Bacteria surfactants produced

New surfactants produced both by biosynthesis [4] and by synthesis are now being tested along with conventional synthetic surfactants. In this respect, cationics on the basis of arginine, which show a high inhibiting power to staphylococci, streptococci and other bacteria, are of special interest as bactericidal compositions [127]. 

The bacteria apparently produce some kind of diffusible substance. Extracts from bacterial cultures were fractionated and a compound highly effective in inhibiting fungal growth was isolated. The pure compound was active on its own and it was shown to be a new substance, viscosinamide. The compound is a cyclic peptide Fig 5.2 with a lipid tail and has strong surfactant properties (amphiphatic molecule). The compound is similar to other compounds that have been shown to create holes in membranes. 

One recent attempt to decrease the costs associated with surfactant flooding has been to inject surfactant-producing bacteria into oil reservoirs. This technique involves the injection of selected microorganisms into the reservoir and the subsequent stimulation and transportation of their growth products in order to recover more of the oil-in-place [34]. Some of the mechanisms proposed by which these microbes can stimulate oil production include reservoir repressurization, modification of reservoir rock, degradation and alteration of oil, decrease of viscosity, and increase in emulsification [35]. 

Yeast and bacteria can produce biosurfactants, biological surfactants from various substrates including sugars, oils, alkanes and wastes [5]. Some types of biosurfactants are glycolipids, lipopeptides, phospholipids, fatty acids, neutral lipids, polymeric and particulate compounds [6]. Most are either anionic or neutral, while only a few with amine groups are cationic. The hydrophobic part of the molecule is based on long-chain fatty acids, hydroxy fatty acids or a-alkyl-jS-hydroxy fatty acids. The hydrophilic portion can be a carbohydrate, amino acid, cyclic peptide, phosphate, carboxylic acid or alcohol. 

Considerable interest arose during the 1970 s and 1980 s in the use of micro-organisms to produce useful fatty adds and related compounds from hydrocarbons derived from the petroleum industry. During this period, a large number of patents were granted in Europe, USA and Japan protecting processes leading to the production of alkanols, alkyl oxides, ketones, alkanoic adds, alkane dioic acids and surfactants from hydrocarbons. Many of these processes involved the use of bacteria and yeasts associated with hydrocarbon catabolism. 

Many bacteria produce surfactants in response to exposure to hydrocarbons, and these have been demonstrated both for those that degrade alkanes and PAHs (Deziel et al. 1996). The positive effect of adding surfactants is, however, equivocal (Deschenes et al. 1996). 

Figure 4 Stabilized bromine antimicrobials are produced by eosinophils, a type of mammalian white blood cell. Bacteria are captured by phagocytosis and contained intracellularly within vesicles called phagosomes. Granules release cationic surfactants, lytic enzymes, and eosinophil peroxidase into the phagosome in a process known as degranulation. Eosinophil peroxidase, an enzyme that is structurally similar to the bromoperoxidases found in seaweed (Figure I), selectively catalyzes oxidation of bromide to hypobromite by reducing hydrogen peroxide to water. The hypobromite immediately reacts with nitrogenous stabilizers such as aminoethanesulfonic acid (taurine) to form more effective and less toxic antimicrobial agents.

The bacteria Pseudomonas syringae pv. tagetis, which is pathogenic to Jerusalem artichoke (Shane and Baumer, 1984), can apparently be used to repress weed populations. Spray applications of the organism (5 x 10s cells-mL1) in aqueous buffer with a non-ionic organosilicone surfactant (e.g., Silwet L-77 or Silwet 408), the latter being essential for infection, are said to produce severe disease symptoms, although no data were shown (Johnson et al., 1996). 

Determinations of mycobactin production by saprophytic and parasitic species of mycobacteria showed that saprophytic fast-growing mycobacteria produce more mycobactin than parasitic slow-growing mycobacteria (11). The extraction of virulent and avirulent strains of M. tuberculosis with surfactants showed that they contain similar amounts of mycobactin on their surfaces (9). Recently we have measured the production of enterochelin in IPM (0.09 / g iron/ml) by virulent strain C and avirulent strain A of E. coli (32). Results showed that spent media of virulent and avirulent bacteria contain similar amounts of enterochelin. The possibility remains, however, that still smaller amounts of iron in synthetic medium may stimulate virulent cells to produce more enterochelin. 

However, the use of anionic surfactants to control sulfide oxidation is limited because (1) they are very soluble and move with water, (2) they may be adsorbed on the surfaces of other minerals and may not reach the pyrite-bacteria interface (Erickson and Ladwig, 1985 Shellhorn and Rastogi, 1985), and (3) bactericides do not have much effect on acid-metallic drainages produced prior to treatment. 

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