Effect of Fe nanoparticle on growth and glycolipid biosurfactant production under solid state culture by marine Nocardiopsis sp. MSA13A

Abstract

Background: Iron is an essential element in several pathways of microbial metabolism, and therefore low iron toxicity is expected on the usage of Fe nanoparticles (NPs). This study aims to determine the effect of Fe NPs on biosurfactant production by marine actinobacterium Nocardiopsis sp. MSA13A under solid state culture. Foam method was used in the production of Fe NPs which were long and fiber shaped in nature.

Results: The SEM observation showed non toxic nature of Fe NPs as no change in the morphology of the filamentous structure of Nocardiopsis MSA13A. The production of biosurfactant by Nocardiopsis MSA13A under solid state culture supplemented with Fe NPs increased to 80% over control. The biosurfactant produced by Nocardiopsis MSA13A was characterized as glycolipid derivative which effectively disrupted the pre-formed biofilm of Vibrio pathogen.

Conclusion: The use of metal NPs as supplement would reduce the impact of non-metallic ions of the metal salts in a fermentation process. This would ultimately useful to achieve greener production process for biosurfactants. The present results are first report on the optimization of biosurfactant production under SSC using Fe NPs.

Figure 1

SEM observation of (A) fiber-shaped Fe nanoparticles (diameter nano size) synthesized using foam method (B) Nocardiopsis morphology after 4 h interaction with 10 mg/L Fe NPs (C) EDS analysis of freshly synthesized Fe NPs showing high percentage of iron element.

Figure 2

Effect of Fe NPs on the growth rate and biosurfactant production by Nocardiopsis MSA13A. Lag period was fall on 0 to 2 d which is not shown in the Figure. The growth rate was presented in terms of percent increase over the control. Growth rate was derived from colony plate count and OD values. 10 mg/L Fe NPs induced growth rate of Nocardiopsis MSA13A to the maximum of 67% over control. The same Fe NPs concentration increased to 80% biosurfactant production over control.

Figure 3

Effect of carbon and nitrogen sources on biosurfactant production. A) Effect of increasing concentration of optimized carbon source, glucose on the production of biosurfactant B) Effect of increasing concentration of optimized nitrogen source, yeast extract on the production of biosurfactant by Nocardiopsis MSA13A.

Figure 4

Statistical optimization of biosurfactant production. A. Contour plot of the interaction between the glucose (carbon source) and yeast extract (nitrogen source) on the production of biosurfactant in SSC by Nocardiopsis MSA13A. B. Contour plot of the interaction between the Fe NPs and inoculum size on the production of biosurfactant.

Figure 5

Purification and chemical characterization of biosurfactant. A) TLC results of carbohydrate and lipid fractions of biosurfactant. B) MS spectra of lipid moiety of glycolipid biosurfactant showing non-polar hydrocarbon chain (hexacosanoic acid, propyl ester). C) MS spectra of sugar moiety of glycolipid biosurfactant showing methyl-4- O-methyl-beta-D-xylopyranoside.

Figure 6

Effect of biosurfactant on biofilm disruption. (A) The cells were tightly bound by exopolysaccharies, shows biofilm (B) The effect of biosurfactant on the pre-formed (24 h) biofilm. The biofilm nature was disrupted and few microcolonies of Vibrio alginolyticus was remaining after the disruption of preformed biofilm by biosurfactant.