Isolation,characterization, and antifungal application of a biosurfactant produced by Enterobacter sp. MS16

Isolate MS16 obtained from diesel contaminated soil, identified as Enterobacter sp. using 16S rRNA gene analysis produced biosurfactant when grown on unconventional substrates like groundnut oil cake, sunflower oil, and molasses. Of these carbon substrates used, sunflower oil cake showed highest biosurfactant production (1.5 g/L) and reduction in surface tension (68%). The biosurfactant produced by MS16 efficiently emulsified various hydrocarbons. The carbohydrates and fatty acids of the biosurfactants were studied using TLC, FTIR, NMR, and GC‐MS. The carbohydrate composition as determined by GC‐MS of their alditol acetate derivatives showed the predominance of glucose, galactose and arabinose, and hydroxyl fatty acids of chain length of C₁₆ and C₁₈ on the basis of FAMEs analysis. Biosurfactant showed antifungal activity and inhibited the fungal spore germination. Practical applications : Enterobacter sp., MS16 produces a biosurfactant composed of carbohydrates and fatty acids which exhibits excellent surface active properties. Use of industrial wastes for biosurfactant production is economical and facilitates the industrial production of this biosurfactant which has potential antifungal activity.     

Sunflower Acid Oil-Based Production of Rhamnolipid Using Pseudomonas aeruginosa and Its Application in Liquid Detergents

Utilization of industrial waste as substrates for the rhamnolipid synthesis by Pseudomonas aeruginosa is a worthy alternative for conventionally used vegetable oils and fatty acids to reduce the production cost of rhamnolipid. Sunflower acid oil (SAO), a by-product of the oil industry, contains 70% 18:0 fatty acid, with oleic acid as a major component. In this scope, production and analysis of rhamnolipid was successfully demonstrated using SAO as a new substrate. Pseudomonas aeruginosa produced rhamnolipid (a glycolipid biosurfactant) at a maximum concentration of 4.9 g L⁻¹ with 60 g L⁻¹ of SAO in the medium. Structural properties of rhamnolipid biosurfactant are confirmed using thin layer chromatography (TLC), high performance liquid chromatography (HPLC), and fourier transformed infrared spectroscopy (FTIR) analysis. Further surface-active properties of the crude rhamnolipid were evaluated by measuring surface tension and emulsification properties. The synthesized rhamnolipid reduced the surface tension of water to 30.12 mN m⁻¹ and interfacial tension (against heptane) to 0.52 mN m⁻¹. Moreover, rhamnolipid shows the highest emulsification index (above 80%) for vegetable oils. This study confirms the use of SAO as a potential substrate for rhamnolipid production. The synthesized rhamnolipid was incorporated in liquid detergent formulation along with alpha olefin sulfonate (AOS) and sodium lauryl ether sulfate (SLES). The performance properties including foaming and cleaning efficiency of liquid detergent were compared.     

Deacylation of Calcium-Dependent Antibiotics from Streptomyces violaceoruber in Co-culture with Streptomyces sp. MG7-G1

When Streptomyces violaceoruber grows together with Streptomyces sp. MG7-G1, it reacts with strongly induced droplet production on its aerial mycelium. Initially the metabolite profile of droplets from S. violaceoruber in co-culture with Streptomyces sp. MG7-G1 was compared to samples from S. violaceoruber in single-culture by using high-performance liquid chromatography-mass spectrometry (HPLC-MS). Then, the exudate from agar plates of co-cultures and single cultures (after freezing and thawing) was also analysed. Several compounds were only observed when S. violaceoruber was grown in co-culture. Based on their high-resolution ESI mass spectra and their comparable retention times to the calcium-dependent antibiotics (CDAs) produced by S. violaceoruber, the new compounds were suspected to be deacylated calcium-dependent antibiotics (daCDAs), lacking the 2,3-epoxyhexanoyl residue of CDAs. This was verified by detailed analysis of the MS/MS spectra of the daCDAs in comparison to the CDAs. The major CDA compounds present in calcium ion-supplemented agar medium of co-cultures were daCDAs, thus suggesting that Streptomyces sp. MG7-G1 expresses a deacylase that degrades CDAs.     

