Interactive optimization of biosurfactant production by Paenibacillus alvei ARN63 isolated from an Iranian oil well

Production of rhamnolipid biosurfactants in solid-state fermentation: process optimization and characterization studies

BACKGROUND

Rhamnolipids are a group of the extracellular microbial surface-active molecules produced by certain Pseudomonas species with various environmental and industrial applications. The goal of the present research was to identify and optimize key process parameters for Pseudomonas aeruginosa PTCC 1074s synthesis of rhamnolipids utilizing soybean meal in solid state fermentation. A fractional factorial design was used to screen the key nutritional and environmental parameters to achieve the high rhamnolipid production. Response surface methodology was used to optimize the levels of four significant factors.

RESULTS

The characterization of biosurfactant by TLC, FT-IR and H-NMR showed the rhamnolipids presence. In the optimum conditions (temperature 34.5 °C, humidity 80%, inoculum size 1.4 mL, and glycerol 5%), the experimental value of rhamnolipid production was 19.68 g/kg dry substrate. The obtained rhamnolipid biosurfactant decreased water's surface tension from 71.8 ± 0.4 to 32.2 ± 0.2 mN/m with a critical micelle concentration of nearly 70 mg/L. Additionally, analysis of the emulsification activity revealed that the generated biosurfactant was stable throughout a broad pH, temperature, and NaCl concentration range.

CONCLUSIONS

The current study confirmed the considerable potential of agro-industrial residues in the production of rhamnolipid and enhanced the production yield by screening and optimizing the significant process parameters.

Anti-oxidative property of xylolipid produced by Lactococcus lactis LNH70 and its potential use as fruit juice preservative

In the present study, 20 lactic acid bacteria (LAB) were isolated from different fruit juices, milk, and milk products. Based on preliminary screening methods like emulsification index, oil displacement method, hemolysis, and reduction in surface tension, strain LNH70 was selected for further studies. Further, it was evaluated for preliminary probiotic characteristics, identified by 16 s rRNA sequencing as Lactococcus lactis, submitted to NCBI, and an accession number was obtained (MH174454). In addition, LNH70 was found to tolerate over wide range of temperatures (10-45 °C), pH (3-10), NaCl (up to 9%), bile (0.7%), and phenol (0.1%) concentrations. Further, optimization studies at flask level revealed that lactose as carbon source, peptone as organic nitrogen, and inorganic nitrogen (ammonium sulfate) enhanced biosurfactant production. Chemical composition of purified biosurfactant obtained from LNH70 was characterized by various physico-chemical analytical techniques and identified as xylolipid. Xylolipid biosurfactant exhibited anti-adhesion activity against food borne pathogens in in vitro conditions. Its anti-oxidative property by 1, 1-diphenyl-2-picrylhydrazyl (DPPH), 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS), and ferric reducing antioxidant power (FRAP) radical scavenging activity was found in range of 60.76 ± 0.5 to 83.50 ± 0.73%. Furthermore, xylolipid (0.05, 0.1, 0.3 mg/mL) when used for its potential as orange and pineapple juices preservation revealed miniature changes in the physico-chemical parameters evaluated in this study. However, the microbial population slightly lowered when xylolipid was used at 0.3 mg/mL after 5th day. Hence, this study supports the potential use of biosurfactant from L. lactis for its application as food preservative.

Formulation of a Culture Medium to Optimize the Production of Lipopeptide Biosurfactant by a New Isolate of Bacillus sp.: A Soil Heavy Metal Mitigation Approach

This research aimed to optimize a lipopeptide biosurfactant produced from Bacillus sp. SHA302 due to its high efficiency of heavy metal release in soil. The results demonstrated that the metal release capacity of the lipopeptide biosurfactant alone increased with increasing the biosurfactant concentration. Among treatments with different biosurfactant concentrations plus acid, the highest metal release rates of 53.8% ± 1.4 and 39.3% ± 1.7 for Zn and Pb, respectively, were observed in the critical micelle concentration (CMC) + HCl treatment. The results of a factorial experiment designed for optimizing biosurfactant production showed that among five inexpensive carbon sources and six mineral nitrogen sources, sugar beet molasses (1%) and ammonium chloride (0.1%) were the most efficient sources in lowering the surface tension (ST) of the culture media to 32.2 ± 0.76 mN/m. The second step of the experiment was a Plackett-Burman design with 11 factors and showed that the four factors of pH, ammonium chloride, magnesium sulfate, and molasses significantly affected (P < 0.05) the changes in ST and biosurfactant production. The third step of the experiment was done using the response surface methodology (RSM) with a central composite design. The results showed that a pH of 7.3, 1.5 g/l of ammonium chloride, 0.3 g/l of magnesium sulfate, and 10% of sugar beet molasses yielded values of 29.2 ± 0.71 mN/m and 5.74 ± 0.52 g/l for the two variables of ST and biosurfactant production, respectively, which reached their most optimal levels.

