Aims: Bacillus amyloliquefaciens lipopeptide are made of amino acids and fatty acid chain, and have many antifungal activities against several important pathogenic yeasts. The present research was carried out with the aim of extraction and evaluation of antifungal effect of lipopeptide compounds produced by Esfahan native Bacillus amyloliquefaciens M13RW01 against Candida albicans, Candida glabrata, Candida krusei, Candida parapsilosis, and Candida tropicalis.
In this experimental study, Bacillus amyloliquefaciens M13RW01 was cultured in modified Peptone-Glucose-Yeast extract medium (PGY) for 72 hours. Then, the lipopeptide compounds produced in the medium by precipitation with HCl 6M were extracted and dissolved in methanol (50% water; 50% methanol). The antifungal activity of lipopeptide compounds against 5 species of Candida was investigated by well diffusion method, Minimum Inhibitory Concentration (MIC), and Minimum Fungal Concentration (MFC). Also, germ tube production by Candida albicans in tube containing lipopeptide was investigated.
Findings: The Bacillus amyloliquefaciens M13RW01 lipopeptide metabolites inhibited germ tube production in all C. albicans yeasts, but no inhibitory or fatal effect was observed on other species of Candida. Inhibition zone was not observed around the wells; in all dilutions, Candida yeasts grew. Therefore, minimal inhibitory concentration and minimal fungicidal concentration were not determined.
The lipopeptide metabolites produced by Bacillus amyloliquefaciens M13RW01 have no inhibitory or fungal effects on the studied species of Candida, but inhibit the germ tubes production by Candida albicans yeast.

In humans, during the recent years, several factors have increased the risk of fungal infections, like broad spectrum antibiotics, immune compromised patients, cytotoxic chemotherapy and transplantations. Among all fungal pathogens Candida species remain the most common cause of invasive fungal infections. The aim of the current study is extraction of lipopeptides from Bacillus atrophaeus HNSQJYH170 isolated from Isfahan, and the study of its antifungal effects against Candida species.
After 72 h of incubation, a cell-free supernatant of Bacillus atrophaeus was collected by centrifugation and acidified by adding HCl. The precipitate obtained was collected by centrifugation and dissolved in the methanol solution (50 ). Then antifungal activity of lipopeptides was evaluated by well diffusion method against Candida species. Also inhibition effect of lipopeptide on germ tube production for Candida albicans was studied.
There was no Inhibition zone for Candida species by cyclic lipopeptides. Inhibition of germtube production in %95 of C.albicans cells was showed by Bacillus atrophaeus lipopeptides.
The results of this study showed that, although lipopeptides extracted from Bacillus atrophaeus were not able to inhibit Candida spp but inhibition of germtube production in %95 of C.albicans cells was showed. The ability of lipopeptides in inhibition of germtube production in C.albicans was showed, that these compounds can prevent biofilm formation on catheters and other substrate. Therefore, these compounds are important in preventing the invasion C.albicans of mucosal.

Members of the genus Bacillus are among the most promising candidates for biological control of plant pathogenic bacteria. In this study, cell free supernatants of three strains B. subtilis UTB96, B. subtilis UTB1 and B. subtilis UTB70 against Aspergillus flavus R5 were investigated using dual culture assay. Strain B. subtilis UTB96 showed the highest inhibition effect. Thin lyer chromatography in extracted lipopeptides of the bacterial cell free supernatants proved the presence of the three families of lipopeptides iturin, fengycin and surfactin. Bioautography analysis of the chromatogarams against A. flavus R5 revealed the antifungal potential of iturins in strain B. subtilis UTB96. Gene bymB (the third gene in iturin biosynthesis) was disrupted usisng targeted mutagenesis to confirm role of iturins in antifungal activity. Molecular study (PCR analysis and sequencing the amplified fragment) of the mutants revealed that the targeted gene (bmyB) was replaced by spectinomycin resistance gene, hence the gene was disrupted. The phenotypical comparison of the bmyB mutants with the parental strain demonstrated that the antifungal activity of cell free supernatants and extracted lipopeptides was decreased interestingly in a dual culture assay with A. flavus, bioautography analysis and also on pistachio nuts. To sum up, these findings allowed us to conclude that iturin-like lipopeptides are indispensable for the biocontrol ability of the strain UTB96 against A. flavus R5.