Identification of Fluorinases from Streptomyces sp MA37, Norcardia brasiliensis,and Actinoplanes sp N902‐109 by Genome Mining

The fluorinase is an enzyme that catalyses the combination of S‐adenosyl‐L ‐methionine (SAM) and a fluoride ion to generate 5′‐fluorodeoxy adenosine (FDA) and L ‐methionine through a nucleophilic substitution reaction with a fluoride ion as the nucleophile. It is the only native fluorination enzyme that has been characterised. The fluorinase was isolated in 2002 from Streptomyces cattleya, and, to date, this has been the only source of the fluorinase enzyme. Herein, we report three new fluorinase isolates that have been identified by genome mining. The novel fluorinases from Streptomyces sp. MA37, Nocardia brasiliensis, and an Actinoplanes sp. have high homology (80–87 % identity) to the original S. cattleya enzyme. They all possess a characteristic 21‐residue loop. The three newly identified genes were overexpressed in E. coli and shown to be fluorination enzymes. An X‐ray crystallographic study of the Streptomyces sp. MA37 enzyme demonstrated that it is almost identical in structure to the original fluorinase. Culturing of the Streptomyces sp. MA37 strain demonstrated that it not only also elaborates the fluorometabolites, fluoroacetate and 4‐fluorothreonine, similar to S. cattleya, but this strain also produces a range of unidentified fluorometabolites. These are the first new fluorinases to be reported since the first isolate, over a decade ago, and their identification extends the range of fluorination genes available for fluorination biotechnology.     

Multifactorial Approach to Biosurfactant Production by Adaptive Strain Candida tropicalis MTCC 230 in the Presence of Hydrocarbons

In this study, Candida tropicalis MTCC 230 was used to adapted in hydrocarbon along with glucose for biosurfactant production, showing diauxic growth during the production. Biosurfactant was characterized through TLC and FTIR analysis as surfactin, a lipopeptide. Process parameters were optimized one factor at a time, showing the highest emulsification index (%E₂₄) at 54 %. The production of biosurfactant was enhanced by using biostatistically based experimental design with the interactive effect of different parameters. On the basis of Placket–Burman design, four factors, hydrocarbon, ammonium chloride, microelements and temperature are found to be significant (P < 0.05) for the production of biosurfactant. A second order polynomial regression model in central composite design estimated the maximum biosurfactant production in terms of the emulsification index (%E₂₄). The optimum combination of different parameters for the biosurfactant production, obtained for hydrocarbon, ammonium chloride, microelements and temperature are 81.41 %, 1.63 (g/l), 1.69 (g/l) and 35.25 °C, respectively. The biosurfactant production was increased twofold after optimization and selection of interactive parameters by response surface methodology.     

Biosurfactant Production by Bacillus tequilensis ZSB10: Structural Characterization,Physicochemical, and Antifungal Properties

A new biosurfactant was obtained from a moderately halophilic bacterium identified as Bacillus tequilensis ZSB10 that was isolated from a saline water pond located in Tehuacan-Cuicatlan valley, Mexico. A kinetic analysis of the bacterial growth of the ZSB10 strain showed a maximum growth at 24 h regardless of the initial pH (5, 7.4, and 9). The best results were found at pH = 7.4 in terms of bacterial growth, besides which the produced biosurfactant showed emulsifying and surfactant properties with an emulsification index (E₂₄) and surface tension change (ΔST) of 54 ± 0% and 26 mN m⁻¹, respectively. Extracted ZSB10 crude biosurfactant had a yield of 106 ± 6 mg L⁻¹, an E₂₄ = 58.4 ± 0.2%, and a ΔST = 26 mN m⁻¹ with a critical micelle concentration (CMC) of 44.82 mg L⁻¹. Also, its structure was characterized by MALDI-TOF mass spectrometry as a surfactin, iturin A, and fengycin mixture whose main isoform was leu/ile-7 C₁₅ surfactin [M + Na]⁺. Finally, the ZSB10 crude biosurfactant showed antifungal activity against Helminthosporium sp., with a 79.3% growth inhibition and an IC₅₀ of 1.37 mg per disc. Therefore, this biosurfactant could be used as biopesticide.     

Screening and identification of Pseudomonas aeruginosa AB4 for improved production,characterization and application of a glycolipid biosurfactant using low‐cost agro‐based raw materials