Production and Characterization of a Novel Biosurfactant Molecule from Bacillus safensis YKS2 and Assessment of Its Efficiencies in Wastewater Treatment by a Directed Metagenomic Approach

Biosurfactant is a biodegradation accelerator that improves bioavailability and facilitates degradation by microorganisms. The study was meant to produce a novel biosurfactant molecule from Bacillussafensis YKS2. An efficient biosurfactant-producing strain, namely, Bacillus safensis YKS2, was selected using hemolytic activity, drop collapsing test, oil spreading test and blue agar plate methods in four oil-degrading strains isolated from a soil sample. Biosurfactant production in the optimization of bacteria culture conditions by RSM is a statistical grouping technique that is analyzed using the AVOVA approach to surface tention. In addition, the study was characterized by UV spectrophotometer FT-IR, HR-SEM, and GC-MS analyses to explain its structural and chemical details. Wastewater treatment was monitored for pH, EC, turbidity, alkalinity, chemical oxygen demand (COD), biochemical oxygen demand (BOD) and dissolved oxygen (DO) in order to justify the efficacy of the biosurfactant during wastewater treatment. The results of the UV spectrophotometer showed absorption at 530 nm, and the FT-IR analyzed carboxylic acids, alcohol and phenols groups, whichthe GC-MS analysis indicated were lipopeptide purified by hexadecanoic andtetradecanoic processes, respectively. The results show that the wastewater removal efficiency of 70% wasachieved within 24 h. In comparison, metagenomics was conducted during the treatment process to identify changes in the microbial load and diversity, which essentially indicatethe biosurfactant performance of the wastewater treatment process. The microbial load in the treated biosurfactant wastewater (84,374 sequences) was greatly decreased compared to untreated wastewater (139,568 sequences). It was concluded that B. safensis YKS2, producing a glycolipid form of biosurfactant, has possible benefits in the remediation of wastewater, and can be used for large-scale processing inbiosurfactant industries.

Enhanced Oil Recovery by Potential Biosurfactant-Producing Halo-thermotolerant Bacteria Using Soil Washing and Sand-Packed Glass Column Techniques

Biosurfactants offer numerous advantages over the chemical surfactants, especially in energy and environment-related applications. Microbial enhanced oil recovery (MEOR) is a technique to recover oil from reservoirs by using microbes and their metabolites. In present study, total sixteen morphologically distinct bacterial strains isolated from different salty areas of the district Khairpur Mir's, Pakistan, were investigated for their MEOR potential. Screening assays for thermotolerance and halotolerance declared 7 out of 16 (43.75%) bacterial isolates as thermotolerant (capable of growing in the temperature range 60-70 °C) and halotolerant (tolerating NaCl concentrations up to 17%, w/v). Moreover, five of them were screened as biosurfactant producers. Among, the lowest surface tension reduction was achieved with biosurfactants produced by the strains KJ2MO (27.8 mN/m) and KJ2SK (29.3 mN/m). The biosurfactant activity was found stable at temperature (100-121 °C, 1 h) and pH (4-10). Moreover, maximum oil recovery was obtained with biosurfactant of bacterial strain KJ2MO (54.7%, 51.25%) followed by KJ2SK (44.7%, 40.5%), KJ1WB (37%, 35.5%) and KJ2MD (37.8%, 31.9%) by using either techniques, i.e., soil washing and sand-packed column, respectively. Moreover, the potent species were identified as Pseudomonas pseudoalcaligenes KJ1WB, Bacillus aerius KJ2MD, Bacillus licheniformis KJ2SK, and Bacillus subtilis KJ2MO using 16S rRNA ribo-typing. The investigated species were found to be promising biosurfactants producers having potential for enhanced oil recovery and could be used in other environmental applications like bioremediation.

Biosurfactant: A new frontier for greener technology and environmental sustainability

