Production of surfactin from Bacillus subtilis MZ-7 grown on pharmamedia commercial medium

Investigating the mechanism of interfacial tension reduction through the combination of low-salinity water and bacteria

In the enhanced oil recovery (EOR) process, interfacial tension (IFT) has become a crucial factor because of its impact on the recovery of residual oil. The use of surfactants and biosurfactants can reduce IFT and enhance oil recovery by decreasing it. Asphaltene in crude oil has the structural ability to act as a surface-active material. In microbial-enhanced oil recovery (MEOR), biosurfactant production, even in small amounts, is a significant mechanism that reduces IFT. This study aimed to investigate fluid/fluid interaction by combining low biosurfactant values and low-salinity water using NaCl, MgCl2, and CaCl2 salts at concentrations of 0, 1000, and 5000 ppm, along with Geobacillus stearothermophilus. By evaluating the IFT, this study investigated different percentages of 0, 1, and 5 wt.% of varying asphaltene with aqueous bulk containing low-salinity water and its combination with bacteria. The results indicated G. Stearothermophilus led to the formation of biosurfactants, resulting in a reduction in IFT for both acidic and basic asphaltene. Moreover, the interaction between asphaltene and G. Stearothermophilus with higher asphaltene percentages showed a decrease in IFT under both acidic and basic conditions. Additionally, the study found that the interaction between acidic asphaltene and G. stearothermophilus, in the presence of CaCl2, NaCl, and MgCl2 salts, resulted in a higher formation of biosurfactants and intrinsic surfactants at the interface of the two phases, in contrast to the interaction involving basic asphaltene. These findings emphasize the dependence of the interactions between asphaltene and G. Stearothermophilus, salt, and bacteria on the specific type and concentration of asphaltene.

Characterization of Antimicrobial Peptide Produced by Bacillus Subtilis Subsp. Subtilis.. [DOI: 10.21203/rs.3.rs-2856256/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Purpose: Antimicrobial peptides are amongst the most promising class of peptides to contract the rise of global antimicrobial resistant. This article investigates a new antimicrobial peptide from bacteria.Methods: Bacterial identification was based on phenotypical and biochemical properties as well as 16S rRNA gene sequence homology. Bacterial growth and production of the inhibitory substance was standardized and optimized. The newly antimicrobial peptide was purified to homogeneity, subsequently analyzed by PAGE and MALDI-TOF-MS.Results: The bacterium identified as Bacillus subtilis subsp. subtilis and designated as strain MZ-32. Landy medium was best for the production when compared with different media after fixing the least influential variables in standardized fermentation conditions. Carbohydrate and nitrogen supplements investigated to improve production in Landy medium. The antimicrobial peptide of 2.158-Da was active against a broad range of skin-born pathogenic bacteria that were resistant to standard antibiotics, and possessed the physico-chemical properties of an ideal antimicrobial agent in terms of water solubility, thermal resistance, and stability towards acid/alkali (pH 4.0 to 9.0) treatments.Conclusion: The new strain and its associated peptide are potentially new candidates for medical and biotechnological applications.

Fermentation optimization of surfactin production of Bacillus amyloliquefaciens HM618

This work isolated a strain named Bacillus amyloliquefaciens HM618 from the soil, which can inhibit the growths of Botrytis cinerea, Rhizoctonia solani, and Escherichia coli DH5α. Based on the results of response surface methodology, the surfactin levels of strain HM618 were elevated from 0.724 to 1.876 g/L and 0.995 to 1.888 g/L under the pure culture with the optimized medium (containing 62.39 g/L sucrose, 15.06 g/L yeast extracts, and 3.27 g/L aspartate) and under the coculture of strains HM618 and Bacillus subtilis 168 with the optimized medium (containing 50.52 g/L sucrose, 19.76 g/L yeast extracts, and 1.02 g/L glutamate), respectively. Additionally, influences of nonconstitutive amino acids involved in the biosynthesis of surfactin were also explored. The highest surfactin level reached 2.04 g/L after adding 3.0 g/L exogenous ornithine. However, the surfactin production of strain HM618 was significantly inhibited after adding the mixtures of nonconstitutive amino acids.

