Circulocins, new antibacterial lipopeptides from Bacillus circulans , J2154

An insight into the utilization of microbial biosurfactants pertaining to their industrial applications in the food sector

Microbial biosurfactants surpass synthetic alternatives due to their biodegradability, minimal toxicity, selective properties, and efficacy across a wide range of environmental conditions. Owing to their remarkable advantages, biosurfactants employability as effective emulsifiers and stabilizers, antimicrobial and antioxidant attributes, rendering them for integration into food preservation, processing, formulations, and packaging. The biosurfactants can also be derived from various types of food wastes. Biosurfactants are harnessed across multiple sectors within the food industry, ranging from condiments (mayonnaise) to baked goods (bread, muffins, loaves, cookies, and dough), and extending into the dairy industry (cheese, yogurt, and fermented milk). Additionally, their impact reaches the beverage industry, poultry feed, seafood products like tuna, as well as meat processing and instant foods, collectively redefining each sector's landscape. This review thoroughly explores the multifaceted utilization of biosurfactants within the food industry as emulsifiers, antimicrobial, antiadhesive, antibiofilm agents, shelf-life enhancers, texture modifiers, and foaming agents.

Taeanamides A and B, Nonribosomal Lipo-Decapeptides Isolated from an Intertidal-Mudflat-Derived Streptomyces sp

Two new lipo-decapeptides, namely taeanamides A and B (1 and 2), were discovered from the Gram-positive bacterium Streptomyces sp. AMD43, which was isolated from a mudflat sample from Anmyeondo, Korea. The exact molecular masses of 1 and 2 were revealed by high-resolution mass spectrometry, and the planar structures of 1 and 2 were elucidated using NMR spectroscopy. The absolute configurations of 1 and 2 were determined using a combined analysis of ¹H-¹H coupling constants and ROESY correlations, the advanced Marfey’s method, and bioinformatics. The putative nonribosomal peptide synthetase pathway for the taeanamides was identified by analyzing the full genome sequence data of Streptomyces sp. AMD43. We also found that taeanamide A exhibited mild anti-tuberculosis bioactivity, whereas taeanamide B showed significant bioactivity against several cancer cell lines.

Identification of fusaricidins from the antifungal microbial strain Paenibacillus sp. MS2379 using ultra-high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry

Paenibacillus sp. MS2379 is a highly efficient microbial strain producing fusaricidins, a class of lipopeptides that have demonstrated strong antifungal activities against a broad array of fungal pathogens. An integrated approach combining chromatographic fractionation, UHPLC-QTOF-MS analysis, and NMR spectroscopic interpretation was employed to characterize antifungal metabolites produced by this microbial strain, resulting in the identification of 48 fusaricidins including 30 cyclic and 18 open-chain species. In this regard, UHPLC-QTOF-MS played a vital role in determining structures of 28 new fusaricidins through peptide fragment analysis. The structural determination of the new fusaricidins by the high-resolution mass spectrometry was validated by follow-up isolation and NMR spectroscopic analysis of representative compounds. It is worth noting that novel fusaricidins with amino acid residues of serine and γ-aminobutyric acid were identified, which is of great biosynthetic significance for this biologically important class of compounds. The present study again illustrates the power of UHPLC-QTOF-MS for structural identification of lipopeptides, and the structural diversity of the identified fusaricidins makes this microbial strain unique as a potential biocontrol agent.

Bacillaceae-derived peptide antibiotics since 2000

Members of the Bacillaceae family, including Bacillus spp., Brevibacillus spp., Paenibacillus spp., Aneurinibacillus sp., and Halobacillus sp., are an important source of structurally diverse classes of short peptides of ∼ 30 residues or fewer possessing peculiar and rapid killing activity against various pathogens. Additionally, many have unique structures that enhance resistance to hydrolysis by proteases, and these are ideal therapeutic tools and potential alternatives to current antibiotics. The need for novel antibiotic lead compounds is urgent, and this review summarises 119 Bacillaceae compounds published since 2000, including 12 surfactin-like lipopeptides, 16 iturinic lipopeptides, fengycin C, 33 other cyclic lipopeptides, 26 linear lipopeptides, two thiopeptides, four 2,5-diketopiperazines, 20 typical cyclic peptides, and five standard linear peptides. The current and potential therapeutic applications of these peptides, including structure, antibacterial, antifungal, and antiviral activities, are discussed.

The chemistry and biology of guanidine natural products

The chemistry and biology of natural guanidines isolated from microbial culture media, from marine invertebrates, as well as from terrestrial plants and animals, are reviewed.

Review lipopeptides biosurfactants: Mean classes and new insights for industrial, biomedical, and environmental applications

Lipopeptides are microbial surface active compounds produced by a wide variety of bacteria, fungi, and yeast. They are characterized by high structural diversity and have the ability to decrease the surface and interfacial tension at the surface and interface, respectively. Surfactin, iturin, and fengycin of Bacillus subtilis are among the most popular lipopeptides. Lipopepetides can be applied in diverse domains as food and cosmetic industries for their emulsification/de-emulsification capacity, dispersing, foaming, moisturizing, and dispersing properties. Also, they are qualified as viscosity reducers, hydrocarbon solubilizing and mobilizing agents, and metal sequestering candidates for application in environment and bioremediation. Moreover, their ability to form pores and destabilize biological membrane permits their use as antimicrobial, hemolytic, antiviral, antitumor, and insecticide agents. Furthermore, lipopeptides can act at the surface and can modulate enzymes activity permitting the enhancement of the activity of certain enzymes ameliorating microbial process or the inhibition of certain other enzymes permitting their use as antifungal agents. This article will present a detailed classification of lipopeptides biosurfactant along with their producing strain and biological activities and will discuss their functional properties and related applications.