Petroleum hydrocarbons, oil, heavy metals pollution is becoming additional severe problem due to the growing call for crude oil and crude oil products related products in several fields of application. Such pollution have fascinated much considerations and attractions as it leads to ecological damages in both marines, aquatic and terrestrial ecosystems. Thus, different techniques including chemical surfactants and complex technologies have been proposed for their clean up from the environment, which in turn has detrimental effects on the environment. As of late, biosurfactant compounds have added much deliberation since they are considered as a reasonable option and eco-accommodating materials for remediation technology. The present society is confronting a few difficulties of usage, authorizing ecological protection and environmental change for the next generations. Biosurfactants hold the special property of minimizing and reducing the interfacial tension of liquids. Such features endure biosurfactants to afford a major part in emulsification, de-emulsification, biodegradability, foam formation, washing performance, surface activity, and detergent formulation, which have potential applications in the diverse industrial set-up. Conversations on cost-effective technologies, renewable materials, novel synthesis, downstream, upstream, emerging characterization techniques, molecular, and genetical engineering are substantial to produce biosurfactant of quality and quantity. Therefore, greater attention is being paid to biosurfactant production by identifying their environmental, and biotechnological applications. Be that as it may, the extravagant cost drew in with biosurfactants biotechnological synthesis and recovery can hamper their application in those areas. Notwithstanding these costs, biosurfactants can be used as these parts shows outstandingly high benefits that can at present beat the expenses incurred in the initial purification and downstream processes. Biosurfactant production by microorganisms is relatively considered one of the crucial know-how for improvement, growth, advancement, and environmental sustainability of the 21st century. There is a developing conversation around environmental safety and the significant role that biosurfactants will progressively play soon, for instance, the use of renewable by-products as substrates, potential reduction, re-use and recycling of waste and waste products. The review confers the usefulness of biosurfactants in the removal of environmental contaminants and, consequently, expanding environmental safety and drive towards greener technology.

Physicochemical characterization and optimization of glycolipid biosurfactant production by a native strain ofPseudomonas aeruginosaHAK01 and its performance evaluation for the MEOR process

In this study, a glycolipid type of biosurfactant (BS) was produced, its characteristics were evaluated and several flooding tests were conducted in a micromodel to investigate its potential for enhancing oil recovery. A rhamnolipid BS producer strain was identified as a bacterium belonging to the genus Pseudomonas aeruginosa. This BS showed good stability at temperatures of 40–121 °C, pH values of 3–10 and salinity up to 10% (w/v) NaCl which is important in Microbial Enhanced Oil Recovery (MEOR). The rhamnolipid decreased the surface tension of water from 72 to 28.1 mN m⁻¹ with a critical micelle concentration of 120 ppm. Thin layer chromatography, FTIR spectroscopy, ¹H-NMR and ¹³C-NMR spectroscopy revealed the glycolipid structure of the BS. Response surface methodology was applied to optimize BS production. Several micromodel flooding tests were conducted to study the capability of the produced rhamnolipid in enhanced oil recovery for the first time. An oil recovery factor of 43% was obtained at 120 ppm of BS solution whereas the recovery factor obtained for water flooding was 16%. Contact angle measurements showed that BS solutions altered the wettability of a glass surface from oil wet to a strongly water wet state. Also the results illustrated that all BS solutions were impressive in microbial enhanced oil recovery (MEOR) and using the produced BS a considerable amount of trapped oil can be extracted due to interfacial tension reduction, wettability alteration towards water wet conditions and improving the mobility ratio.

In this study, a glycolipid type of biosurfactant (BS) was produced, its characteristics were evaluated and several flooding tests were conducted in a micromodel to investigate its potential for enhancing oil recovery.

Isolation and characterization of biosurfactant producing and oil degrading Bacillus subtilis MG495086 from formation water of Assam oil reservoir and its suitability for enhanced oil recovery

The strains isolated from the formation water were characterized and screened considering their crude oil degradation capability and biosurfactant production ability. The growth kinetics study of isolated Bacillus subtilis MG495086 was carried out by varying growth parameters i.e. carbon source, temperature, pH and salinity. The biosurfactant production was optimized adopting RSM-CCD considering carbon source (1-5%), pH (3-11) and temperature (25-65 °C) as matrix parameters. The optimum biosurfactant production (6.3 ± 0.1 g/L) and the minimum surface tension 29.85 mN/m were obtained after 96 h of incubation under optimal conditions i.e. 3.8% (v/v) of light-paraffin oil as sole carbon source at 62.4 °C and pH 7.7 with the maximum oil degradation capability of 91.3 ± 5%. Critical micelle concentration value of crude biosurfactant was found to be 40 mg/L with high emulsification activity of 72.45 ± 0.85%. The produced biosurfactant was identified as lipopeptide (Surfactin) and characterized using various analytical techniques to establish its suitability for microbial enhanced oil recovery.

Enhancement of Paenibacillus sp. D9 Lipopeptide Biosurfactant Production Through the Optimization of Medium Composition and Its Application for Biodegradation of Hydrophobic Pollutants