Physiological and transcriptional profiling of surfactin exerted antifungal effect against Candida albicans

Given the risk of Candida albicans overgrowth in the gut, novel complementary therapies should be developed to reduce fungal dominancy. This study highlights the antifungal characteristics of a Bacillus subtilis-derived secondary metabolite, surfactin with high potential against C. albicans. Surfactin inhibited the growth of C. albicans following a 1-hour exposure, in addition to reduced adhesion and morphogenesis. Specifically, surfactin did not affect the level of reactive oxygen species but increased the level of reduced glutathione. Surprisingly, ethanol production was increased following 2 h of surfactin exposure. Surfactin treatment caused a significant reduction in intracellular iron, manganese and zinc content compared to control cells, whereas the level of copper was not affected. Alongside these physiological properties, surfactin also enhanced fluconazole efficacy. To gain detailed insights into the surfactin-related effects on C. albicans, genome-wide gene transcription analysis was performed. Surfactin treatment resulted in 1390 differentially expressed genes according to total transcriptome sequencing (RNA-Seq). Of these, 773 and 617 genes with at least a 1.5-fold increase or decrease in transcription, respectively, were selected for detailed investigation. Several genes involved in morphogenesis or related to metabolism (e.g., glycolysis, ethanol and fatty acid biosynthesis) were down-regulated. Moreover, surfactin decreased the expression of ERG1, ERG3, ERG9, ERG10 and ERG11 involved in ergosterol synthesis, whereas genes associated with ribosome biogenesis and iron metabolism and drug transport-related genes were up-regulated. Our data demonstrate that surfactin significantly influences the physiology and gene transcription of C. albicans, and could contribute to the development of a novel innovative complementary therapy.

Characterization of subtilosin gene in wild type Bacillus spp. and possible physiological role

In a designed study to screen for antimicrobial exhibiting bacteria using molecular aspects, Bacillus species were considered to investigate antibiotic biosynthesis genes. 28 bacterial strains and 3 induced mutants were screened for the presence of subtilosin gene (sbo) and subtilosin through PCR and Mass spectrometry respectively. Sbo gene was detected in 16 out of 28 Bacillus strains. The results from gene sequences deliberated by multiple sequence alignments revealed high-level homology to the sequences of the sbo-alb gene locus of B. subtilis 168 and the other limited reported strains. Hence, this report provided additional strains to support the idea of subtilosin gene predominance amongst Bacillus strains isolated from environment and to find different species containing homologous genes, furthermore the utilization of its conserved region as a means of identifying Bacillus spp. that produce subtilosin. This is the first report to confirm the detection of subtilosin production from B. amyloliquefaciens.

Characterization of subtilosin gene in wild type Bacillus spp. and possible physiological role

In a designed study to screen for antimicrobial exhibiting bacteria using molecular aspects, Bacillus species were considered to investigate antibiotic biosynthesis genes. 28 bacterial strains and 3 induced mutants were screened for the presence of subtilosin gene (sbo) and subtilosin through PCR and Mass spectrometry respectively. Sbo gene was detected in 16 out of 28 Bacillus strains. The results from gene sequences deliberated by multiple sequence alignments revealed high-level homology to the sequences of the sbo-alb gene locus of B. subtilis 168 and the other limited reported strains. Hence, this report provided additional strains to support the idea of subtilosin gene predominance amongst Bacillus strains isolated from environment and to find different species containing homologous genes, furthermore the utilization of its conserved region as a means of identifying Bacillus spp. that produce subtilosin. This is the first report to confirm the detection of subtilosin production from B. amyloliquefaciens.

Bacteria Halotolerant from Karst Sinkholes as a Source of Biosurfactants and Bioemulsifiers

Halotolerant bacteria with biosurfactant (BS) and bioemulsifiers (BE) activity can coexist in Karstic sinkholes with marine influence. Two sinkholes in the Yucatan peninsula were selected to isolate bacteria with BE and BS activity stable in NaCl. The optimal time, the effect of nitrogen and carbon source in the medium, and the conditions (agitation, pH and salinity) for the production of BS and BE compounds in planktonic and sessile (stimulate the formation of biofilms in cell roller) culture were determined. Eighty strains showed the highest emulsification activity (EI24 ≥ 50%) and drop-collapse ≥ 4 mm. 87% of the strains are moderately halotolerant, and 21% bordered the limit of extreme halotolerance. Twenty-four strains maintained or improved their BS and BE activity under salinity conditions at 5% and 10%, being the most active genera Bacillus, Paenibacillus and Lysinibacillus, identified by sequencing of the 16S rRNA gene. The results show that the nitrogen source positively affects the BS and BE activity, regardless of the type of culture. The sessile culture markedly stimulated BS activity with significant differences. However, we did not find a greater influence on the culture conditions. The results suggest that halotolerant bacteria from sinkholes could be implemented in bioremediation and other biotechnological applications.

