Production, characterization, and potential applications of lipopeptides in food systems: A comprehensive review

Lipopeptides are a class of lipid-peptide-conjugated compounds with differing structural features. This structural diversity is responsible for their diverse range of biological properties, including antimicrobial, antioxidant, and anti-inflammatory activities. Lipopeptides have been attracting the attention of food scientists due to their potential as food additives and preservatives. This review provides a comprehensive overview of lipopeptides, their production, structural characteristics, and functional properties. First, the classes, chemical features, structure-activity relationships, and sources of lipopeptides are summarized. Then, the gene expression and biosynthesis of lipopeptides in microbial cell factories and strategies to optimize lipopeptide production are discussed. In addition, the main methods of purification and characterization of lipopeptides have been described. Finally, some biological activities of the lipopeptides, especially those relevant to food systems along with their mechanism of action, are critically examined.

Biosurfactant-Assisted Cu Doping of Brushite Coatings: Enhancing Structural, Electrochemical, and Biofunctional Properties

Stainless steel (316L SS) has been widely used in orthopedic, cardiovascular stents, and other biomedical implant applications due to its strength, corrosion resistance, and biocompatibility. To address the weak interaction between steel implants and tissues, it is a widely adopted strategy to enhance implant performance through the application of bioactive coatings. In this study, Cu-doped brushite coatings were deposited successfully through pulse electrodeposition on steel substrates facilitated with a biosurfactant (BS) (i.e., surfactin). Further, the combined effect of various concentrations of Cu ions and BS on the structural, electrochemical, and biological properties was studied. The X-ray diffraction (XRD) confirms brushite composition with Cu substitution causing lattice contraction and a reduced crystallite size. The scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) studies reveal the morphological changes of the coatings with the incorporation of Cu, which is confirmed by X-ray photoelectron spectroscopy (XPS) and elemental mapping. The Fourier transform infrared (FTIR) and Raman spectroscopy confirm the brushite and Cu doping in the coatings, respectively. Increased surface roughness and mechanical properties of Cu-doped coatings were analyzed by using atomic force microscopic (AFM) and nanohardness tests, respectively. Electrochemical assessments demonstrate corrosion resistance enhancement in Cu-doped coatings, which is further improved with the addition of biosurfactants. In vitro biomineralization studies show the Cu-doped coating's potential for osseointegration, with added stability. The cytocompatibility of the coatings was analyzed using live/dead and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays; cell adhesion, proliferation, and migration studies were evaluated using SEM. Antibacterial assays highlight significant improvement in the antibacterial properties of Cu-doped coatings with BS. Thus, the developed Cu-doped brushite coatings with BS demonstrate their potential in the realm of biomedical implant technologies, paving the way for further exploration.

Structure and stability analysis of antibacterial substance produced by selenium enriched Bacillus cereus BC1

Microorganisms can produce many antibiotics against bacteria and fungi, which have been used as a potential choice of new antibiotics. In this paper, we studied the characteristics of antibacterial substances by Bacillus cereus BC1. The results showed that the acid-precipitated substance played the main role in antibacterial activity, and further characterization indicated that the antibacterial substance might be a lipopeptide substance. Then the antibacterial spectrum suggested that the antibacterial substance had an inhibitory effect on Gram-positive bacteria and fungi, while selenium-riched antibacterial substance of Bacillus cereus BC1 could significantly enhance the inhibition. Then the morphological effects of the antibacterial substance to indicator bacteria were determined. The effects of different treatment methods on the stability of antibacterial substances were studied and the results showed that the antibacterial substance was stable to heat, ultrasonic, and ultraviolet treatment, and their antibacterial activity would not be greatly affected. However, they were sensitive to pepsin. The optimum pH range of antibacterial activity was 3-5. This study may contribute to reusing the fermentation supernatant often discarded in the previous fermentation process. At the same time, the lipopeptide antibacterial substance extracted from the fermentation broth of selenium-enriched Bacillus cereus BC1 can be used in the development of antibiotics and biopesticides, and open up a new way for the control of plant diseases.