Genetic regulations of the biosynthesis of microbial surfactants: an overview

Microbial biosurfactants are surface active metabolites synthesized by microbes growing on a variety of substrates. In spite of having great potential for commercial, therapeutic and environmental applications, industrial level production has not been realized for their low yields and productivities. One vital factor determining their biosynthesis is the genetic makeup of the producer organisms. Studies on molecular genetics and biochemistry of the synthesis of several biosurfactants have revealed the operons, the enzymes and the metabolic pathways required for their extracellular production. Surfactin, a cyclic lipopeptide biosurfactant is a potent antimicrobial agent and is produced as a result of non-ribosomal biosynthesis catalyzed by a large multienzyme peptide synthetase complex called the surfactin synthetase. Pathways for the synthesis of other lipopeptides such as iturin, lichenysin and arthrofactin are also mediated by similar enzyme complexes. These non-ribosomal peptide synthetases (NRPSs) responsible for lipopeptide biosynthesis display a high degree of structural similarity among themselves even from distant microbial species. Plasmid-encoded- rhlA, B, R and I genes of rhl quorum sensing system are required for production of glycolipid biosurfactants by Pseudomonas species. Molecular genetics of biosynthesis of alasan and emulsan by Acinetobacter species and of the fungal biosurfactants such as mannosylerythritol lipids (MEL) and hydrophobins have been deciphered. However, limited genetic information is available about biosynthesis of other biosurfactants such as viscosin, amphisin and putisolvin produced by some strains of Pseudomonas species. Understanding of the genetic regulatory mechanisms would help to develop metabolically engineered hyper-producing strains with better product characteristics and acquired capability of utilizing cheap agro-industrial wastes as substrates. This article thus provides an overview of the role and importance of molecular genetics and gene regulation mechanisms behind the biosynthesis of various microbial surfactants of commercial importance.

Diversity of nonribosomal peptide synthetases involved in the biosynthesis of lipopeptide biosurfactants

Lipopeptide biosurfactants (LPBSs) consist of a hydrophobic fatty acid portion linked to a hydrophilic peptide chain in the molecule. With their complex and diverse structures, LPBSs exhibit various biological activities including surface activity as well as anti-cellular and anti-enzymatic activities. LPBSs are also involved in multi-cellular behaviors such as swarming motility and biofilm formation. Among the bacterial genera, Bacillus (Gram-positive) and Pseudomonas (Gram-negative) have received the most attention because they produce a wide range of effective LPBSs that are potentially useful for agricultural, chemical, food, and pharmaceutical industries. The biosynthetic mechanisms and gene regulation systems of LPBSs have been extensively analyzed over the last decade. LPBSs are generally synthesized in a ribosome-independent manner with megaenzymes called nonribosomal peptide synthetases (NRPSs). Production of active-form NRPSs requires not only transcriptional induction and translation but also post-translational modification and assemblage. The accumulated knowledge reveals the versatility and evolutionary lineage of the NRPSs system. This review provides an overview of the structural and functional diversity of LPBSs and their different biosynthetic mechanisms in Bacillus and Pseudomonas, including both typical and unique systems. Finally, successful genetic engineering of NRPSs for creating novel lipopeptides is also discussed.

Determination of the structure of the fatty acid chain in a cyclic lipopeptide using GC-MS

A GC-EIMS method to determine the structure of the fatty acid chains in cyclic lipopeptides is described. The structure of the fatty acid chains can be determined by the characteristic peaks of the MS spectrogram according to the fact that the alpha cleavage predominates the MS of a fatty acid with amino and hydroxy groups, while the McLafferty rearrangement predominates the MS of one without amino or hydroxy group. The characteristics of the strongest peaks of 103 and 102 in MS spectrograms due to alpha cleavage represent the beta-hydroxy-fatty acid and the beta-amino fatty acid, respectively; the strongest peak of 117 due to alpha cleavage and the relatively weak peak of 88 due to McLafferty rearrangement indicate the beta-hydroxy-fatty acid with a branched methyl group at its alpha position. The strongest peak of 74 due to McLafferty suggests the fatty acid without hydroxy or amino group. The ratio of relative intensity (I(43)/I(57)) characterizes the branches of alkyl chains. The greater I(43)/I(57) corresponds to an iso alkyl, and the smaller I(43)/I(57) corresponds to an anteiso alkyl. This method can be used to determine the full structure of the fatty acid chains in lipopeptides.

Isolation of Heptadepsin, a Novel Bacterial Cyclic Depsipeptide that Inhibits Lipopolysaccharide Activity

Lipopolysaccharide (LPS) is considered to cause various inflammatory reactions. We searched among microbial secondary metabolites for compounds that could inhibit LPS-stimulated adhesion between human umbilical vein endothelial cells (HUVEC) and human myelocytic cell line HL-60 cells. In the course of our screening, we isolated a novel cyclic depsipeptide, which we named heptadepsin, from the whole culture broth of Paenibacillus sp. The addition of heptadepsin prior to LPS stimulation decreased HL-60 cell-HUVEC adhesion without showing any cytotoxicity. It also inhibited the cellular adhesion induced by lipid A, the active component of LPS, but it did not inhibit TNF-alpha or IL-1beta-induced cell adhesion. The result of surface plasmon resonance (SPR) analysis revealed that heptadepsin interacted with lipid A directly. Thus, heptadepsin, a novel naturally occurring cyclic heptadepsipeptide, was shown to inactivate LPS by direct interaction with LPS.