Studies On Production,Physicochemical Properties And Antimicrobial Activity Research Of Lipopeptide

Biosurfacant have several outstanding advantages, such as higher biodegradabil- ity and no recontamination; lower toxicity; better environmental compatibility; higher foaming; higher selectivity and specific activity at extreme temperatures, pH, and salinity; and the ability to be synthesized from renewable feed stocks and so on. New structural types of biosurfactant can be produced and, thus, they expand the range of available surfactants. Compared with chemical surfactant, biosurfactant has obtained international attention because of its environment friendly and broad application potential. Therefore, the works of exploitation of bio-surfactant microorganism resource, improving their yield in fermentation solution, and studying of surfactant quantifying have extensive biological and economic significance.This article does comprehensive research about follow aspects: bacteria of prod- ucing biosurfactant could be isolated; high productivity bacteria was obtained through mutation breeding by ultraviolet; the morphological structure identification; the optim ization conditions for shaking flask fermentation of the strain; bacteria identification; the physicochemical properties, extraction and purification, component analysis of the production. These build theory basic for industrial produce and application.(1) microorganism L-104-1 which capable of high producing biosurfactant could be isolated through surface tension,diameter of ejecting oil and emulsification ability. The mutation breeding LY was obtained by ultraviolet, and it is excel original bacteria on all guideline. When used glucose as carbon source, the surface tension is 30.4mN/m, the emulsification in paraffin-water is 84.5%, the dimeter of ejecting oil in cetane-water is 11.2cm, and have a stabilization character the offspring. It showed that ultraviolet could lead to mutation and the result of mutation could be descendible. By suing VITEK2 systems, Biologe systems and conventional methods for bacteria identification, strain LY was identified as Bacillus Subtilis. The main effective composition was excreted outside to the cell, and was called outside-production. The composition that leads to lower surface tension was Lipopeptide.(2) Bioactive substance called biosurfactant was obtained from extracts of fermentati- on supernatant of the strain LY. We conducted the preliminary study on the physicochemical properties of the biosurfactant and the stability test. This biosurfactant is a kind of Lipopeptide. The critical micelle concentration of the product is about 30 mg/L. It possesses a high emulsifying activity to hydrophobic organic substance, such as liquid paraffin. The emulsification on water-oil still up to 80% after 10 days; The biosurfactant can keep its surface activity in high-salinity solution like 15% and in a wide pH range of 2-12. It also has more endurable to high temperature. When was disposed at 120℃it can still keep lower surface tension.(3) The optimization of the fermentation process of the Bacillus Subtilis LY strain laid a solid foundation for the manufactory production. The optimization experiment targeted at the principal components and cultivation condition was: carbon source as sucrose 60g/L, nitrogen source as (NH4)2SO4 and the C/N is 13/1, original pH 7.0, NaCl 1%, inoculant 4%, rotate speed 160r/min. With the combination of the optimized media and fermentation condition, the metabolism parameters of the fermentation process were assessed. The rule of change was identified: the end point of the fermentation period is 72h, when the quantity of strain improved 1.205 times compared with original condition. The producing level of the biosurfactant reached 211.2mg/L, was 1.253 times than before.(4) Did inhibition bacteria experience to the lipopetide which was distilled from LY,the results indicated that this lipopetide is found to significantly inhibit the growth of E scherichia coli, Staphylococcus aureaus, Pseudomonas aeruginosa and Proteus vulgaris, especially to Staphylococcus aureaus and Pseudomonas aeruginosa. When the concentration was diluted to 0.005g/L, they still had a good inhibiton effect. The antimicrobial activity is very stable to temperature, could edure to high and low temperature. It is more stabilization in nature and alkalescence condition and in acidity surroundings the antimicrobial activity is reduce. If add the lipopetide biosrufactant into the culture when it has a lower bacteria concentration, the more lipopetide addition the more markedness of the inhibition effect. While if add the lipopetide biosrufactant into the culture when it has a higher bacteria concentration, the inhibiton effect become weak and the time of sterilization delay. Pilot study on the mechanism of lipopetide antiblastic the bacterium shows that adding lipopetide could augment the cell membrane's andpenetrate and lead to the microbe die.