Identification and Characterization of Lipopeptide Biosurfactant Producing Microbacterium sp Isolated from Brackish River Water

BACKGROUND

Bioremediation has taken its call for removing pollutants for years. The oilcontaminated surroundings are majorly hazardous for sustaining life, but a great contribution to nature in the form of microorganisms. The complex carbon-hydrogen chain has served as classic raw material to chemical industries, which has perked up the hydrocarbon waste. Microbial remediation has been thus, focused to deal with the lacuna, where the new addition to this category is Microbacterium species.

OBJECTIVES

The identification and characterization of lipopeptide biosurfactant producing Microbacterium spp. isolated from brackish river water.

METHODS

The strain was isolated from an oil-contaminated lake. The strain was tested with all the other isolated species for oil degradation using screening protocols such as haemolysis, oil spread assay, BATH, E24, etc. The produced biosurfactant was extracted by acid precipitation, followed by solvent recovery. The strain with maximum potential was sequenced and was subjected to phylogeny assessment using in silico tools.

RESULTS

Novel Microbacterium species produce the extracellular biosurfactant. The surface tension of Microbacterium was found to be 32mN/m, indicates its powerful surface tension-reducing property. The strain was optimized for the production of biosurfactant and the best results were obtained with sucrose (2%) and yeast extract (3%) medium at 7 pH and 40°C temperature.

CONCLUSION

The isolate was confirmed to be a novel Microbacterium species that could produce 0.461 gm biosurfactant in 100 ml of the medium throughout a life cycle and novel strain of isolate was deposited to NCBI as Microbacterium spp. ANSKSLAB01 using an accession number: KU179507.

Insecticidal Activity of Bacteria from Larvae Breeding Site with Natural Larvae Mortality: Screening of Separated Supernatant and Pellet Fractions

Mosquitoes can transmit to humans devastating and deadly pathogens. As many chemical insecticides are banned due to environmental side effects or are of reduced efficacy due to resistance, biological control, including the use of bacterial strains with insecticidal activity, is of increasing interest and importance. The urgent actual need relies on the discovery of new compounds, preferably of a biological nature. Here, we explored the phenomenon of natural larvae mortality in larval breeding sites to identify potential novel compounds that may be used in biological control. From there, we isolated 14 bacterial strains of the phylum Firmicutes, most of the order Bacillales. Cultures were carried out under controlled conditions and were separated on supernatant and pellet fractions. The two fractions and a 1:1 mixture of the two fractions were tested on L3 and early L4 Aedes albopictus. Two concentrations were tested (2 and 6 mg/L). Larvae mortality was recorded at 24, 48 and 72 h and compared to that induced by the commercialized B. thuringiensis subsp. israelensis. Of the 14 strains isolated, 11 were active against the A. albopictus larvae: 10 of the supernatant fractions and one pellet fraction, and mortality increased with the concentration. For the insecticide activity prediction in three strains of the Bacillus cereus complex, PCR screening of the crystal (Cry) and cytolytic (Cyt) protein families characteristic to B. thuringiensis subsp. israelensis was performed. Most of the genes coding for these proteins' synthesis were not detected. We identified bacterial strains that exhibit higher insecticidal activity compared with a commercial product. Further studies are needed for the characterization of active compounds.