BACKGROUND: The study is focused on (i) screening and taxonomic identity of a bacterial strain for biosurfactant production, and (ii) evaluation of its potential for production of a biosurfactant using agro‐based feedstock(s) and characterization of it for application in the removal of heavy metals. RESULTS: The production of biosurfactant by an isolate Pseudomonas aeruginosa AB4 (identified on the basis of 16S rRNA analysis) using various cost‐effective substrates were examined at conditions 40 °C, 120 rpm for 7 days. It revealed maximum (40 gL^?1) rhamnolipids production and 46% reduction of initial surface tension. Its optimum production was achieved at (i) C:N ratio 10:0.6, (ii) pH 8.5 and (iii) 40 °C. The cell–free supernatant examined for biosurfactant activity by (i) haemolytic assay, (ii) CTAB‐ methylene blue assay, (iii) drop collapse test, (iv) oil spreading technique and (v) EI 24 assay showed its glycolipid nature and stable emulsification. Analysis of partially purified rhamnolipids by (i) thin layer chromatography (TLC), (ii) high performance thin layer chromatography (HPTLC), (iii) high performance liquid chromatography (HPLC), (iv) Fourier transform infrared (FT‐IR) and (v) gas chromatography–mass spectrometry (GC‐MS) confirmed its structure as methyl ester of 3‐hydroxy decanoic acid (a glycolipid) with two major structural congeners (Rha‐C₁₀‐C₁₀ and Rha‐C₁₀‐C₈) of mono‐rhamnolipids. Finally, it showed sequestration of Cd and Pb, suggesting its application in biosurfactant‐assisted heavy metal bioremediation. CONCLUSION: This work has screened and identified a bacterium with superior biosurfactant production capabilities, characterized the glycolipidic biosurfactants as rhamnolipid and indicated the feasibility of biosurfactant production using novel renewable, relatively inexpensive and easily available resources such as non‐edible vegetable de‐oiled seed cakes and showed its utility in remediation of heavy metals. Copyright © 2010 Society of Chemical Industry     

Structural characterization of a biosurfactant produced by Bacillus subtilis at 45°C

Structural and biochemical characterization of a biosurfactant produced by Bacillus subtilis under thermophilic conditions was performed. Preliminary structural determination of CHCl₃/CH₃OH (65∶15) extracts by thin-layer chromatographic reagents showed it to be identical to surfactin. Also, the infrared, ¹H nuclear magnetic resonance, and mass spectroscopy analysis confirmed it to be identical to surfactin. Biochemically, the surfactant was a lipopeptide-containing lipid (17.05%) and protein (13.2%). The surfactant yielded a minimal aqueous surface-tension value of 28 dyne/cm and an interfacial tension value at 0.1% concentration of 0.2 dyne/cm against diesel oil. The critical micelle concentration of the surfactant was 35 mg/L. The biosurfactant exhibited an emulsification value (E ₂₄) of 90 against diesel oil and a sand-pack oil recovery of 62%. It has potential application in microbial-enhanced oil recovery in thermophilic, alkaline, acidic, and halophilic environments.     

Conversion of Phosphatidylcholine to Phosphatidylglycerol with Phospholipase D and Glycerol

When phosphatidylcholine (PtdCho) is acted upon by the enzyme phospholipase D (PLD) in the presence of glycerol and water, at least two products can arise: phosphatidic acid (PtdOH) from hydrolysis and PtdGly from transphosphatidylation. Commercial PLD preparations from Streptomyces chromofuscus, Streptomyces sp., and cabbage were examined for their ability to selectively promote PtdGly formation in a two phase aqueous-organic solvent system. Factors examined were enzyme amount, pH, glycerol concentration, and the type of organic solvent. The reaction of PtdCho to give products such as PtdGly was followed by HPLC using a stationary phase consisting of a polymerized poly (vinyl alcohol) on silica gel with ELSD. The identities of all products were confirmed by retention times and HPLC-MS analyses. Under all tested conditions PLD from S. chromofuscus gave at most a 15% yield of PtdGly. Higher amounts of added glycerol inhibited this PLD. Nearly quantitative conversion to PtdGly was obtained with cabbage PLD when the mol ratio of glycerol to PtdCho was at least 64 (mol water/glycerol = 105). With PLD from Streptomyces sp. a nearly quantitative yield of PtdGly was obtained when the mol ratio of glycerol to PtdCho was at least 5.3 (mol water/glycerol = 1,266), demonstrating that this PLD had a higher selectivity for glycerol than cabbage PLD. When the glycerol concentration was very low, the level of PtdOH increased, and cardiolipin (diphosphatidylglycerol) was generated. The highest mol ratio PtdGly to PtdOH was observed when the solvents isopropyl ether or dichloromethane were used. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.     

Application of Imine Reductases (IREDs) in Micro‐Aqueous Reaction Systems

Here we present the applicability of different imine reductases (IREDs) in micro‐aqueous reaction systems. Subjects of the study were the IREDs from Streptomyces aurantiacus (SaIR), Streptomyces sp. GF3587 (RGF3587IR), Streptomyces kanamyceticus (SkIR), Streptomyces ipomoeae 91‐03 (SiIR), Streptomyces sp. GF3546 (SGF3546IR), and Paenibacillus elgii B69 (PeIR). The IREDs were overexpressed in Escherichia coli (E. coli) cells and used directly after lyophilization. Several organic solvents and buffer amounts were screened for the reduction of the two substrates β‐carboline harmane and 1‐methyl‐3,4‐dihydroisoquinoline to the corresponding amines. Cyclopentyl methyl ether (CPME) proved to be the best solvent choice for the envisaged reduction. In addition, CPME is currently referred to as an environmentally benign solvent. Optimized reaction conditions were applied to 20 mM of the hardly water soluble substrates, leading to good conversions (up to 96%) and excellent enantiomeric excesses (>99%) in the best cases. The use of micro‐aqueous reaction systems opens the way to further applications of IREDs with hardly water soluble substrates.