The multi-drug resistant bacteria and clinical infections are some of the biggest global concerns, so new drugs are needed. Antimicrobial peptides and lipopeptides are new bioactive agents with great potential that can become a new strategy for clinical applications.

Some Bacillus strains were isolated based on hemolytic antimicrobial production from the soil. The extracellular proteins were extracted by acidic precipitation and chloroform/methanol method and analyzed by SDS-PAGE electrophoresis and stained with Sudan black. The black fragment was purified and characterized by FTIR, GC/MS, and HPLC analysis to demonstrate the presence of lipids and proteins. The anti-microbial ability and stability of the purified lipopeptide were assayed by the Kirby-Bauer method. Also, it was examined for metal removal.

A new Bacillus halotolerans strain SCM 034 with hemolytic antimicrobial production was isolated. According to GC/MS (detecting C16, C17) and HPLC (detecting leucine, glutamic acid, valine, arginine, glycine, and aspartic acid) data, the black fragment was lipopeptide. Polyacrylamide hydrogel containing lipopeptide and gel purified lipopeptide showed anti-microbial activities against S. aureus and S. cerevisiae that were stable for a few months. Also, the lipopeptide was useful for cation removal and decreased cobalt, nickel, and calcium by 10.81 %, 24.39 %, and 34 %, respectively.

Production of antibacterial lipopeptide hemolysin from this strain is reported for the first time and according to the results, lipopeptides have unique properties with biomedical and pharmaceutical applications. Also, polyacrylamide hydrogel lipopeptide is a promising candidate for wound healing.

Bacillus mojavensis PTCC 1696 (a member of Bacillus subtilis group) has been isolated from the Iranian oil field (Masjed-I Soleyman), to examine its ability to produce biosurfactant (lipopeptide type) [28]. The present study was designed to characterize the antibacterial activity of the isolated biosurfactant. The antibacterial activity towards several bacteria including clinical isolates and type strains species was examined. For detecting the extent of antibacterial activity, the agar disc diffusion method was used, where the measured diameter of the zone of inhibition was used as an index for determining the antibacterial activity. Among the test microorganisms, the antibacterial activity was highest in Pseudomonas aeruginosa ATCC 27853. At concentration as low as 16 μg/ml, the inhibitory effect of the lipopeptide biosurfactant was detectable. The stability of the test biosurfactant also was examined over a wide range of temperatures (40–100°C)and pH values (2-11). The stability was further tested using protease and lipase, where the substance showed clear sensitivity towards lipase. The potentiality of this antibacterial agent in clinical applications is of interest and needs to be further recognized.

 Lipopeptides are potential microbial metabolites that are abandoned with broad spectrum biopharmaceutical properties ranging from antimicrobial, antiviral and anticancer, etc. Clinical studies are not much explored beyond the experimental methods to understand drug mechanisms on target proteins at the molecular level for large molecules. Due to the less available studies on potential target proteins of lipopeptide based drugs, their potential inhibitory role for more obvious treatment on disease have not been explored in the direction of lead optimization. However, Computational approaches need to be utilized to explore drug discovery aspects on lipopeptide based drugs, which are time saving and cost-effective techniques.

 Here a ligand-based drug discovery approach is coupled with reverse pharmacophore-mapping for the prediction of potential targets for antiviral (SARS-nCoV-2) and anticancer lipopeptides. Web-based servers PharmMapper and SwissTargetPrediction are used for the identification of target proteins for lipopeptides surfactin and iturin produced by Bacillus subtilis.

 The studies have given the insight to treat the diseases with next-generation large molecule therapeutics. Results also indicate the affinity for Angiotensin-Converting Enzymes (ACE) and proteases as the potential viral targets for these categories of peptide therapeutics. A target protein for the Human Papilloma Virus (HPV) has also been mapped.

 The work will further help in exploring computer-aided drug designing of novel compounds with greater efficiency where the structure of the target proteins and lead compounds are known.