Interests in biosurfactant in industrial and environmental applications have increased considerably in recent years, owing to their potential benefits over synthetic counterparts. The present study aimed at analyzing the stability and oil removal efficiency of a new lipopeptide biosurfactant produced by Paenibacillus sp. D9 and its feasibility of its use in biotechnological applications. Paenibacillus sp. D9 was evaluated for optimal growth conditions and improved production yield of lipopeptide biosurfactant with variations in different substrate parameters such as carbon (C), nitrogen (N), C:N: ratio, metal supplements, pH, and temperature. Enhanced biosurfactant production was observed when using diesel fuel and ammonium sulfate as carbon and nitrogen source respectively. The maximum biosurfactant yield of 4.11 g/L by Paenibacillus sp. D9 occurred at a C/N ratio of 3:1, at pH 7.0, 30 °C, 4.0 mM MgSO₄, and 1.5% inoculum size. The D9 biosurfactant was found to retain surface-active properties under the extreme conditions such as high thermal, acidic, alkaline, and salt concentration. The ability to emulsify further emphasizes its potential usage in biotechnological application. Additionally, the lipopeptide biosurfactant exhibited good performance in the degradation of highly toxic substances when compared with chemical surfactant, which proposes its probable application in biodegradation, microbial-enhanced oil recovery or bioremediation. Furthermore, the biosurfactants were effective in a test to stimulate the solubilization of hydrophobic pollutants in both liquid environments removing 49.1 to 65.1% diesel fuel including hydrophobic pollutants. The study highlights the usefulness of optimization of culture parameters and their effects on biosurfactant production, high stability, improved desorption, and solubilization of hydrophobic pollutants.

Bacterial polyextremotolerant bioemulsifiers from arid soils improve water retention capacity and humidity uptake in sandy soil

Background

Water stress is a critical issue for plant growth in arid sandy soils. Here, we aimed to select bacteria producing polyextremotolerant surface-active compounds capable of improving water retention and humidity uptake in sandy soils.

Results

From Tunisian desert and saline systems, we selected eleven isolates able to highly emulsify different organic solvents. The bioemulsifying activities were stable with 30% NaCl, at 4 and 120 °C and in a pH range 4–12. Applications to a sandy soil of the partially purified surface-active compounds improved soil water retention up to 314.3% compared to untreated soil. Similarly, after 36 h of incubation, the humidity uptake rate of treated sandy soil was up to 607.7% higher than untreated controls.

Conclusions

Overall, results revealed that polyextremotolerant bioemulsifiers of bacteria from arid and desert soils represent potential sources to develop new natural soil-wetting agents for improving water retention in arid soils.

Electronic supplementary material

The online version of this article (10.1186/s12934-018-0934-7) contains supplementary material, which is available to authorized users.

The yeast-like fungus Aureobasidium thailandense LB01 produces a new biosurfactant using olive oil mill wastewater as an inducer

In this study, the biosurfactant production by an Aureobasidium thailandense LB01 was reported for the first time. Different agro-industrial by-products (corn steep liquor, sugarcane molasses, and olive oil mill wastewater) were evaluated as alternative low-cost substrates. The composition of the culture medium was optimized through response surface methodology. The highest biosurfactant production (139±16mg/L) was achieved using a culture medium containing yeast extract (2g/L); olive oil mill wastewater (1.5%, w/w); glucose (6g/L) and KH₂PO₄ (1g/L) after 48h of fermentation. The partially purified biosurfactant exhibited a critical micelle concentration of 550mg/L, reducing the surface tension of water up to 31.2mN/m. Its molecular structure was found to be similar to a lauric acid ester. The biosurfactant exhibited a better performance than the chemical surfactant sodium dodecyl sulfate (SDS) in oil dispersion assays, thus suggesting its potential application in bioremediation.

Response Surface Methodology for Optimizing the Production of Biosurfactant by Candida tropicalis on Industrial Waste Substrates

Biosurfactant production optimization by Candida tropicalis UCP0996 was studied combining central composite rotational design (CCRD) and response surface methodology (RSM). The factors selected for optimization of the culture conditions were sugarcane molasses, corn steep liquor, waste frying oil concentrations and inoculum size. The response variables were surface tension and biosurfactant yield. All factors studied were important within the ranges investigated. The two empirical forecast models developed through RSM were found to be adequate for describing biosurfactant production with regard to surface tension (R² = 0.99833) and biosurfactant yield (R² = 0.98927) and a very strong, negative, linear correlation was found between the two response variables studied (r = −0.95). The maximum reduction in surface tension and the highest biosurfactant yield were 29.98 mNm⁻¹ and 4.19 gL⁻¹, respectively, which were simultaneously obtained under the optimum conditions of 2.5% waste frying oil, 2.5%, corn steep liquor, 2.5% molasses, and 2% inoculum size. To validate the efficiency of the statistically optimized variables, biosurfactant production was also carried out in 2 and 50 L bioreactors, with yields of 5.87 and 7.36 gL⁻¹, respectively. Finally, the biosurfactant was applied in motor oil dispersion, reaching up to 75% dispersion. Results demonstrated that the CCRD was suitable for identifying the optimum production conditions and that the new biosurfactant is a promising dispersant for application in the oil industry.