Increase in bacterial biosurfactant production by co-cultivation with biofilm-forming bacteria

Considering that bacterial biosurfactants (BSFs) are released as secondary metabolites involved in biotic relations within mixed bacterial assemblages, the hypothesis that the co-cultivation of BSF producing bacteria with biofilm-forming strains would enhance BSF synthesis was tested. Environmental BSF producing strains of Bacillus licheniformis and Pseudomonas sp. were cultivated with reference biofilm-forming strains (Pseudomonas aeruginosa and Listeria innocua). BSF production and quorum-quenching effects were tested in solid media. Tensioactive and anionic BSFs were also quantified in cell-free extracts (CFEs). BSF production increased in co-cultures with inducer strains although this was not demonstrated by all screening methods. Increased concentrations of anionic BSF were detected in CFEs of co-cultures in which Pseudomonas aeruginosa was included as inducer, which is in accordance with the observation of larger halos in cetyl trimethylammonium bromide-methylene blue agar. The results demonstrate that co-cultivation positively affects the efficiency of BSF production and that higher production yields may be attained by selecting convenient inducer partners in designed consortia. SIGNIFICANCE AND IMPACT OF THE STUDY: The high production cost of biosurfactants (BSFs) still represents a major limitation to the industrial use of these otherwise advantageous alternatives to chemical surfactants. This work demonstrates that the co-cultivation of consortia of biosurfactant-producer and biofilm-forming bacteria enhances BSF production and may contribute to the cost-effectiveness of biosurfactant-based products.

Production of a biosurfactant from Bacillus methylotrophicus UCP1616 for use in the bioremediation of oil-contaminated environments

The aim of the present study was to produce a microbial biosurfactant for use in the bioremediation of environments contaminated with petroleum products. Bacillus methylotrophicus was isolated from seawater taken from a port area and cultivated using industrial waste as substrate (corn steep liquor and sugarcane molasses [both at 3%]). Surface tension measurements and motor oil emulsification capacity were used for the evaluation of the production of the biosurfactant, which demonstrated stability in a broad range of pH and temperature as well as a high concentration of saline, with the reduction of the surface tension of water to 29 mN/m. The maximum concentration of biosurfactant (10.0 g/l) was reached after 144 h of cultivation. The biosurfactant was considered to be a lipopeptide based on the results of proton nuclear magnetic resonance and Fourier transformed infrared spectroscopy. The tests demonstrated that the biosurfactant is innocuous and has potential for the bioremediation of soil and water contaminated by petroleum products. Thus, the biosurfactant described herein has a low production cost and can be used in environmental processes.

Isolation and characterization of biosurfactant-producing and diesel oil degrading Pseudomonas sp. CQ2 from Changqing oil field, China

In the present research investigation, 13 indigenous bacteria (from CQ1 to CQ13) were isolated from soil collected from Changqing oil field of Xi'an, China. Four promising biosurfactant producers (CQ1, CQ2, CQ4, and CQ13) were selected through primary screening among these 13 strains, including via drop collapse and oil-spreading methods. However, only the strain CQ2 showed the best biosurfactant production and was further screened by hemolytic assay, cetyl trimethyl ammonium bromide (CTAB), surface tension and emulsifying activity. The bacterium CQ2 has the ability to produce about 3.015 g L-1 of biosurfactant using glucose as the sole carbon source without any optimization. The produced biosurfactant could greatly reduce surface tension from 72.66 to 24.72 mN m-1 with a critical micelle concentration (CMC) of 30 mg L-1 and emulsify diesel oil up to 60.1%. The cell-free broth was found to be stable in wide temperature (4-100 °C), pH (6-12) and salinity (2-20%) ranges for surface and emulsifying activity. This biosurfactant was preliminarily found to be of a glycolipid nature as evident from thin-layer chromatographic (TLC) and Fourier transform infra-red spectroscopic (FTIR) analyses. Moreover, CQ2 was able to degrade 54.7% of diesel oil, which surprisingly could form a substantial amount of bioflocculants during the degradation process. Furthermore, the 16S rDNA sequence using the Genbank BLAST tool revealed that isolated CQ2 was closely related to species of Pseudomonas genus and, thus, was entitled Pseudomonas sp. CQ2. The results of residual diesel oil contents measured by GC-MS showed that C7-C28 hydrocarbons could be degraded by Pseudomonas sp. CQ2. Thus, these findings revealed that CQ2 could be applied for remediation of diesel oil/petroleum-contaminated waters and soils on a large scale.