Fluorescent pseudomonads are an effective source of biological control that have high adaptive power and able to produce a wonderful source of secondary metabolites. Antibiotics such as phenazines, diacetylphloroglucinol, and hydrogen cyanide are produced by certain taxonomic groups of the genus Pseudomonas and appear to be ancestral. These compounds often play a physiological role in producing strain, independent of their antibiotic activity. Other secondary metabolites including rhizoxins, promysalin, L- Furanomycin, insect toxins, and biosurfactants (rhamnolipids and cyclic lipopeptides) are only found in certain Pseudomonas isolates. Recent advances in genome sequencing have led to the discovery of a large number of cryptic biosynthetic gene clusters. Genome mining has led to the discovery of many antimicrobial compounds that have the biocontrol role in the plant-pathogenic fungi, oomycetes and bacteria. In addition, some biocontrol strains of Pseudomonas can produce anti-insect compounds. The ability of Pseudomonas biocontrol agents continues to surprise. This paper tries to investigate the latest studies about biocontrol mechanisms of fluorescent pseudomonads.

 Surfactin is a cyclic heptapeptide that is closed by a β-hydroxy fatty acid chain. This potent biosurfactant is produced by different Bacillus subtilis strains. This lipopeptide has numerous attractive biological activities, including antibacterial, antiviral, antimycoplasma, hemolytic, and other different and powerful surface and interface activities.

 Understanding how surfactin binds to different membranes and its mechanism of action can help us modify and optimize its structure to improve the potential efficacy of this lipopeptide in the future. For this purpose, we studied the interaction of this lipopeptide with two types of lipid bilayer models, including palmitoyl-oleoyl-glycero- phosphocholine (POPC) and palmitoyl-oleoyl-phosphtidylglycerol (POPG) as the prokaryotic and eukaryotic membrane models, respectively.

 The obtained data have shown that the tendency of surfactin for these membranes is different. According to the analysis, this molecule binds to both membranes peripherally, and its interaction with the negative membrane is also more potent compared to the zwitterionic membrane. Moreover, we found that surfactin destabilized POPG more than POPC. This suggests that surfactin may act by modifying the membrane’s bulk physical properties.

 As a final point, this study has shown that surfactin has different behaviors in the eukaryotic and prokaryotic cell membranes and can modify and amplify its action in order to use it for antibacterial drugs.

Computer-aided drug designing is a promising approach to defeating the dry pipeline of drug discovery. It aims at reduced experimental efforts with cost-effectiveness. Naturally occurring large molecules with molecular weight higher than 500 Dalton such as cationic peptides, cyclic peptides, glycopeptides and lipopeptides are a few examples of large molecules which have successful applications as the broad spectrum antibacterial, anticancer, antiviral, antifungal and antithrombotic drugs. Utilization of microbial metabolites as potential drug candidates incur cost effectiveness through large scale production of such molecules rather than a synthetic approach. Computational studies on such compounds generate tremendous possibilities to develop novel leads with challenges to handle these complex molecules with available computational tools. The opportunities begin with the desired structural modifications in the parent drug molecule. Virtual modifications followed by molecular interaction studies at the target site through molecular modeling simulations and identification of structure-activity relationship models to develop more prominent and potential drug molecules. Lead optimization studies to develop novel compounds with increased specificity and reduced off targeting is a big challenge computationally for large molecules. Prediction of optimized pharmacokinetic properties facilitates development of a compound with lower toxicity as compared to the natural compounds. Generating the library of compounds and studies for target specificity and ADMET (Absorption, Distribution, Metabolism, Excretion and Toxicity) for large molecules are laborious and incur huge cost and chemical wastage through in-vitro methods. Hence, computational methods need to be explored to develop novel compounds from natural large molecules with higher specificity. This review article is focusing on possible challenges and opportunities in the pathway of computeraided drug discovery of large molecule therapeutics.

Biosurfactants are derived from microbes, plants, and animals. Acinetobacter junii B6 is a lipopeptide biosurfactant producer previously investigated for its structure, physicochemical, and product aggregation properties.

In this study, we investigated and optimized the bioencapsulation of A. junii B6 in calcium alginate hydrogel.

A. junii B6 was encapsulated using calcium alginate hydrogel. The formulation of the hydrogel was optimized using a full factorial approach. Sodium alginate concentration, calcium chloride concentration, and hardening time were selected as the main factors, and surface tension was the response measure. A scanning electron microscope (SEM) was used to study the bead’s morphology.

Scanning electron microscope image showed rounded and smooth beads. The most biosurfactant production and reduced surface tension (35.98 mN/m) were observed at concentrations of 1% calcium chloride, (1%) sodium alginate, and 15 minutes of hardening time. A. junii B6 can be encapsulated in alginate hydrogels producing biosurfactant at optimum experimental design.

This represents a practical method for optimizing the bioencapsulation of A. junii B6 to produce biosurfactants.