Effects of Au/Fe and Fe nanoparticles on Serratia bacterial growth and production of biosurfactant

Available strategies for improving the biosynthesis of surfactin: a review

Surfactin is an excellent biosurfactant with a wide range of application prospects in many industrial fields. However, its low productivity and high cost have largely limited its commercial applications. In this review, the pathways for surfactin synthesis in Bacillus strains are summarized and discussed. Further, the latest strategies for improving surfactin production, including: medium optimization, genome engineering methods (rational genetic engineering, genome reduction, and genome shuffling), heterologous synthesis, and the use of synthetic biology combined with metabolic engineering approaches to construct high-quality artificial cells for surfactin production using xylose, are described. Finally, the prospects for improving surfactin synthesis are discussed in detail.

Evaluation of SDS‐coated iron nanostructure on the gene expression of bio surfactant‐producing genes by Pseudomonas aeruginosa

Bio surfactants are natural surfactants that induce emulsification, displacement, increased solubility, and mobility of hydrophobic organic compounds. In this study, the gene expression of biosurfactant production genes by Pseudomonas aeruginosa in the presence of sodium dodecyl sulfate coated iron nanostructure (Fe/SDS) were evaluated. Emulsification Index and Surface Tension reduction test to check stability and emulsification the rhamnolipid were done. Purification was evaluated using thin layer chromatography (TLC) and expression of rhlA, mvfR, lasR, rhlR genes was determined using q‐PCR technique. Binding of nanoparticles to bio surfactants was confirmed by TEM. The best emulsification index, was by the sample that exposed to 1 mg/L Fe/SDS nanoparticles for 2 days. Rhamnolipid produced in the presence of nanoparticles had an acceptable ability to reduce surface tension. The Rf (retention factor) value obtained was 0.63 by chromatography. q‐PCR results showed that the expression of rhlA, mvfR, lasR, rhlR genes was significantly increased in Fe/SDS treated cells, which indicates the significant positive effect (P < 0.05) of nanoparticles on biosurfactant production of treated cells. While, SDS and Fe alone were not affected significantly (P > 0.05) on the expression of these genes. Our findings indicated the importance of nanoparticles in increasing the expression of genes involved in the bio surfactant production pathway of Pseudomonas aeruginosa.

Impact of biosurfactant and iron nanoparticles on biodegradation of polyaromatic hydrocarbons (PAHs)

Polycyclic aromatic hydrocarbons (PAHs) are hazardous toxic contaminants and considered as primary pollutants due to their persistent nature and most of them are carcinogenic and mutagenic. The key challenge in PAHs degradation is their hydrophobic nature, which makes them one of the most complex materials and inaccessible by a broad range of microorganisms. This bioavailability can be increased by using a biosurfactant. In the present study mixed PAHs were degraded using the biosurfactant producing bacterial strains. In addition, iron nanoparticles were synthesized and the impact of iron nanoparticles on the growth of the mixed bacterial strains (Pseudomonas stutzeri NA3 and Acinetobacter baumannii MN3) was optimized. The mixed PAHs (anthracene, pyrene, and benzo(a)pyrene) degradation was enhanced by addition of biosurfactant (produced by Bacillus subtilis A1) and iron nanoparticles, resulting in 85% of degradation efficiency. The addition of the biosurfactant increased the bioavailability of the PAHs in the aqueous environment, which might help bacterial cells for the initial settlement and development. The addition of iron nanoparticles increased both bacterial biomass and PAHs adsorption over their surface. These overall interactions assisted in the utilization of PAHs by the mixed bacterial consortia. This study illustrates that this integrated approach can be elaborated for the removal of the complex PAHs pollutants from soil and aqueous environments.

