Biosurfactant production by Mucor circinelloides: Environmental applications and surface‐active properties

Biosurfactants are structurally a diverse group of surface‐active molecules widely used for various purposes in industry. In this study, among 120 fungal isolates, M‐06 was selected as a superior biosurfactant producer, based on different standard methods, and was identified as Mucor circinelloides on the basis of its nucleotide sequence of the internal transcribed spacer (ITS) gene. M. circinelloides reduced the surface tension to 26 mN/m and its EI₂₄ index was determined to be 66.6%. The produced biosurfactant exhibited a high degree of stability at a high temperature (121°C), salinity (40 g/L), and acidic pH (2–8). The fermentation broth's ability to recover oil from contaminated sand was 2 and 1.8 times higher than those of water and Tween 80, respectively. The ability of biosurfactant to emulsify crude oil in the sea and fresh water was 64.9 and 48% respectively. This strain could remove 87.6% of crude oil in the Minimal Salt Medium (MSM) crude oil as the sole carbon source. The results from a primary chemical characterization of crude biosurfactant suggest that it is of a glycolipid nature. The strain and its biosurfactant could be used as a potent candidate in bioremediation of oil‐contaminated water, soil, and for oil recovery processes.     

The application of a high throughput analysis method for the screening of potential biosurfactants from natural sources

The presence of biosurfactants in growth media can be evaluated by a variety of methods, none of which are suitable for high throughput studies. The method described here is based on the effect of meniscus shape on the image of a grid viewed through the wells of a 96-well plate. The efficacy of the method was demonstrated by the selection of a bacterium (producing a biosurfactant able to reduce the surface tension of pure water from 72 to 28.75 mN m^− 1) from a culture collection isolated from aviation fuel-contaminated land. The assay was found to be more sensitive, rapid and easy to perform than other published methods. It does not need specialised equipment or chemicals and excludes the bias which results from the surfactant properties of medium used for bacterial growth.     

Isolation and characterization of biosurfactant production under extreme environmental conditions by alkali-halo-thermophilic bacteria from Saudi Arabia

Twenty three morphologically distinct microbial colonies were isolated from soil and sea water samples, which were collected from Jeddah region, Saudi Arabia for screening of the most potent biosurfactant strains. The isolated bacteria were selected by using different methods as drop collapse test, oil displacement test, blue agar test, blood hemolysis test, emulsification activity and surface tension. The results showed that the ability of Virgibacillus salarius to grow and reduce surface tension under a wide range of pH, salinities and temperatures gives bacteria isolate an advantage in many applications such as pharmaceutical, cosmetics, food industries and bioremediation in marine environment. The biosurfactant production by V. salarius decreased surface tension and emulsifying activity (30 mN/m and 80%, respectively). In addition to reducing the production cost of biosurfactants by tested several plant-derived oils such as jatropha oil, castor oils, jojoba oil, canola oil and cottonseed oil. In this respect the feasibility to reusing old frying oil of sunflower for production rhamnolipids and sophorolipids, their use that lead to solve many ecological and industrial problems.     

Effect of emulsified feeding of oily substrate via submerged ceramic membranes on surfactant production in <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> fermentation

Aqueous two-phase systems often face mass transfer limitations due to very poor miscibility of the fluids, and to enhance the homogeneity (or emulsification) in the reaction volume, high energy inputs are required which result in high shear forces in the culture medium. For the purposes of emulsification, microporous systems have advantages over other conventional methods due to mild operating conditions and narrow droplet-size distribution. In this study, emulsification within the culture volume was achieved by feeding the oily substrate (dispersed phase) into the aqueous medium (dispersion phase) via ceramic membranes integrated in the bioreactor. The method was investigated for bioprocesses aimed at producing rhamnolipids and polyhydroxyalkanoates (PHA). Better homogenization of the mixed volume and hence improved consumption of oily substrate was successful. Surfactants are produced by various bacterial cultures, especially Pseudomonas aeruginosa species, when oil is present as the only carbon source. Are surfactants produced only as a result of bacteria feeding on the oily substrate, or as a requirement to feed on the oily substrate, owing to their surface-active characteristics? This paper also intends to draw some conclusions in this respect.     

Modifications and applications of the <Emphasis Type="Italic">Acinetobacter venetianus</Emphasis> RAG-1 exopolysaccharide,the emulsan complex and its components

Since its discovery in the late 1970s, emulsan has been the subject of significant interest for fundamental biosynthesis and structure–function relationships as well as for its potential industrial applications. These studies initially examined the emulsification properties of the compound, while more recent efforts have focused on potential biomedical applications. As a result of this change of focus, it became necessary to more completely characterize the structure of the emulsan molecule and to develop a more reproducible purification process. We review previous studies with emulsan and explain how prior notions were recently shown to be incorrect through the development of a new purification process. More recent genetic modification of the relevant operon is also reviewed. Finally, the potential applications for the new purified polymer will be discussed.     

