Mg-Fe Layered Double Hydroxides Enhance Surfactin Production in Bacterial Cells

Pei-Hsin Chang,Tzong-Yuan Juang,Si-Yu Li,Yung-Chuan Liu

doi:10.3390/cryst9070355

Pei-Hsin Chang, Tzong-Yuan Juang + Show 2 more

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https://doi.org/10.3390/cryst9070355

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Abstract

In this study, four additives—montmorillonite, activated carbon, and the layered double hydroxides (LDHs), Mg2Fe–LDH and Mg2Al–LDH—were tested for their ability to promote surfactin production in a Bacillus subtilis ATCC 21332 culture. Among these tested materials, the addition of 4 g/L of the Mg-Fe LDH, which featured an Mg/Fe molar ratio of 2:1, produced the highest surfactin yield of 5280 mg/L. During the time course of B. subtilis cultivation with the added LDH, two phases of cell growth were evident: Growth and decay. In the growth phase, the cells grew slowly and secreted a high amount of surfactin; in the decay phase, the cells degraded rapidly. The production in the presence of the Mg2Fe–LDH had three characteristics: (i) High surfactin production at low biomass, indicating a high specific surfactin yield of 3.19 g/g DCW; (ii) rapid surfactin production within 24 h, inferring remarkably high productivity (4660 mg/L/d); and (iii) a lower carbon source flux to biomass, suggesting an efficient carbon flux to surfactin, giving a high carbon yield of 52.8%. The addition of Mg2Fe–LDH is an effective means of enhancing surfactin production, with many potential applications and future industrial scale-up.

Highlights

Biosurfactants are amphipathic molecules produced by microorganisms [1,2,3] with the capability of decreasing surface and interfacial tension [4]
The addition of Mg2 Al–layered double hydroxides (LDHs) LDH to a surfactin production fermentation system involving B. subtilis incubation revealed that surfactin could intercalate into the LDH layer gallery to form a surfactin–LDH complex; this phenomenon occurred with a significant increase in the production of surfactin [33]
We examined the effect of adding this iron salt LDH to B. subtilis cultivation to study whether it, too, would promote surfactin production

Summary

Introduction

Biosurfactants are amphipathic molecules produced by microorganisms [1,2,3] with the capability of decreasing surface and interfacial tension [4] Depending on their chemical composition and their producing organism, biosurfactants can possess high biodegradability, low toxicity, ecological acceptability, and high efficiency. Bacillus spp., bacterial strains of complicated physiological diversity, can be used to produce many bioactive peptides with potential biotechnological and biopharmaceutical applications Among these peptides, the lipopeptides that feature an alkyl group and a circular peptide group are the most popular biosurfactants [7]; these materials include surfactins [8,9,10], iturins [11,12], and fengycins [13]. Surfactin can lower the surface tension of water to 27 mN/m even when its concentration is as low as 0.005% [7,10,15,16], suggesting its great potential applicability

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