Purification and characterization of antibacterial surfactin isoforms produced by Bacillus velezensis SK

Bacillus velezensis SK having broad-spectrum antimicrobial activity has been isolated from soil. The efficient extraction of antimicrobial compounds produced in various mediums has been done using Diaion HP-20 resin. Further, characterization of an antimicrobial compound by TLC, FTIR, in-situ bioautography analysis revealed the presence of cyclic lipopeptides, which is then purified by the combination of silica gel, size exclusion, dual gradient, and RP-HPLC chromatography techniques. Growth kinetic studies showed that Bacillus velezensis SK produces a mixture of lipopeptides (1.33 gL^-1). The lipopeptide exhibits good pH (2-10) and temperature stability up to 80 °C. LC-ESI-MS analysis of partially purified lipopeptide identified variant of surfactin, further analysis of purified chromatographic fractions revealed the occurrence of most abundant C₁₅-surfactin homologues (m/z 1036.72 Da). The isolated surfactin exhibits good antimicrobial activity (1600 AU/ml) against drug-resistant food-born B. cereus and human pathogen Staphylococcus aureus. Hence, identified strain B. velezensis SK and its potent antibacterial surfactin lipopeptide could be used in various food and biomedical applications.

Bacillus subtilis extracellular polymeric substances conditioning layers inhibit Escherichia coli adhesion to silicon surfaces: A potential candidate for interfacial antifouling additives

Biofouling on material surfaces is a ubiquitous problem in a variety of fields. In aqueous environments, the process of biofouling initiates with the formation of a layer of macromolecules called the conditioning layer on the solid-liquid interface, followed by the adhesion and colonization of planktonic bacteria and the subsequent biofilm development and maturation. In this study, the extracellular polymeric substances (EPS) secreted by Bacillus subtilis were collected and used to prepare conditioning layers on inert surfaces. The morphologies and antifouling performances of the EPS conditioning layers were investigated. It was found that the initial adhesion of Escherichia coli was inhibited on the surfaces precoated with EPS conditioning layers. To further explore the underlying antifouling mechanisms of the EPS conditioning layers, the respective roles of two constituents of B. subtilis EPS (γ-polyglutamic acid and surfactin) were investigated. This study has provided the possibility of developing a novel interfacial antifouling additive with the advantages of easy preparation, nontoxicity, and environmental friendliness.

Fe Nanoparticles Enhanced Surfactin Production in Bacillus amyloliquefaciens

Surfactin, as one of the most powerful biosurfactants, can be widely applied in agriculture, food, and pharmaceutics. However, low biosynthesis efficiency is the major obstacle in its commercialization. Here, we used nanoparticles to increase the surfactin production in Bacillus amyloliquefaciens MT45 through enhancing the secretion (the key step of surfactin biosynthesis). The results showed that the surfactin titer increased from 4.93 to 7.15 g/L in the flask and from 5.94 to 9.18 g/L in a 7 L bioreactor by adding 5 g/L Fe nanoparticles. They were the highest titers in the reported wild-type strain. Our results indicated that Fe nanoparticles enhanced the expression of genes involved in the biosynthesis of surfactin. Moreover, Fe nanoparticles increased the permeability of cell membranes, resulting in a more efficient secretion of surfactin. This study provides an efficient strategy for increasing the biosynthesis of microbial metabolites and provides new insights into the nanoparticles' impacts on microbes.

Enhancement of atrazine biodegradation by marine isolate Bacillus velezensis MHNK1 in presence of surfactin lipopeptide

Atrazine is one of the widely used toxic herbicide and considered as serious environmental contaminant worldwide due to its long term use in crop production. In this study, the effect of surfactin lipopeptide produced by Bacillus velezensis MHNK1 on atrazine biodegradation was investigated. B. velezensis MHNK1 produced 0.83 ± 0.07 g/L of anionic biosurfactant that reduced surface tension from 72.12 ± 0.02 to 33.2 ± 0.61 mN/m and CMC was 40 mg/L with 85.21 ± 1.60% emulsification index. Further, biosurfactant was characterized as surfactin by TLC, HPLC, FTIR, ¹H and ¹³C NMR and LCMS-ESI. B. velezensis MHNK1 showed 87.10 ± 3.10% atrazine biodegradation within 5 days which was revealed by HPLC and MS analysis. Atrazine biodegradation using a combination of B. velezensis MHNK1 (2%) and surfactin (2 CMC) resulted in 100 ± 1.20% degradation within 4 days. Presence of atrazine degrading genes in B. velezensis MHNK1 was also confirmed by PCR. To the best of our knowledge, there are no previous reports available on atrazine degradation using B. velezensis strain and also in combination with surfactin. The results of this study reveal that strain B. velezensis MHNK1 and surfactin can be potential source of ecofriendly application for removal of atrazine from contaminated sites.