Antibacterial activity of γFe2 O3 /TiO2 nanoparticles on toxic cyanobacteria from a lake in Southern Illinois

Frequent outbreaks of harmful algal blooms (HABs) have brought adverse impacts on human health, economic viability, and recreational activities in many communities in the United States. Cyanobacteria (or blue-green algae) blooms are the most common type of HABs in surface water. Current bactericides for controlling the blooms are disadvantageous due to the recycling difficulty. In this study, an innovative magnetic nanomaterial-γFe₂ O₃ /TiO₂ nanoparticle-was used to inactivate toxic cyanobacteria species found in a lake in Southern Illinois that frequently experienced HABs. Cyanotoxin genes of mcy, nda, cyr, and sxt were used for targeting microcystin-, nodularin-, cylindrospermopsin-, and saxitoxin-producing cyanobacteria, respectively, by quantitative polymerase chain reaction (PCR) method. It was found that the concentration of chlorophyll a presents a strong correlation (R²  = 0.6024) with the gene copy obtained from 16S rRNA targeted for all cyanobacteria, but not with that from individual toxigenic cyanobacteria. The inactivation efficiencies of the nanomaterials under visible light were as high as 5-log and 1-log for cyanobacteria species containing mcyE/ndaF and sxtA genes, respectively, an improvement over the treatment under darkness. These nanomaterials can be recycled by their magnetic properties for reuse. Communities susceptible to HAB outbreaks are expected to benefit from the developed method for mitigating the blooms. PRACTITIONER POINTS: Lab-made γFe₂ O₃ /TiO₂ nanoparticles can be used to inactivate microcystin/nodularin- and saxitoxin-producing cyanobacteria species. qPCR method can be used for targeting toxic cyanobacteria; Chl a cannot be used as a standalone indicator for HABs. Better inactivation efficiency under visible light indicated possible application of the technology under sunlight for HAB mitigation from surface water.

The Impact of Nanoparticles on Innate Immune Activation by Live Bacteria

The innate immune system evolved to detect and react against potential dangers such as bacteria, viruses, and environmental particles. The advent of modern technology has exposed innate immune cells, such as monocytes, macrophages, and dendritic cells, to a relatively novel type of particulate matter, i.e., engineered nanoparticles. Nanoparticles are not inherently pathogenic, and yet cases have been described in which specific nanoparticle types can either induce innate/inflammatory responses or modulate the activity of activated innate cells. Many of these studies rely upon activation by agonists of toll-like receptors, such as lipopolysaccharide or peptidoglycan, instead of the more realistic stimulation by whole live organisms. In this review we examine and discuss the effects of nanoparticles on innate immune cells activated by live bacteria. We focus in particular on how nanoparticles may interfere with bacterial processes in the context of innate activation, and confine our scope to the effects due to particles themselves, rather than to molecules adsorbed on the particle surface. Finally, we examine the long-lasting consequences of coexposure to nanoparticles and bacteria, in terms of potential microbiome alterations and innate immune memory, and address nanoparticle-based vaccine strategies against bacterial infection.

Surfactin production in the bioreactor: Emphasis on magnetic nanoparticles application

Surfactin is one of the main lipopeptide biosurfactants produced by different species of Bacillus subtilis. This study aims to analyze the effect of starch-coated Fe0 and Fe3+ nanoparticles on the biomass and biosurfactant production of Bacillus subtilis. Out of 70 soil samples, 20 Bacillus were isolated and genome sequenced by biochemical methods and 16S rRNA gene. Quantitative and qualitative screening methods were used to isolate and detect biosurfactant production. For the aim of this study, 61 and 63 (Bacillus subtilis subsp. Inaquosorum) were selected. Then, hemolytic activity, biomass amount, surfactant production, and reduction of surface tension in Minimal Salt Medium containing Fe0 and Fe3+ nanoparticles were examined after 48, 72, and 96 h of culture. Strain 61 was the best bacterium and Fe3+ was the best nanoparticle. The results were compared with the results of non-nanoparticle bioreactor. The results showed the amount of biomass, surfactin, and surface tension decrease, 72 h after growth in 61 strain containing Fe3+ reached the highest values. Surfactin from strain 61 culture in the Fe3+nanoparticle bioreactor after 72 h of growth showed higher production than the same strain culture after 72 h without Fe3+, if continuing the research, this strain can be commercialized in the future.

