Sustainable biosurfactant produced by Serratia marcescens UCP 1549 and its suitability for agricultural and marine bioremediation applications

Abstract

Background: Biosurfactants are surface-active agents produced by microorganisms that have higher efficiency and stability, lower toxicity and higher biocompatibility and biodegradability than chemical surfactants. Despite its properties and potential application in a wide range of environmental and industrial processes, biosurfactants are still not cost-competitive when compared to their synthetic counterparts. Cost effective technologies and renewable raw substrates as agro-industrial and regional waste from northeast of Brazil as cassava flour wastewater, supplemented with lactose and corn oil are mainly the chemically media for growing microorganism and in turn the production of the biosurfactant of quality. This study aimed to obtained biosurfactant by Serratia marcescens UCP 1549 containing cassava flour wastewater (CWW), by application of a full-factorial design, as sustainable practices in puts the production process in promising formulation medium. The characterization of the biomolecule was carried out, as well as the determination of its stability and toxicity for cabbage seeds. In addition, its ability to stimulate seed germination for agriculture application and oil spill bioremediation were investigated.

Results: Serratia marcescens showed higher reduction of surface tension (25.92 mN/m) in the new medium containing 0.2% lactose, 6% cassava flour wastewater and 5% corn waste oil, after 72 h of fermentation at 28 °C and 150 rpm. The substrate cassava flour wastewater showed a promising source of nutrients for biosurfactant production. The isolate biosurfactant exhibited a CMC of 1.5% (w/v) and showed an anionic and polymeric structure, confirmed by infrared spectra. The biomolecule demonstrated high stability under different temperatures, salinity and pH values and non-toxicity against to cabbage seeds. Thus, exploring biosurfactant their potential role in seeds germinations and the promotion and agricultural applications was investigated. In addition, the effectiveness of biosurfactant for removal burned motor oil adsorbed in sand was verified.

Conclusions: The use of medium containing CWW not only reduces the cost of process of biosurfactant production, but also the environmental pollution due to the inappropriate disposal of this residue. This fact, added to the high stability and non-toxicity of the biosurfactant produced by S. marcescens UCP 1549, confirms its high environmental compatibility, make it a sustainable biocompound that can be replace chemical surfactants in diverse industries. In addition, the effectiveness of biosurfactant for stimulate seed germination and removing burned motor oil from sand, suggests its suitability for agriculture and bioremediation applications.

Keywords: Biosurfactant; Cassava flour wastewater; Oil removing; Seed germination; Serratia marcescens.

Fig. 1

Observed values versus predicted values by model for the answer surface tension

Fig. 2

Cubic plot of the surface tension values estimated from the full-factorial design of Table 2

Fig. 3

Kinetic profiles of growth, surface tension and pH of Serratia marcescens UCP 1549. The strain was grown in medium containing 0.2% lactose, 6% CWW and 5% CO during 120 h at 150 rpm and 28 °C

Fig. 4

Stability of surface tension of biosurfactant produced by Serratia marcescens UCP 1549. Influence of pH (a), temperature (b) and sodium chloride concentrations (c) on surface tension of biosurfactant produced by S. marcescens UCP 1549 after 72 h of fermentation

Fig. 5

Critical micelle concentration of the biosurfactant produced by Serratia marcescens UCP 1549. Surface tension versus concentration of isolated biosurfactant produced by S. marcescens UCP 1549 after 72 h of fermentation

Fig. 6

Fourier transform-infrared (FT-IR) spectra of the biosurfactant produced by Serratia marcescens UCP 1549

Fig. 7

Phytotoxicity of biosurfactant produced by Serratia marcescens UCP 1549 on seeds of cabbage (Brassica oleracea)

Fig. 8

Application of biosurfactant produced by Serratia marcescens UCP 1549 in removal of burned motor oil from contaminated sand. Beach sand artificially contaminated with burned motor oil: without treatment (a) and after treatment with distilled water (b) and biosurfactant produced by S. marcescens UCP 1549 (c)