Effects of Different Cultivation Parameters on the Production of Surfactin Variants by a Bacillus subtilis Strain

Surfactins are lipopeptide-type biosurfactants produced mainly by Bacillus species, consisting of a peptide loop of seven amino acids and a hydrophobic fatty acid chain (C₁₂–C₁₆). These molecules have been proven to exhibit various biological activities; thus, their therapeutic and environmental applications are considered. Within the surfactin lipopeptide family, there is a wide spectrum of different homologues and isomers; to date, more than 30 variants have been described. Since the newest members of these lipopeptides were described recently, there is no information that is available on their characteristic features, e.g., the dependence of their production from different cultivation parameters. This study examined the effects of both the different carbon sources and various metal ions on the surfactin production of a selected B. subtilis strain. Among the applied carbon sources, fructose and xylose had the highest impacts on the ratio of the different variants, regarding both the peptide sequences and the lengths of the fatty acids. Furthermore, the application of metal ions Mn²⁺, Cu²⁺ and Ni²⁺ in the media completely changed the surfactin variant compositions of the fermenting broths leading to the appearance of methyl esterified surfactin forms, and resulted in the appearance of novel surfactin variants with fatty acid chains containing no more than 11 carbon atoms.

Culture Medium Development for Microbial-Derived Surfactants Production-An Overview

Surfactants are compounds that can reduce the surface tension between two different phases or the interfacial tension of the liquid between water and oil, possessing both hydrophilic and hydrophobic moieties. Biosurfactants have traits that have proven to be advantageous over synthetic surfactants, but these compounds do not compete economically with synthetic surfactants. Different alternatives increase the yield of biosurfactants; development of an economical production process and the usage of cheaper substrates during process have been employed. One of the solutions relies on the suitable formulation of a production medium by including alternative raw materials sourced from agro-wastes, hydrocarbons, or by-products of a process might help in boosting the biosurfactant production. Since the nutritional factors required will be different among microorganisms, the establishment of a suitable formulation for biosurfactant production will be challenging. The present review describes various nutrients and elements considered in the formulation of a production medium with an approach focusing on the macronutrient (carbon, nitrogen source, and C/N ratio), minerals, vitamins, metabolic regulators, and salinity levels which may aid in the study of biosurfactant production in the future.

Structural identification of lipopeptide biosurfactants produced by Bacillus subtilis strains grown on the media obtained from renewable natural resources

The aim of the study was to identify and characterize lipopeptide (LP) biosurfactants produced by two Bacillus subtilis strains (KP7 and I'-1a) grown on various media prepared from renewable natural resources: two different brewery wastewaters (BW#4 and BW#6), 2% beet molasses (M), apple peels extract (APE) supplemented with 0.25% of yeast extract (YE) or 0.25% peptone (P), and similarly supplemented carrot peels extract (CPE). In all used media both strains retained their individual LP production signature characterized by surfactin and iturin overproduction exhibited by KP7 and I'-1a strain, respectively. The production level and the structural diversity of synthesized LPs were dependent on the medium composition. In the CPE+YE medium it was higher than the yield obtained in Luria-Bertani (140.6 and 100.3 mg L^-1, respectively). Surfactins were produced by both strains as a mixture of four homologues (C13-C16) with the domination of variant C14. All other broths prepared from renewable resources strongly stimulated the iturin production by I'-1a strain with the exception of BW media. The highest iturin concentration (428.7 mg L^-1) obtained in the CPE+P culture of I'-1a strain was about seven-fold higher than in LB. In all cultures only iturin A was identified. Among four iturin homologues (C13-16) produced by I'-1a strain, the highest relative contents of C16 variant (70-80%) were calculated for samples obtained from APE+P and CPE+P media. The obtained data indicate that the waste composition has an influence on both the types and amounts of biosurfactants produced by studied B. subtilis strains.

Biocontrol activity of surfactin A purified from Bacillus NH-100 and NH-217 against rice bakanae disease

The potential of the Bacillus genus to antagonize phytopathogens is associated with the production of cyclic lipopeptides. Depending upon the type of lipopeptide, they may serve as biocontrol agents that are eco-friendly alternatives to chemical fertilizers. This study evaluates the biocontrol activity of surfactin-producing Bacillus (SPB) strains NH-100 and NH-217 and purified surfactin A from these strains against rice bakanae disease. Biologically active surfactin fractions were purified by HPLC, and surfactin A variants with chain lengths from C12 to C16 were confirmed by LCMS-ESI. In hemolytic assays, a positive correlation between surfactin A production and halo zone formation was observed. The purified surfactin A had strong antifungal activity against Fusarium oxysporum, F. moniliforme, F. solani, Trichoderma atroviride and T. reesei. Maximum fungal growth suppression (84%) was recorded at 2000 ppm against F. moniliforme. Surfactin A retained antifungal activity at different pH levels (5-9) and temperatures (20, 50 and 121 °C). Hydroponic and pot experiments were conducted to determine the biocontrol activity of SPB strains and the purified surfactin A from these strains on Super Basmati rice. Surfactin production in the rice rhizosphere was detected by LCMS-ESI at early growth stages in hydroponics experiments inoculated with SPB strains. However, the maximum yield was observed with a consortium of SPB strains (T4) and purified surfactin A (T5) treatments in the pot experiment. The outcomes of the present study revealed that surfactin A significantly reduced rice bakanae disease by up to 80%. These findings suggest that purified surfactin A could be an effective biocontrol agent against bakanae disease in rice and should be incorporated into strategies for disease management.