Rhamnolipids Produced by Indigenous Acinetobacter junii from Petroleum Reservoir and its Potential in Enhanced Oil Recovery

Biosurfactant producers are crucial for incremental oil production in microbial enhanced oil recovery (MEOR) processes. The isolation of biosurfactant-producing bacteria from oil reservoirs is important because they are considered suitable for the extreme conditions of the reservoir. In this work, a novel biosurfactant-producing strain Acinetobacter junii BD was isolated from a reservoir to reduce surface tension and emulsify crude oil. The biosurfactants produced by the strain were purified and then identified via electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR-MS). The biosurfactants generated by the strain were concluded to be rhamnolipids, the dominant rhamnolipids were C26H48O9, C28H52O9, and C32H58O13. The optimal carbon source and nitrogen source for biomass and biosurfactant production were NaNO3 and soybean oil. The results showed that the content of acid components increased with the progress of crude oil biodegradation. A glass micromodel test demonstrated that the strain significantly increased oil recovery through interfacial tension reduction, wettability alteration and the mobility of microorganisms. In summary, the findings of this study indicate that the newly developed BD strain and its metabolites have great potential in MEOR.

Preliminary characterization of biosurfactant produced by a PAH-degrading Paenibacillus sp. under thermophilic conditions

The capacities of a biosurfactant producing and polycyclic aromatic hydrocarbon (PAH) utilizing bacterium, namely, strain 1C, isolated from an Algerian contaminated soil, were investigated. Strain 1C belonged to the Paenibacillus genus and was closely related to the specie Paenibacillus popilliae, with 16S rRNA gene sequence similarity of 98.4 %. It was able to produce biosurfactant using olive oil as substrate. The biosurfactant production was shown by surface tension (32.6 mN/m) after 24 h of incubation at 45 °C and 150 rpm. The biosurfactant(s) retained its properties during exposure to elevated temperatures (70 °C), relatively high salinity (20 % NaCl), and a wide range of pH values (2-10). The infrared spectroscopy (FTIR) revealed that its chemical structure belonged to lipopeptide class. The critical micelle concentration (CMC) of this biosurfactant was about 0.5 g/l with 29.4 mN/m. In addition, the surface active compound(s) produced by strain 1C enhanced PAH solubility and showed a significant antimicrobial activity against pathogens. In addition to its biosurfactant production, strain 1C was shown to be able to utilize PAHs as the sole carbon and energy sources. Strain 1C as hydrocarbonoclastic bacteria and its interesting surface active agent may be used for cleaning the environments polluted with polyaromatic hydrocarbons.

Evaluation of bacterial diversity recovered from petroleum samples using different physical matrices

Unraveling the microbial diversity and its complexity in petroleum reservoir environments has been a challenge throughout the years. Despite the techniques developed in order to improve methodologies involving DNA extraction from crude oil, microbial enrichments using different culture conditions can be applied as a way to increase the recovery of DNA from environments with low cellular density for further microbiological analyses. This work aimed at the evaluation of different matrices (arenite, shale and polyurethane foam) as support materials for microbial growth and biofilm formation in enrichments using a biodegraded petroleum sample as inoculum in sulfate reducing condition. Subsequent microbial diversity characterization was carried out using Scanning Electronic Microscopy (SEM), Denaturing Gradient Gel Electrophoresis (DGGE) and 16S rRNA gene libraries in order to compare the microbial biomass yield, DNA recovery efficiency and diversity among the enrichments. The DNA from microbial communities in petroleum enrichments was purified according to a protocol established in this work and used for 16S rRNA amplification with bacterial generic primers. The PCR products were cloned, and positive clones were screened by Amplified Ribosomal DNA Restriction Analysis (ARDRA). Sequencing and phylogenetic analyses revealed that the bacterial community was mostly represented by members of the genera Petrotoga, Bacillus, Pseudomonas, Geobacillus and Rahnella. The use of different support materials in the enrichments yielded an increase in microbial biomass and biofilm formation, indicating that these materials may be employed for efficient biomass recovery from petroleum reservoir samples. Nonetheless, the most diverse microbiota were recovered from the biodegraded petroleum sample using polyurethane foam cubes as support material.

Antifungal activity of chitinase obtained from Paenibacillus ehimensis MA2012 against conidial of Collectotrichum gloeosporioides in vitro

To investigate the expression patterns of chitinase on SDS-PAGE gel, Paenibacillus ehimensis MA2012 was incubated in gelatin-chitin medium (GCM) at 30 °C for 7 days. Six major bands (Ch3, Ch4, Ch5, Ch6, Ch7, and Ch8) of chitinase isozymes in GC medium appeared on SDS-PAGE gel during the incubation period. Chitinase activity staining of P. ehimensis MA2012 was detected on 2-DE with different pI values (4-11). After DEAE-Sephadex chromatography, eight bands (Ch1 to Ch8) of chitinase isozymes were stained strongly with Calcofluor white M2R at fraction 45. After Sephadex G-75 gel filtration, six bands (Ch3 to Ch8) of chitinase isozymes were stained with Calcofluor white M2R at fractions of 11-12. The specific activity of the purified chitinase was 3.8 units mg(-1) protein with a purification factor of 0.27. Inhibition rate of the conidial germination of Colletotrichum gloeosporioides was 87% in partial purified chitinase treatment compared with control.