伤寒Vi多糖疫苗大规模生产中的工艺改进

对伤寒Ｖｉ多糖疫苗大规模生产进行了三项工艺改进：１．将液体菌种由静止期接种大罐改为对数生长期接种大罐,大罐培养时间可缩短３－４小时。２．２％（Ｖ／Ｖ）甲醛溶液杀菌时间由５℃６小时改为２０－２５℃２小时,能保证杀菌完全。３．用冷酚精制Ｖｉ多糖由常规法改为乳化法,可减少精制次数及冷酚用量,提高多糖收率     

The reduction of wax precipitation in waxy crude oils by <Emphasis Type="Italic">Pseudomonas</Emphasis> species

Crude oil with different concentrations was subjected to Pseudomonas species at 37 degrees C and various incubation periods. The results showed that Pseudomonas species grew faster at 1% (v/v) concentration of crude oil and exhibited high biodegradation ability within 1 week. On measuring the emulsification activity and emulsion stability during different stages of growth, in various immiscible hydrocarbons, it appeared that the species was able to produce a stable emulsion with a maximum at the end of stationary phase of growth. The gas chromatography analysis of the saturated hydrocarbons of crude oil showed that, an increase in concentration of iso-alkanes in the range of C15-C20, and a bioconversion of heavy iso-alkanes in the range of C21-C22+. Chemical analysis of crude oil by liquid chromatographic technique before and after growth showed that, the saturated alkanes were more degradable than aromatic and asphaltenic compounds. Treatment by Pseudomonas species may possibly be an effective method for the biodegradation of heavy paraffinic hydrocarbon leading to an enhancement in crude oil properties.     

Structural characterization and surface activity of hydrophobically functionalized extracted pectins

The technological properties of pectins are generally influenced by their chemical modification. Thus, amidated pectins are important derivatives with good emulsifying properties at low concentrations. The present article focuses on the comparative study of physicochemical properties of three modified pectin derivatives. Various amphiphilic derivatives in which pectin is associated with hydrophobic amines chains were prepared. The reaction was carried out in heterogeneous medium in methanol at 20 °C for 7 days and with 0.5 pectin/alkylamine mass ratio. The degrees of amidation (DA) of the derivatives were calculated based on the results of FTIR spectroscopy. The surface-active properties of the modified pectins were determined by surface tension (air/water) and interfacial tension (oil/water) measurements. The aminolysis of pectins appears to be an interesting way to produce pectin derivatives with new properties able to stabilize oil-in-water emulsions.     

Kocuria marina BS-15 a biosurfactant producing halophilic bacteria isolated from solar salt works in India

Biosurfactant screening was made among the eight halophilic bacterial genera isolated from Kovalam solar salt works in Kanyakumari of India. After initial screening, Kocuria sp. (Km), Kurthia sp. (Ku) and Halococcus sp. (Hc) were found to have positive biosurfactant activity. Biosurfactant derived from Kocuria sp. emulsified more than 50% of the crude oil, coconut oil, sunflower oil, olive oil and kerosene when compared to the other strains. Further, Kocuria marina BS-15 derived biosurfactant was purified and characterized by TLC, FTIR and GC–MS analysis. The TLC analysis revealed that, the purified biosurfactants belong to the lipopeptide group. The IR spectrum results revealed that functional groups are R₂CNN, alkenes and N–H. The GC–MS analysis confirmed the compound as Nonanoic acid and Cyclopropane with the retention time of 12.78 and 24.65, respectively.     

Physiological aspects. Part 1 in a series of papers devoted to surfactants in microbiology and biotechnology

Surfactants, both chemical and biological, are amphiphilic compounds which can reduce surface and interfacial tensions by accumulating at the interface of immiscible fluids and increase the solubility, mobility, bioavailability and subsequent biodegradation of hydrophobic or insoluble organic compounds. Investigations on their impacts on microbial activity have generally been limited in scope to the most common and best characterized surfactants. Recently a number of new biosurfactants have been described and accelerated advances in molecular and cellular biology are expected to expand our insights into the diversity of structures and applications of biosurfactants. Biosurfactants play an essential natural role in the swarming motility of microorganisms and participate in cellular physiological processes of signaling and differentiation as well as in biofilm formation. Biosurfactants also exhibit natural physiological roles in increasing bioavailability of hydrophobic molecules and can complex with heavy metals, and some also possess antimicrobial activity. Chemical- and indeed bio-surfactants may also be added exogenously to microbial systems to influence behaviour and/or activity, mimicking the latter effects of biosurfactants. They have been exploited in this way, for example as antimicrobial agents in disease control and to improve degradation of chemical contaminants. Chemical surfactants can interact with microbial proteins and can be manipulated to modify enzyme conformation in a manner that alters enzyme activity, stability and/or specificity. Both chemical- and bio-surfactants are potentially toxic to specific microbes and may be exploited as antimicrobial agents against plant, animal and human microbial pathogens. Because of the widespread use of chemical surfactants, their potential impacts on microbial communities in the environment are receiving considerable attention.