Genetic basis for hyper production of hyaluronic acid in natural and engineered microorganisms

Hyaluronic acid, or HA, is a rigid and linear biopolymer belonging to the class of the glycosaminoglycans, and composed of repeating units of the monosaccharides glucuronic acid and N-acetylglucosamine. HA has multiple important functions in the human body, due to its properties such as bio-compatibility, lubricity and hydrophilicity, it is widely applied in the biomedical, food, health and cosmetic fields. The growing interest in this molecule has motivated the discovery of new ways of obtaining it. Traditionally, HA has been extracted from rooster comb-like animal tissues. However, due to legislation laws HA is now being produced by bacterial fermentation using Streptococcus zooepidemicus, a natural producer of HA, despite it being a pathogenic microorganism. With the expansion of new genetic engineering technologies, the use of organisms that are non-natural producers of HA has also made it possible to obtain such a polymer. Most of the published reviews have focused on HA formulation and its effects on different body tissues, whereas very few of them describe the microbial basis of HA production. Therefore, for the first time this review has compiled the molecular and genetic bases for natural HA production in microorganisms together with the main strategies employed for heterologous production of HA.

Screening concepts, characterization and structural analysis of microbial-derived bioactive lipopeptides: a review

Lipopeptide biosurfactants are surface active biomolecules that are produced by a variety of microorganisms. Microbial lipopeptides have gained the interest of microbiologists, chemists and biochemists for their high biodiversity as well as efficient action, low toxicity and good biodegradability in comparison to synthetic counterparts. In this report, we review methods for the production, isolation and screening, purification and structural characterization of microbial lipopeptides. Several techniques are currently available for each step, and we describe the most commonly utilized and recently developed techniques in this review. Investigations on lipopeptide biosurfactants in natural products require efficient isolation techniques for the characterization and evaluation of chemical and biological properties. A combination of chromatographic and spectroscopic techniques offer opportunities for a better characterization of lipopeptide structures, which in turn can lead to the application of lipopeptides in food, pharmaceutical, cosmetics, agricultural and bioremediation industries.

Production and characterization of a new antibacterial peptide obtained from Aeribacillus pallidus SAT4

A novel thermophilic bacterial strain of the genus Aeribacillus was isolated from Thar Dessert Pakistan. This strain showed significant antibacterial activity against Micrococcus luteus, Staphylococcus aureus, and Pseudomonasaeruginosa. The strain coded as 'SAT4' resembled with Aeribacillus pallidus in the morphological, biochemical and molecular tests. The production of antibacterial metabolites by SAT4 was optimized. These active metabolites were precipitated by 50% ammonium sulphate and purified through sephadex G-75 gel permeation chromatography and reverse phase HPLC. The molecular weight of 37 kDa was examined by SDS-PAGE. The structural elucidation of the purified product was studied by FTIR, 1H and 13C NMR. The X-ray diffractions study showed that the crystals belonged to the primitive orthorhombic lattice (a = 12.137, b = 13.421, c = 14.097 Å) and 3D structure (proposed name: Aeritracin) was determined. This new peptide antibacterial molecule can get a position in pharmaceutical and biotechnological industrial research.

Water surface tension modulates the swarming mechanics of Bacillus subtilis

Many Bacillus subtilis strains swarm, often forming colonies with tendrils on agar medium. It is known that B. subtilis swarming requires flagella and a biosurfactant, surfactin. In this study, we find that water surface tension plays a role in swarming dynamics. B. subtilis colonies were found to contain water, and when a low amount of surfactin is produced, the water surface tension of the colony restricts expansion, causing bacterial density to rise. The increased density induces a quorum sensing response that leads to heightened production of surfactin, which then weakens water surface tension to allow colony expansion. When the barrier formed by water surface tension is breached at a specific location, a stream of bacteria swarms out of the colony to form a tendril. If a B. subtilis strain produces surfactin at levels that can substantially weaken the overall water surface tension of the colony, water floods the agar surface in a thin layer, within which bacteria swarm and migrate rapidly. This study sheds light on the role of water surface tension in regulating B. subtilis swarming, and provides insight into the mechanisms underlying swarming initiation and tendril formation.