Investigation of the structural, physicochemical properties, and aggregation behavior of lipopeptide biosurfactant produced by Acinetobacter junii B6

In the present study the produced biosurfactant of Acinetobacter junii B6 (recently isolated from Iranian oil excavation site) were partially purified and identified by high performance thin layer chromatography (HPTLC), Fourier transform infrared spectroscopy (FTIR), and proton nuclear magnetic resonance (¹H NMR). Elemental analysis of the biosurfactant by energy dispersive X-ray spectroscopy (EDS) revealed that the biosurfactant was anionic in nature. The physiochemical properties of the lipopeptide biosurfactant were evaluated by determination of its critical micelle concentration (CMC) and hydrophile-lipophile balance (HLB). The produced biosurfactant decreased the surface tension of water to 36mNm^-1 with the CMC of approximately 300mg/l. Furthermore, the solubility properties of the biosurfactant (dissolved in phosphate-buffer saline solution, pH7.4) were investigated by turbidity examination, dynamic light scattering (DLS) measurements, and transmission electron microscopy (TEM) inspection. It could be concluded that the biosurfactant showed the spherical-shaped vesicles at a concentration higher than its CMC and the circular dichroism (CD) spectra showed that the secondary structure of the biosurfactant vesicles is dominated by the β sheet.

Biosurfactants in cosmetic formulations: trends and challenges

Cosmetic products play an essential role in everyone's life. People everyday use a large variety of cosmetic products such as soap, shampoo, toothpaste, deodorant, skin care, perfume, make-up, among others. The cosmetic industry encompasses several environmental, social and economic impacts that are being addressed through the search for more efficient manufacturing techniques, the reduction of waste and emissions and the promotion of personal hygiene, contributing to an improvement of public health and at the same time providing employment opportunities. The current trend among consumers is the pursuit for natural ingredients in cosmetic products, as many of these products exhibit equal, better or additional benefits in comparison with the chemical-based products. In this sense, biosurfactants are natural compounds with great potential in the formulation of cosmetic products given by their biodegradability and impact in health. Indeed, many of these biosurfactants could exhibit a "prebiotic" character. This review covers the current state-of-the-art of biosurfactant research for cosmetic purposes and further discusses the future challenges for cosmetic applications.

Surfactin-functionalized poly(methyl methacrylate) as an eco-friendly nano-adsorbent: from size-controlled scalable fabrication to adsorptive removal of inorganic and organic pollutants

Green synthesis of poly(methyl methacrylate) nanoparticles functionalized with the biosurfactant surfactin for adsorptive and reusable removal of toxic metals and organic compounds.

Isolation and purification of a new enamide biosurfactant from Fusarium proliferatum using rice-bran

A new fungusFusarium proliferatumwas isolated from the oil contaminated sludge of the rice-bran oil industry, which was capable of producing biosurfactants when grown on rice-bran.

Physiochemical and thermodynamic characterization of lipopeptide biosurfactant secreted by Bacillus tequilensis HK01

An extensive investigation was applied to isolate biosurfactant producing bacteria from urban waste.

Biodegradation of 2,4-dinitrotoluene with Rhodococcus pyridinivorans NT2: characteristics, kinetic modeling, physiological responses and metabolic pathway

Physiological responses ofRhodococcus pyridinivoransNT2 and elucidation of metabolic intermediates formed during biodegradation of 2,4-DNT.

Hydrocarbon degradation by a newly isolated thermophilic Anoxybacillus sp. with bioemulsifier production and new alkB genes

In this work, a new thermophilic bacterial strain was isolated and identified asAnoxybacillussp. WJ-4. This strain of WJ-4 can degrade a wide range of hydrocarbons, and production of an oligosaccharide–lipid–peptide bioemulsifier was detected.