Effect of Biostimulation Using Sewage Sludge, Soybean Meal, and Wheat Straw on Oil Degradation and Bacterial Community Composition in a Contaminated Desert Soil

Waste materials have a strong potential in the bioremediation of oil-contaminated sites, because of their richness in nutrients and their economical feasibility. We used sewage sludge, soybean meal, and wheat straw to biostimulate oil degradation in a heavily contaminated desert soil. While oil degradation was assessed by following the produced CO₂ and by using gas chromatography–mass spectrometry (GC–MS), shifts in bacterial community composition were monitored using illumina MiSeq. The addition of sewage sludge and wheat straw to the desert soil stimulated the respiration activities to reach 3.2–3.4 times higher than in the untreated soil, whereas the addition of soybean meal resulted in an insignificant change in the produced CO₂, given the high respiration activities of the soybean meal alone. GC–MS analysis revealed that the addition of sewage sludge and wheat straw resulted in 1.7–1.8 fold increase in the degraded C₁₄ to C₃₀ alkanes, compared to only 1.3 fold increase in the case of soybean meal addition. The degradation of ≥90% of the C₁₄ to C₃₀ alkanes was measured in the soils treated with sewage sludge and wheat straw. MiSeq sequencing revealed that the majority (76.5–86.4% of total sequences) of acquired sequences from the untreated soil belonged to Alphaproteobacteria, Gammaproteobacteria, and Firmicutes. Multivariate analysis of operational taxonomic units placed the bacterial communities of the soils after the treatments in separate clusters (ANOSIM R = 0.66, P = 0.0001). The most remarkable shift in bacterial communities was in the wheat straw treatment, where 95–98% of the total sequences were affiliated to Bacilli. We conclude that sewage sludge and wheat straw are useful biostimulating agents for the cleanup of oil-contaminated desert soils.

Novel bioemulsifier produced by a Paenibacillus strain isolated from crude oil

BACKGROUND

Surface active compounds produced by microorganisms are attracting a pronounced interest due to their potential advantages over their synthetic counterparts, and to the fact that they could replace some of the synthetics in many environmental and industrial applications.

RESULTS

Bioemulsifier production by a Paenibacillus sp. strain isolated from crude oil was studied. The bioemulsifier was produced using sucrose with and without adding hydrocarbons (paraffin or crude oil) under aerobic and anaerobic conditions at 40°C. It formed stable emulsions with several hydrocarbons and its emulsifying ability was not affected by exposure to high salinities (up to 300 g/l), high temperatures (100°C-121°C) or a wide range of pH values (2-13). In addition, it presented low toxicity and high biodegradability when compared with chemical surfactants. A preliminary chemical characterization by Fourier Transform Infrared Spectroscopy (FT-IR), proton and carbon nuclear magnetic resonance (1H NMR and 13C CP-MAS NMR) and size exclusion chromatography indicated that the bioemulsifier is a low molecular weight oligosaccharide-lipid complex.

CONCLUSION

The production of a low molecular weight bioemulsifier by a novel Paenibacillus strain isolated from crude oil was reported. To the best of our knowledge, bioemulsifier production by Paenibacillus strains has not been previously reported. The features of this novel bioemulsifier make it an interesting biotechnological product for many environmental and industrial applications. Graphical Abstract Novel bioemulsifier from Paenibacillus sp.

Isolation and characterization of an antimicrobial lipopeptide produced by Paenibacillus ehimensis MA2012

In this study, a novel lipopeptide antibiotic was isolated from the culture supernatant of Paenibacillus ehimensis strain MA2012. After analyses by mass spectrometry (MS), nuclear magnetic resonance (NMR), and high resolution mass spectrometry (HR-MS/MS) the compound was identified to be polypeptin C consisting of 3-hydroxy-4-methyl-hexanoic acid moiety and nine amino acids as peptide body. It has the same molecular mass (1115 Da) with that of polypeptin A and B but the amino acid positions differ. A relatively low concentration (125 ppm) of polypeptin C lowered the surface tension of water from 72.2 to 36.4 mN/m. It showed antimicrobial activity against several plant pathogenic bacteria and fungi. When the polypeptin C was applied to the ripe pepper fruits previously inoculated with conidia of Colletotrichum gloeosporioides, the hyphal growth on the fruit was significantly suppressed. Moreover, the hyphal morphology of C. gloeosporioides was greatly affected by the purified compound. All these data suggest the great potential of P. ehimensis MA2012 to control plant fungal and bacterial diseases.