Biosurfactant production by Bacillus subtilis using corn steep liquor as culture medium

In this work, biosurfactant production by Bacillus subtilis #573 was evaluated using corn steep liquor (CSL) as culture medium. The best results were obtained in a culture medium consisting of 10% (v/v) of CSL, with a biosurfactant production of about 1.3 g/l. To the best of our knowledge, this is the first report describing biosurfactant production by B. subtilis using CSL as culture medium. Subsequently, the effect of different metals (iron, manganese, and magnesium) on biosurfactant production was evaluated using the medium CSL 10%. It was found that for all the metals tested, the biosurfactant production was increased (up to 4.1, 4.4, and 3.5 g/l for iron, manganese, and magnesium, respectively). When the culture medium was supplemented with the optimum concentration of the three metals simultaneously, the biosurfactant production was increased up to 4.8 g/l. Furthermore, the biosurfactant exhibited a good performance in oil recovery assays when compared with chemical surfactants, which suggests its possible application in microbial enhanced oil recovery or bioremediation.

Hard surface biocontrol in hospitals using microbial-based cleaning products

BACKGROUND

Healthcare-Associated Infections (HAIs) are one of the most frequent complications occurring in healthcare facilities. Contaminated environmental surfaces provide an important potential source for transmission of many healthcare-associated pathogens, thus indicating the need for new and sustainable strategies.

AIM

This study aims to evaluate the effect of a novel cleaning procedure based on the mechanism of biocontrol, on the presence and survival of several microorganisms responsible for HAIs (i.e. coliforms, Staphyloccus aureus, Clostridium difficile, and Candida albicans) on hard surfaces in a hospital setting.

METHODS

The effect of microbial cleaning, containing spores of food grade Bacillus subtilis, Bacillus pumilus and Bacillus megaterium, in comparison with conventional cleaning protocols, was evaluated for 24 weeks in three independent hospitals (one in Belgium and two in Italy) and approximately 20000 microbial surface samples were collected.

RESULTS

Microbial cleaning, as part of the daily cleaning protocol, resulted in a reduction of HAI-related pathogens by 50 to 89%. This effect was achieved after 3-4 weeks and the reduction in the pathogen load was stable over time. Moreover, by using microbial or conventional cleaning alternatively, we found that this effect was directly related to the new procedure, as indicated by the raise in CFU/m2 when microbial cleaning was replaced by the conventional procedure. Although many questions remain regarding the actual mechanisms involved, this study demonstrates that microbial cleaning is a more effective and sustainable alternative to chemical cleaning and non-specific disinfection in healthcare facilities.

CONCLUSIONS

This study indicates microbial cleaning as an effective strategy in continuously lowering the number of HAI-related microorganisms on surfaces. The first indications on the actual level of HAIs in the trial hospitals monitored on a continuous basis are very promising, and may pave the way for a novel and cost-effective strategy to counteract or (bio)control healthcare-associated pathogens.

Rapid discrimination of bacteria by paper spray mass spectrometry

Paper spray mass spectrometry ambient ionization is utilized for rapid discrimination of bacteria without sample preparation. Bacterial colonies were smeared onto filter paper precut to a sharp point, then wetted with solvent and held at a high potential. Charged droplets released by field emission were sucked into the mass spectrometer inlet and mass spectra were recorded. Sixteen different species representing eight different genera from Gram-positive and Gram-negative bacteria were investigated. Phospholipids were the predominant species observed in the mass spectra in both the negative and positive ion modes. Multivariate data analysis based on principal component analysis, followed by linear discriminant analysis, allowed bacterial discrimination. The lipid information in the negative ion mass spectra proved useful for species level differentiation of the investigated Gram-positive bacteria. Gram-negative bacteria were differentiated at the species level by using a numerical data fusion strategy of positive and negative ion mass spectra.

The bacterial lipopeptide iturins induce Verticillium dahliae cell death by affecting fungal signalling pathways and mediate plant defence responses involved in pathogen-associated molecular pattern-triggered immunity

Verticillium wilt in cotton caused by Verticillium dahliae is one of the most serious plant diseases worldwide. Because no known fungicides or cotton cultivars provide sufficient protection against this pathogen, V. dahliae causes major crop yield losses. Here, an isolated cotton endophytic bacterium, designated Bacillus amyloliquefaciens 41B-1, exhibited greater than 50% biocontrol efficacy against V. dahliae in cotton plants under greenhouse conditions. Through high-performance liquid chromatography and mass analysis of the filtrate, we found that the antifungal compounds present in the strain 41B-1 culture filtrate were a series of isoforms of iturins. The purified iturins suppressed V. dahliae microsclerotial germination in the absence or presence of cotton. Treatment with the iturins induced reactive oxygen species bursts, Hog1 mitogen-activated protein kinase (MAPK) activation and defects in cell wall integrity. The oxidative stress response and high-osmolarity glycerol pathway contribute to iturins resistance in V. dahliae. In contrast, the Slt2 MAPK pathway may be involved in iturins sensitivity in this fungus. In addition to antagonism, iturins could induce plant defence responses as activators and mediate pathogen-associated molecular pattern-triggered immunity. These findings suggest that iturins may affect fungal signalling pathways and mediate plant defence responses against V. dahliae.

