الفهرس 
Definition of bio-surfactantsOnly 14 pages are availabe for public view
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Abstract
At the last few decades, Microbial bio-surfactants received great attention due to their low toxicity and biodegradability. As synthetic surfactants showed higher toxicity and low biodegradability.
Bio-surfactants have amphiphilic nature, where they can reduce the surface tension and interfacial tension by accumulating at the interface between two immiscible liquids.
Diesel oil is considered one of the environmental pollutants where it is wide spread in all the world. where at automobiles the diesel oil is spread on the soil, whichnegatively affect on the growth of microorganisms as not all the microorganisms are able to degrade the diesel oil. As this oil has complicated chemical structure.
Biodegradation of diesel oil requires production of such compounds that able to make it miscible with water in order to facilitate its bioavailability and enhance microbial uptake.
Actinomycetes are considered one of the most important microorganisms that are able to produce several types of secondary metabolites;actinomycetes have good ability in bio-surfactants production.
Microbial surfactants have many properties make them compatible with many fields such as; soil bioremediation, food industries, pharmaceutical industries and textile industries. to the ability of bio-surfactants to make emulsification of the oils in water compared with other synthetic surfactants, also bio-surfactants has many advantage as they are low toxic, biodegradable,biocompatibility and digestibility, Effectiveness, at extreme temperatures, pH and salinity, and low irritancy and compatibility with human skin.
Twenty five actinomycetes isolates were isolated from different soils in El-Menofia governorate.
Screening for bio-surfactants producing actinomycetes isolates were done firstly by testing biodegradation of diesel oil on agar medium where the isolates that able to produce bio-surfactants are able to grow on such growth medium.
Another specific nature for bio-surfactants producing isolates, is lipase production as the isolates, which able to produce lipase enzyme mainly can produce bio-surfactants so that, the isolates were applied to tributyrene medium where the clear zones resulted showed the hyper bio-surfactants producing isolates.
Hemolytic activities were studied on blood agar medium where, clear zone appeared on the blood agar plates mean that the organisms were able to produce lipase enzyme, which were able to make lysis for the erythrocytes on blood.
Optimization for microbial bio-surfactant production was carried out by studying the optimum growth conditions for the bio-surfactants production. Incubation period were found to be important factor on the bio-surfactants production as 7 days incubation period were found to be the optimum period for bio-surfactants production.
Volume of inoculum also affectsbio-surfactants production also the higher increasing was found to have negative effect on bio-surfactants production. 2% inoculum volume was found to be the ideal volume that enhances production of bio-surfactants.
The ratio of diesel oil as the soul carbon source in the growth medium was found to be critical factor. Percent of the diesel oil affect on bio-surfactant production. Although, isolates were able to grow on different concentrations of diesel oil, bio-surfactants production were found to be affected by different concentrations of diesel oil. 1.5% concentration of diesel oil was found to be the ideal concentration enhances bio-surfactant production.
Nitrogen is the second macro element affect on the microbial growth. Production of bio-surfactant affected with the type of nitrogen source as in this case study (potassium nitrate, ammonium chloride,ammonium nitrate, and urea) were used as nitrogen sources, where it was found that urea and ammonium nitratestimulate the production of bio-surfactants.
Nitrogen source ratio plays key role in bio-surfactant production where, when nitrogen percent increased on the growth medium the bio-surfactant production increased. Nitrogen percent has remarkable effect on the bio-surfactant production, as nitrogen is the main component on enzymes and amino acids which mainly enhance production of secondary metabolites and contribute on its chemical composition.Physical parameters are important in microbial growth, that affect on the growth of microorganisms and their manner on production of bio-surfactants.
Microbial growth is sensitive to temperature where the temperature affect on the microorganisms growth and physiological activities inside the microbial cells. In the case study the isolates were applied to grow on temperature range form (20 °C up to 60 °C). The optimum temperature for bio-surfactants production was found to be 30 °C.
Bio-surfactantsproduction was affected by pH range, where in acidic pH the bio-surfactant production were very low as well as alkaline pH.The optimum pH for bio-surfactant production was found to be in PH 7.0.
The hyperbio-surfactant producing actinomycetes isolate were submitted to the phenotypic characterization through morphological, physiological and biochemical tests according to Bergey’s manual for systematic bacteriology, Phenotypic characteristics such as Gram’s staining, growth on different growth medium such as starch nitrate medium, yeast extract-malt extractmedium, oat meal agar medium,Bennett’s agar medium and glycerol-asparagine agar medium, cell wall phospholipids also were tested, also enzymatic activities such as catalase, urease,…etc., were studied by adopting standard procedures. Also, pH and temperature on growth was tested.
The actinomycetes isolate also submitted to genotypic characterization through 16S rRNA gene technique, where it was found to be related to Streptomyces viridochromogenes.