Diversity of bacterial communities along a petroleum contamination gradient in desert soils

Microbial communities in oil-polluted desert soils have been rarely studied compared to their counterparts from freshwater and marine environments. We investigated bacterial diversity and changes therein in five desert soils exposed to different levels of oil pollution. Automated rRNA intergenic spacer (ARISA) analysis profiles showed that the bacterial communities of the five soils were profoundly different (analysis of similarities (ANOSIM), R = 0.45, P < 0.0001) and shared less than 20 % of their operational taxonomic units (OTUs). OTU richness was relatively higher in the soils with the higher oil pollution levels. Multivariate analyses of ARISA profiles revealed that the microbial communities in the S soil, which contains the highest level of contamination, were different from the other soils and formed a completely separate cluster. A total of 16,657 ribosomal sequences were obtained, with 42-89 % of these sequences belonging to the phylum Proteobacteria. While sequences belonging to Betaproteobacteria, Gammaproteobacteria, Bacilli, and Actinobacteria were encountered in all soils, sequences belonging to anaerobic bacteria from the classes Deltaproteobacteria, Clostridia, and Anaerolineae were only detected in the S soil. Sequences belonging to the genus Terriglobus of the class Acidobacteria were only detected in the B3 soil with the lowest level of contamination. Redundancy analysis (RDA) showed that oil contamination level was the most determinant factor that explained variations in the microbial communities. We conclude that the exposure to different levels of oil contamination exerts a strong selective pressure on bacterial communities and that desert soils are rich in aerobic and anaerobic bacteria that could potentially contribute to the degradation of hydrocarbons.

Production and characterization of rhamnolipids produced by Serratia rubidaea SNAU02 under solid-state fermentation and its application as biocontrol agent

The present study aimed at exploring mahua (Madhuca indica) oil cake as a novel substrate for the production of biosurfactant by Serratia rubidaea SNAU02 under solid-state fermentation (SSF). Response surface methodology showed followings as the optimal conditions for the production of biosurfactant: mahua oil cake 7.48 g, 2.5 ml inoculum size (1×10(8) cells/ml), and pH 7.22 and 31 °C temperature. The characterization of the biosurfactant by TLC, FT-IR and GC-MS revealed the presence of rhamnolipid. The presence of rhamnosyl transferase gene responsible for biosynthesis of rhamnolipid was identified. The strain SNAU02 exhibited antifungal activity and demonstrated no toxicity against the seeds of Brassica oleracea and Artemia salina employed as a bio-indicator. The present findings indicated the potential of mahua oil cake as suitable substrate for the production of rhamnolipids in SSF by S. rubidaea SNAU02 and application potential of the biosurfactant produced as biocontrol agent against plant pathogens.

Microbial diversity, community composition and metabolic potential in hydrocarbon contaminated oily sludge: prospects for in situ bioremediation

Microbial community composition and metabolic potential have been explored in petroleum-hydrocarbon-contaminated sludge of an oil storage facility. Culture-independent clone library-based 16S rRNA gene analyses revealed that the bacterial community within the sludge was dominated by the members of β-Proteobacteria (35%), followed by Firmicutes (13%), δ-Proteobacteria (11%), Bacteroidetes (10%), Acidobacteria (6%), α-Proteobacteria (3%), Lentisphaerae (2%), Spirochaetes (2%), and unclassified bacteria (5%), whereas the archaeal community was composed of Thermoprotei (54%), Methanocellales (33%), Methanosarcinales/Methanosaeta (8%) and Methanoculleus (1%) members. Methyl coenzyme M reductase A (mcrA) gene (a functional biomarker) analyses also revealed predominance of hydrogenotrophic, methanogenic Archaea (Methanocellales, Methanobacteriales and Methanoculleus members) over acetoclastic methanogens (Methanosarcinales members). In order to explore the cultivable bacterial population, a total of 28 resident strains were identified and characterized in terms of their physiological and metabolic capabilities. Most of these could be taxonomically affiliated to the members of the genera Bacillus, Paenibacillus, Micrococcus, Brachybacterium, Aerococcus, and Zimmermannella, while two strains were identified as Pseudomonas and Pseudoxanthomonas. Metabolic profiling exhibited that majority of these isolates were capable of growing in presence of a variety of petroleum hydrocarbons as sole source of carbon, tolerating different heavy metals at higher concentrations (≥1 mM) and producing biosurfactant during growth. Many strains could grow under a wide range of pH, temperature, or salinity as well as under anaerobic conditions in the presence of different electron acceptors and donors in the growth medium. Correlation between the isolates and their metabolic properties was estimated by the unweighted pair group method with arithmetic mean (UPGMA) analysis. Overall observation indicated the presence of diverse groups of microorganisms including hydrocarbonoclastic, nitrate reducing, sulphate reducing, fermentative, syntrophic, methanogenic and methane-oxidizing bacteria and Archaea within the sludge community, which can be exploited for in situ bioremediation of the oily sludge.