Sonorensin: an antimicrobial peptide, belonging to the heterocycloanthracin subfamily of bacteriocins, from a new marine isolate, Bacillus sonorensis MT93

Marine environments are the greatest fronts of biodiversity, representing a resource of unexploited or unknown microorganisms and new substances having potential applications. Among microbial products, antimicrobial peptides (AMPs) have received great attention recently due to their applications as food preservatives and therapeutic agents. A new marine soil isolate producing an AMP was identified as Bacillus sonorensis based on 16S rRNA gene sequence analysis. It produced an AMP that showed a broad spectrum of activity against both Gram-positive and Gram-negative bacteria. The peptide, named sonorensin, was purified to homogeneity using a combination of chromatographic techniques. The intact molecular mass of the purified peptide, 6,274 Da, as revealed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF), was in agreement with Tricine-SDS-PAGE analysis. A PCR array of primers was used to identify AMP structural genes, which allowed the successful amplification of the related genes from strain MT93. The putative open reading frame of sonorensin was amplified, cloned into the pET-32a(+) vector, expressed as a thioredoxin (Trx) fusion protein in Escherichia coli, and then purified. Sequence alignment analysis revealed that the bacteriocin being reported could belong to new subfamily of bacteriocins, heterocycloanthracin. The peptide indicated its potential as a biocontrol agent or food antimicrobial agent, due to its antimicrobial activity against bacteria such as Listeria monocytogenes and Staphylococcus aureus. This is the first report of the production, purification, and characterization of wild-type and recombinant bacteriocin by B. sonorensis and the first bacteriocin of the heterocycloanthracin subfamily to be characterized.

Bacillus amyloliquefaciens Q-426 as a potential biocontrol agent against Fusarium oxysporum f. sp. spinaciae

In recent years, Bacillus species have received considerable attention for the biological control of many fungal diseases. In this study, Bacillus amyloliquefaciens Q-426 was tested for its potential use against a variety of plant pathogens. Our screen for genes involved in the biosynthesis of antifungal agents revealed that the fen and bmy gene clusters are present in the Q-426 genome. Lipopeptides such as bacillomycin D, fengycin A, and fengycin B were purified from the bacterial culture broth and subsequently identified by ESI-mass spectrometry. The minimal inhibitory concentration of fengycin A against Fusarium oxysporum f. sp. spinaciae W.C. Snyder & H.N. Hansen O-27 was determined to be 31.25 μg ml(-1) . However, exposure of fungal cells to 50 μg ml(-1) of fengycin A did not allow permeation of fluorescein diacetate into the cytoplasm through the cell membrane. Moreover, leakage of intracellular inorganic cations, nucleic acid and protein were also not detected, indicating that the fungal cell membrane is not the primary target of action for fengycin A. Profound morphological changes were observed in the F. oxysporum strain and spore germination was completely inhibited, suggesting that 50 μg ml(-1) of fengycin A acts, at least, as a fungistatic agent.

Effects of critical medium components on the production of antifungal lipopeptides from Bacillus amyloliquefaciens Q-426 exhibiting excellent biosurfactant properties

In this study, influence of three critical parameters nitrogen sources, initial pH and metal ions was discussed in the production of antifungal lipopeptides from Bacillus amyloliquefaciens Q-426. The results revealed that lipopeptide biosynthesis might have relations with the population density of strain Q-426 and some special amino acids. Also, the alkali-resistant strain Q-426 could grow well in the presence of Fe(2+) ions below 0.8 M l(-1) and still maintain the competitive advantage below 0.2 M l(-1). Moreover, lipopeptides exhibited significant inhibitory activities against Curvularia lunata (Walk) Boed even at the extreme conditions of temperature, pH and salinity. Finally, biosurfactant properties of lipopeptides mixture were evaluated by use with totally six different methods including bacterial adhesion to hydrocarbons assay, lipase activity, hemolytic activity, emulsification activity, oil displacement test and surface tension measurement. The research suggested that B. amyloliquefaciens Q-426 may have great potential in agricultural and environmental fields.

Enhancement of lipopeptides production in a two-temperature-stage process under SSF conditions and its bioprocess in the fermenter

A two-temperature-stage process was developed for the production of lipopeptides under SSF conditions. The effects of various temperatures, ranging from 25 to 40 °C, on the bacterial growth during the growth stage and on the production of lipopeptides during the productive stage were investigated. The optimum temperatures were found to be 30 °C for the growth of the strain and 37 °C for the biosynthesis of lipopeptides. The two-stage fermentation temperatures should be 30 °C in the initial 24h and then 37 °C for the enhanced production of lipopeptides. The bioprocess results obtained in a 50 L fermenter verified the efficacy of this technique, which increased the yield of lipopeptides by 8.40% in flasks and by 13.11% in the fermenter, with a 4h decrease of fermentation time in the fermenter. The 1000-fold scale-up of fermentation in a fermenter was successfully achieved.

