Evaluation of different nitrogen sources in production of surfactant by Pseudomonas putida KT-۲۴۴۰

Biosurfactants are used to increase the availability of nutrients in plant nutrition and bioremediation of contaminated soils. These compounds are biodegradable and can be produced from inexpensive renewable sources. In this study, aiming to find the optimal conditions of surfactant synthesis from Pseudomonas putida KT-۲۴۴۰ in using sugarcane molasses as carbon source, the effect of different nitrogen sources (urea, sodium nitrate, ammonium chloride and ammonium nitrate), different carbon to nitrogen ratio (۱:۱۰, ۱:۲۰, ۱:۳۰ and ۱:۴۰) and incubation time (۱, ۴, ۶ and ۸ days) were investigated in separate experiments. The optimal treatment of each experiment was used in the next step .For this purpose, the pH of the culture medium, surface tension and dry weight of biosurfactant were measured. Among nitrogen sources, ammonium chloride showed the least surface tension at ۵۵.۹۳ mN.m-۱ compared to the control (۷۴.۵۵ mN.m-۱). While the highest dry weight of biosurfactant was obtained in the application of sodium nitrate (۴.۵ g.L-۱). The results showed that compared to the initial pH of the culture medium (۷), the final pH of the solution decreased in application of ammonium chloride and increased in the other sources. By measuring the weight of biosurfactant at the pHs adjusted (۷ and ۲), it was found that the pH of the final solution affects the deposition of the biosurfactant in acetone method. In the application of sugarcane molasses and sodium nitrate, the lowest surface tension was measured in C:N ratio of ۱:۱۰ (۳۹.۹۲ mN.m-۱). Also, in this ratio, the highest dry weight of biosurfactant was obtained at neutral pH (۲.۷۳ g.L-۱). After the sixth day, time did not have a significant effect on the measured parameters in this treatment. The biosurfactant produced was investigated using Fourier-transform infrared )FTIR(spectroscopy. use of different nitrogen sources showed a significant effect on biosurfactant production, also the use of sugarcane molasses as an available and inexpensive raw material in the production of biosurfactants is recommended.

کلیدواژه ها:

biosurfactant ، surface tention ، sugarcane molasses