The S-layer homology domain-containing protein SlhA from Paenibacillus alvei CCM 2051(T) is important for swarming and biofilm formation

Background

Swarming and biofilm formation have been studied for a variety of bacteria. While this is well investigated for Gram-negative bacteria, less is known about Gram-positive bacteria, including Paenibacillus alvei, a secondary invader of diseased honeybee colonies infected with Melissococcuspluton, the causative agent of European foulbrood (EFB).

Methodology

Paenibacillus alvei CCM 2051^T is a Gram-positive bacterium which was recently shown to employ S-layer homology (SLH) domains as cell wall targeting modules to display proteins on its cell surface. This study deals with the newly identified 1335-amino acid protein SlhA from P. alvei which carries at the C‑terminus three consecutive SLH-motifs containing the predicted binding sequences SRGE, VRQD, and LRGD instead of the common TRAE motif. Based on the proof of cell surface location of SlhA by fluorescence microscopy using a SlhA-GFP chimera, the binding mechanism was investigated in an in vitro assay. To unravel a putative function of the SlhA protein, a knockout mutant was constructed. Experimental data indicated that one SLH domain is sufficient for anchoring of SlhA to the cell surface, and the SLH domains of SlhA recognize both the peptidoglycan and the secondary cell wall polymer in vitro. This is in agreement with previous data from the S-layer protein SpaA, pinpointing a wider utilization of that mechanism for cell surface display of proteins in P. alvei. Compared to the wild-type bacterium ΔslhA revealed changed colony morphology, loss of swarming motility and impaired biofilm formation. The phenotype was similar to that of the flagella knockout Δhag, possibly due to reduced EPS production influencing the functionality of the flagella of ΔslhA.

Conclusion

This study demonstrates the involvement of the SLH domain-containing protein SlhA in swarming and biofilm formation of P. alvei CCM 2051^T.

Detection of secreted antimicrobial peptides isolated from cell-free culture supernatant of Paenibacillus alvei AN5

An antimicrobial substance produced by the Paenibacillus alvei strain AN5 was detected in fermentation broth. Subsequently, cell-free culture supernatant (CFCS) was obtained by medium centrifugation and filtration, and its antimicrobial activity was tested. This showed a broad inhibitory spectrum against both Gram-positive and -negative bacterial strains. The CFCS was then purified and subjected to SDS-PAGE and infrared spectroscopy, which indicated the proteinaceous nature of the antimicrobial compound. Some de novo sequencing using an automatic Q-TOF premier system determined the amino acid sequence of the purified antimicrobial peptide as Y-S-K-S-L-P-L-S-V-L-N-P (1,316 Da). The novel peptide was designated as peptide AN5-1. Its mode of action was bactericidal, inducing cell lysis in E. coli ATCC 29522 and S. aureus, and non-cell lysis in both S. marcescens and B. cereus ATCC 14579. Peptide AN5-1 displayed stability at a wide range of pH values (2–12) and remained active after exposure to high temperatures (100 °C). It also maintained its antimicrobial activity after incubation with chemicals such as SDS, urea and EDTA.

Isolation and characterization of heavy-metal-mobilizing bacteria from contaminated soils and their potential in promoting Pb, Cu, and Cd accumulation by Coprinus comatus

The enhanced effect of heavy-metal-mobilizing bacteria on the uptake of Pb, Cu, and Cd by Coprinus comatus from Pb-, Cu-, and Cd-multicontaminated soil was assessed in this study. Thirteen strains, tolerating 800 mg·L–1 Pb, 200 mg·L–1 Cu, and 200 mg·L–1 Cd simultaneously were selected for heavy-metal-solubilizing experiments in soil. The mobilization of heavy metals depended on the characteristics of bacteria and heavy metals. Correlation analysis demonstrated that for Pb solubilization, the acid-producing ability was the most significant factor, while for Cu and Cd, siderophores played a leading role in this process. Four strains, based on their excellent ability to solubilize heavy metal in soil, were applied in pot experiments. The results showed that all strains can promote the growth of C. comatus and meanwhile help mushroom accumulate more heavy metals (Pb, Cd, and Cu). The maximum uptake for total Pb and Cu by C. comatus was observed in inoculations with Bacillus sp. strain JSG1 (2.02- and 2.13-fold, respectively, compared with uninoculated soil), while for Cd, it was recorded in Bacillus sp. strain PB2 treated soil (2.03-fold). Therefore, this work suggests that the mushroom–bacteria interaction can be developed into a novel bioremediation strategy.