Removal of mercury by foam fractionation using surfactin, a biosurfactant

The separation of mercury ions from artificially contaminated water by the foam fractionation process using a biosurfactant (surfactin) and chemical surfactants (SDS and Tween-80) was investigated in this study. Parameters such as surfactant and mercury concentration, pH, foam volume, and digestion time were varied and their effects on the efficiency of mercury removal were investigated. The recovery efficiency of mercury ions was highly sensitive to the concentration of the surfactant. The highest mercury ion recovery by surfactin was obtained using a surfactin concentration of 10 × CMC, while recovery using SDS required < 10 × CMC and Tween-80 >10 × CMC. However, the enrichment of mercury ions in the foam was superior with surfactin, the mercury enrichment value corresponding to the highest metal recovery (10.4%) by surfactin being 1.53. Dilute solutions (2-mg L⁻¹ Hg²⁺) resulted in better separation (36.4%), while concentrated solutions (100 mg L⁻¹) enabled only a 2.3% recovery using surfactin. An increase in the digestion time of the metal solution with surfactin yielded better separation as compared with a freshly-prepared solution, and an increase in the airflow rate increased bubble production, resulting in higher metal recovery but low enrichment. Basic solutions yielded higher mercury separation as compared with acidic solutions due to the precipitation of surfactin under acidic conditions.

Microbial biosurfactants production, applications and future potential

Microorganisms synthesise a wide range of surface-active compounds (SAC), generally called biosurfactants. These compounds are mainly classified according to their molecular weight, physico-chemical properties and mode of action. The low-molecular-weight SACs or biosurfactants reduce the surface tension at the air/water interfaces and the interfacial tension at oil/water interfaces, whereas the high-molecular-weight SACs, also called bioemulsifiers, are more effective in stabilising oil-in-water emulsions. Biosurfactants are attracting much interest due to their potential advantages over their synthetic counterparts in many fields spanning environmental, food, biomedical, and other industrial applications. Their large-scale application and production, however, are currently limited by the high cost of production and by limited understanding of their interactions with cells and with the abiotic environment. In this paper, we review the current knowledge and the latest advances in biosurfactant applications and the biotechnological strategies being developed for improving production processes and future potential.

Surfactin: biosynthesis, genetics and potential applications

Even after forty years of its discovery by Arima et al, surfactin, a potent lipopeptide biosurfactant, still attracts attention and fancy of the applied microbiologists and biotechnologists worldwide, mainly due to its versatile bioactive properties and potential industrial implications. Starting from its first invented characteristic as an inhibitor of fibrin clot formation coupled with its significant ability to reduce surface tension of water, it has been credited with antifungal, antiviral, antitumor, insecticidal and antimycoplasma activities. These properties of therapeutic and commercial importance and its recent use as an enhanced oil recovery and a bioremediation agent make it a truly versatile biomolecule, the commercial potential of which could not be fully realized, particularly as a therapeutic agent, mainly because of its hemolytic property. This chapter thus addresses the issues related to the versatile nature of the most studied microbial surfactant, surfactin and its potential commercial and health-care applications.

Phylogeny in aid of the present and novel microbial lineages: diversity in Bacillus

Bacillus represents microbes of high economic, medical and biodefense importance. Bacillus strain identification based on 16S rRNA sequence analyses is invariably limited to species level. Secondly, certain discrepancies exist in the segregation of Bacillus subtilis strains. In the RDP/NCBI databases, out of a total of 2611 individual 16S rDNA sequences belonging to the 175 different species of the genus Bacillus, only 1586 have been identified up to species level. 16S rRNA sequences of Bacillus anthracis (153 strains), B. cereus (211 strains), B. thuringiensis (108 strains), B. subtilis (271 strains), B. licheniformis (131 strains), B. pumilus (83 strains), B. megaterium (47 strains), B. sphaericus (42 strains), B. clausii (39 strains) and B. halodurans (36 strains) were considered for generating species-specific framework and probes as tools for their rapid identification. Phylogenetic segregation of 1121, 16S rDNA sequences of 10 different Bacillus species in to 89 clusters enabled us to develop a phylogenetic frame work of 34 representative sequences. Using this phylogenetic framework, 305 out of 1025, 16S rDNA sequences presently classified as Bacillus sp. could be identified up to species level. This identification was supported by 20 to 30 nucleotides long signature sequences and in silico restriction enzyme analysis specific to the 10 Bacillus species. This integrated approach resulted in identifying around 30% of Bacillus sp. up to species level and revealed that B. subtilis strains can be segregated into two phylogenetically distinct groups, such that one of them may be renamed.