Emulsifier/biosurfactant

Upgrading Biomass enzymatic work for non-food uses of the biomass (new lubricants, emulsifiers (biosurfactants), and viscosity agents (polysaccharides)). 

Willumsen and Karlson [125] screened 57 PAH-degrading bacteria isolated from PAH-contaminated soil for the production of biosurfactant compounds. The majority of the strains isolated on phenanthrene, pyrene, and fluoranthene were better emulsifiers than surface-tension reducers, and the stability of the... 

Microbially produced biosurfactants can also have important effects on increasing bioavailability and biodegradation (Zhang Miller, 1992). A new PCB-degrading strain was recently isolated and found to produce a bio-emulsifier (Rothmel et al., 1993). Experiments show that the bio-emulsifier stimulates the extent of PCB degradation well beyond the levels seen before with other Type strains of its class, and that the bio-emulsifier can stimulate the extent of PCB biodegradation of added co-cultures as well. 

All tested media produced a biosurfactant capable of emulsifying kerosene. However, except when EDTA was added alone (medium 4), the E24 values were satisfactory in comparison with those related to other emulsifiers produced by different microorganisms (30). 

Figure 5 shows some data referring to the ability of biosurfactant to emulsify kerosene produced by B. subtilis ATCC 6633 at the different substrate concentrations tested (5, 10, 20, and 40 g/L). Besides a decrease in surface tension, stabilization of hydrocarbon/water is frequently used as an indicator of surface activity. Note, however, that the quantity of biosurfactant produced should not be related to the E24 because that is an intrinsic property of the molecule. A similar behavior of the emulsifying activity in relation to the carbon source concentration and to the incubation period has been observed. The diverse initial concentrations of commercial sugar studied favor the formation of a surface-active compound, with an emulsifying activity >50% in a 48-h process. The maximum values for emulsion activity of 57.9 and 56.9% were determined for 10 and 20 g/L of substrate, respectively. It should be emphasized that there was a reduction in the E24 after a 96-h period of incubation. Carvalho et al. (36) reported similar results for cell-free fermented broth by Bacillus sp. emulsified in kerosene. 

Phospholipase D. An improved biosurfactant and emulsifier is made from lecithin by phospholipase D. The enzyme transphosphatidylates lecithin, converting most of the phosphatidylcholine and phophatidyl-ethanolamine to phosphatidylglycerol (49). 

Many organisms growing on hydrocarbons are able to produce substances that lower the interfacial tension of the growth medium, and may serve to emulsify oil in water (30, 38-41). Such biosurfactant production is believed to facilitate microbial uptake of hydrocarbon by increasing the substrate surface area via emulsification. Thus, it permits greater contact between hydrocarbon and bacteria and enhances the substrate dissolution rate. Alternatively, biosurfactant production may increase the solubility of the hydrocarbons, which are utilized only in solution. 

Bognolo G (1999). Biosurfactants as emulsifying agents for hydrocarbons. Colloids and Surfaces A—Physicochemical and Engineering Aspects 152(l-2) 41-52. 

Bile salts are biosurfactants naturally formed by cholesterol degradation in the liver. Bile acids are stored in the gall-bladder. After derivation with glycine or tauric acid, the sodium salts of the derivatives are essential in the digestion process to emulsify food triglycerides. The pancreatic lipase enzyme can only split emulsified fatty globules. 

Southam et al. [54] studied the effect of biosurfactants on the biodegradation of waste hydrocarbons. To degrade hydrocarbons, bacteria must adsorb onto the surfactant-oil interface of 25-50 nm in thickness. Approximately 1% of all the biosurfactant was needed to emulsify the oil. This type of studying with a transmission electron microscope showed that the microorganisms were able to uptake nanometre-sized oil droplets during growth. More of this type of research is required to determine the mechanism of hydrocarbon metabolism and biosurfactant applications. 

In contrary to the other surface active molecules, polymeric biosurfactants are high-molecular weight compounds and generally exhibit high emulsifying activity. Among current polymeric biosurfactants, a more potent one is emulsan. 

Bacillus subtilis produces lipopeptide biosurfactant called surfactin which has excellent surface activity. Unlike other biosurfactants, surfactin is highly hydrophilic and forms transparent gel which can be exploited in skin care formulation. Emul-san, a high-molecular weight biosurfactant produced by Acinetobacter calcoaceticus, exhibits high emulsifying activity. Emulsan can be used in soaps and shampoos... 

Certain bacteria and yeast produce extracellular biosurfactants that emulsify water into the fuel above the interface. The bacteria and yeast can invade the fuel phase in the water droplets (Figure 3) dispersed in the oil emulsion (Smith, 1991). 

Figure 3 Microorganisms can invade the fuel phase in a water droplet, emulsified in the fuel by biosurfactants produced by microorganisms. (Graphic courtesy of the Rohm and Haas Company, Philadelphia, Pennsylvania, U.S., Copyright the Rohm and Haas Company.)...

The essential literature data on the influenee of native mierobial biosurfactants on the surface tension of water are summarized in Table 4, and those on the emulsifying activity in Table 5. Interesting biologjeal activities are presented in Table 6. 

De Acevedo GT, Mclnerney MJ (1996) Emulsifying activity in thermophilic and extremely thermophilic microorganisms. J Ind Microbiol 16 17-22 Desai J, Banat I (1997) Microbial production of surfactants and their commercial potential. Microbiol Mol Biol Rev 61 47-48 Deziel E, Paquette G, Villemur R, Lepine F, Bisaillon JG (1996) Biosurfactant production by a soil Pseudomonas strain growing on polycyclic aromatic hydrocarbons. Appl Environ Microbiol 62(6) 1908-1912 Espuny MJ, Egido S, Rodon 1, Manresa A, Mercade ME (1996) Nutritional requirements of a biosurfactant producing strain Rhodococcus s p 51 T7. Biotechnol Lett 18 521-526... 

Luttinger A, Hahn J, Dubnau D (1996) Polynucleotide phosphoryiase is necessary for competence development in BaciUus subtilis. Mol Microbiol 19 343-356 MacDonald CR, Cooper DG, Zajic JE (1981) Surfece-active lipids from Nocardia erythropolis grown on hydrocarbons. Appl Environ Microbiol 41 117-123 Makkar RS, Cameotra SS (1997) Biosurfactant production by a thermophilic BaciUus subtilis strain. J Ind Microbiol Biotechnol 18(1) 37—42 Maneerat S, Bamba T, Harada K, Kobayashi A, Yamada H, Kawai F (2006) A novel crude oil emulsifier excreted in the culture supernatant of a marine bacterium, Myroidessp. strain SMI. Appl Microbiol Biotechnol 70 254-259 Marahiel MA (1997) Protein templates for the biosynthesis of peptide antibiotics. Chem Biol 4 4561-4567... 

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