Ectoine production in bioreactor by Halomonas elongata DSM2581: Using MWCNT and Fe-nanoparticle

Halomonas elongate produces ectoine to protect itselt from environmental stresses. In this research, important factors in the production of ectoine were optimized using statistical methods to achieve the best production efficiency in bioreactor. Screening important variables (ectoine, hydroxyectoine, l-aspartic acid, and glutamate) on H. elongate growth showed that ectoine and l-aspartic acid directly affect ectoine production. Two nanostructures, multiwalled carbon nanotube (MWCNT) and iron oxide nanoparticle (Fe₂ O₃ NPs), were used to increase the availability of substrate for the microorganism. The results showed that Fe₂ O₃ nanoparticles and MWCNT could have a negative or positive effect on bacterial growth and ectoine production depending on the concentration of nanoparticles. At optimized conditions, the amounts of bacterial growth and ectoine production in fermenter were 10.4 g/L and 14.25 g/L, respectively. Therefore, it could be concluded that nanoparticles improve bacterial growth and ectoine production at optimized concentrations.

Inorganic particulate matter modulates non-typeable Haemophilus influenzae growth: a link between chronic bacterial infection and geogenic particles

Australian Aboriginal populations have unacceptably high rates of bronchiectasis. This disease burden is associated with high rates of detection of pathogenic bacteria, particularly non-typeable Haemophilus influenzae (NTHi). While there is evidence to suggest that exposure to inorganic particulate matter (PM) is associated with worse respiratory infections, no studies have considered the direct effect of this PM on bacterial growth. Nine clinical isolates of pathogenic NTHi were used for this study. Isolates were exposed to two common iron oxides, haematite (Fe₂O₃) or magnetite (Fe₃O₄), or quartz (SiO₂), as the main constituents of environmental inorganic PM. NTHi isolates were exposed to PM with varying levels of heme to identify whether the response to PM was altered by iron availability. The maximal rate of growth and maximum supported growth were assessed. We observed that inorganic PM was able to modify the maximal growth of selected NTHi isolates. Magnetite and quartz were able to increase maximal growth, while haematite could both increase and suppress the maximal growth. However, these effects varied depending on iron availability and on the bacterial isolate. Our data suggest that inorganic PM may directly alter the growth of pathogenic NTHi. This observation may partly explain the link between exposure to high levels of crustal PM and chronic bacterial infection in Australian Aboriginals.

Biosurfactants, natural alternatives to synthetic surfactants: Physicochemical properties and applications

Biosurfactants comprise a wide array of amphiphilic molecules synthesized by plants, animals, and microbes. The synthesis route dictates their molecular characteristics, leading to broad structural diversity and ensuing functional properties. We focus here on low molecular weight (LMW) and high molecular weight (HMW) biosurfactants of microbial origin. These are environmentally safe and biodegradable, making them attractive candidates for applications spanning cosmetics to oil recovery. Biosurfactants spontaneously adsorb at various interfaces and self-assemble in aqueous solution, resulting in useful physicochemical properties such as decreased surface and interfacial tension, low critical micellization concentrations (CMCs), and ability to solubilize hydrophobic compounds. This review highlights the relationships between biosurfactant molecular composition, structure, and their interfacial behavior. It also describes how environmental factors such as temperature, pH, and ionic strength can impact physicochemical properties and self-assembly behavior of biosurfactant-containing solutions and dispersions. Comparison between biosurfactants and their synthetic counterparts are drawn to illustrate differences in their structure-property relationships and potential benefits. Knowledge of biosurfactant properties organized along these lines is useful for those seeking to formulate so-called green or natural products with novel and useful properties.