont et al. 1975). Murray and Whitfield (1975) postulated that alkyl pyrazines are formed in vegetables by condensation of amino acids such as valine, isoleucine, and leucine with a 2-carbon compound. Details of the synthetic mechanism in pseudomonads are unknown. 

Yamamoto, S., M. Wakayama, and T. Tachiki. 2005. Theanine production by coupled fermentation with energy transfer employing Pseudomonas taetrolens Y-30 glutamine synthetase and baker s yeast cells. Biosci. Biotechnol. Biochem. 69 784-789. 

Pyrazines are also produced by microorganisms. For example, 2-isopropyl-3-methoxypyrazine has been identified as a metabolic byproduct of Pseudomonas perolans and Pseudomonas taetrolens. This pyrazine is responsible for a musty/earthy off-flavor in eggs, dairy products and fish. 

A pyruvate aldolase from Pseudomonas taetrolens catalyzes the aldol addition of pyru-vafe to indole-pyruvic acid (34), a ketone [85]. This is an interesting example of an aldolase fhaf cafalyzes an aldol addition to a ketone acceptor. A variant of this aldolase was used in fhe stereoselective synfhesis of a precursor (35) of monatin (36), whose 2R,4R stereoisomer is 2700-fold sweeter fhan sucrose (Scheme 10.3) [86]. 

Enzymatic synthesis of a precursor of monatin (36) using pyruvate-dependent aidoiases from Pseudomonas taetrolens (PyAp... 

MGL catalyzes the o ,7-elimination reaction of methionine to a-ketobutyrate, methanethiol, and ammonia. MGL has been isolated from a number of bacteria, including Pseudomonas putida, Aeromonas sp., Clostridium sporogenes, P. taetrolens, and Brevibacterium linens, from the primitive protozoa Entamoeba histolytica and Trichomonas vaginalis, but is not believed to be present in yeast, plants, or mammals. " " Two MGL isoforms have been isolated from T. vaginali and Entamoeba histolytica, which differ in substrate specificity, overall charge, and catalytic properties. They show a high degree of sequence identity to MGL from Pseudomonas putida. MGL has demonstrated antitumor efficacy in a number of methionine-dependent cancer cell lines. ... 

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