Optimization of cultivation conditions for biosurfactant production by Bacillus mojavensis P1709, Pseudomonas putida PP021, and Pseudomonas fluorescens PCS-20 strains

Kazan (Volga Region) Federal University, 18, Kremlevskaya, 42008, Kazan, Russian Federation

^* Corresponding author: drgor@mail.ru

Abstract

Biosurfactants, being a promising group of compounds for agriculture, oil production and environmental protection, need further study. Including ways of their production by cultivation of microorganisms obtained from various sources. In this study, the effect of nutrient medium composition on the production of biosurfactants by Bacillus mojavensis P1709, Pseudomonas putida PP021 and Pseudomonas fluorescens PCS-20 strains was investigated. The emulsification index (E24) and surface tension (ST) of culture supernatants were determined to evaluate the surfactant properties of the biosurfactants. BH medium with glucose was found to be optimal for B. mojavensis strain P1709, providing an E24 of 61% and ST of 28.3 mN m^-1. For P. putida strain PP021 and P. fluorescens strain PCS-20, the best results were obtained on glycerol-nitrate medium with E24 85% and 80%, and ST 27.5 mN m^-1 and 29.4 mN m^-1, respectively. Medium with hexane as the sole carbon source showed lower efficiency. Further cultivation of the selected strains on optimal media for 72 hours revealed that minimum ST values were reached by 36 hours for B. mojavensis P1709 (23.96 mN m^-1) and P. fluorescens PCS-20 (24.4 mN m^-1), and by 72 hours (27.5 mN m^-1) for P. putida PP021. Despite reaching the plateau of cell growth, the decrease in ST continued, which may be due to changes in biosurfactant composition.