     

Performance evaluation of batch and unsteady state fed‐batch reactor operations for the production of a marine microbial surfactant

BACKGROUND: Biosurfactants are microbially derived surface‐active and amphipathic molecules produced by various microorganisms. These versatile biomolecules can find potential applications in food, cosmetics, petroleum recovery and biopharmaceutical industries. However, their commercial use is impeded by low yields and productivities in fermentation processes. Thus, an attempt was made to enhance product yield and process productivity by designing a fed‐batch mode reactor strategy. RESULTS: Biosurfactant (BS) production by a marine bacterium was performed in batch and fed‐batch modes of reactor operation in a 3.7 L fermenter. BS concentration of 4.61 ± 0.07 g L^?1 was achieved in batch mode after 22 h with minimum power input of 33.87 × 10³ W, resulting in maximum mixing efficiency. The volumetric oxygen flow rate (K_La) of the marine culture was about 0.08 s^?1. BS production was growth‐associated, as evident from fitting growth kinetics data into the Luedeking‐Piret model. An unsteady state fed batch (USFB) strategy was employed to enhance BS production. Glucose feeding was done at different flow rates ranging from 3.7 mL min^?1 (USFB‐I) to 10 mL min^?1 (USFB‐II). USFB‐I strategy resulted in a maximum biosurfactant yield of 6.2 g l^?1 with an increment of 35% of batch data. The kinetic parameters of USFB‐I were better than those from batch and USFB‐II. CONCLUSION: Comparative performance evaluation of batch and semi‐continuous reactor operations was accomplished. USFB‐I operation improved biosurfactant production by about 35% over batch mode. USFB‐I strategy was more kinetically favorable than batch and USFB‐II. © 2012 Society of Chemical Industry     

Detergent Compatible Extracellular Lipase from Streptomyces cellulosae AU‐10: A Green Alternative for the Detergent Industry

Enzymes can decrease the environmental and economic load of detergent products by reducing the amount of chemicals used in detergents and by allowing washing at ambient temperatures. In this study, Streptomyces cellulosae AU‐10 (GenBank accession number: MG780240) lipase was purified 7.08‐fold with 68% yield using an aqueous 2‐phase system. The Streptomyces sp. AU‐10 lipase showed maximal activity at pH 9.0 and 40 °C. Hundred percent activities were measured in the pH range from 9.0 to 11.0 for 1 h. The enzyme was also highly stable at 30–50 °C. The values of K_m and V_max were calculated as 0.34 mM and 0.83 mM min^?1, respectively. The lipase has high hydrolytic activity for olive oil and sunflower oil. The effect of ethylenediamine tetraacetic acid on the enzyme has shown that the lipase is a metalloenzyme. The activity increased in the presence of Fe²⁺, Cu²⁺, and various boron compounds. The enzyme has shown a good stability not only with surfactants but also with oxidizing agents. In addition, activities in the presence of Omo, Ariel, Tursil, Pril, and Fairy were measured as 108.8%, 115.6%, 98.35%, 140.4%, and 107.6%, respectively. Considering its remarkable ability, the S. cellulosae AU‐10 lipase can be considered as a potential additive in the detergent industry.     

Alanine Scan of the Peptide Antibiotic Feglymycin: Assessment of Amino Acid Side Chains Contributing to Antimicrobial Activity

The antibiotic feglymycin is a linear 13‐mer peptide synthesized by the bacterium Streptomyces sp. DSM 11171. It mainly consists of the nonproteinogenic amino acids 4‐hydroxyphenylglycine and 3,5‐dihydroxyphenylglycine. An alanine scan of feglymycin was performed by solution‐phase peptide synthesis in order to assess the significance of individual amino acid side chains for biological activity. Hence, 13 peptides were synthesized from di‐ and tripeptide building blocks, and subsequently tested for antibacterial activity against Staphylococcus aureus strains. Furthermore we tested the inhibition of peptidoglycan biosynthesis enzymes MurA and MurC, which are inhibited by feglymycin. Whereas the antibacterial activity is significantly based on the three amino acids D ‐Hpg1, L ‐Hpg5, and L ‐Phe12, the inhibitory activity against MurA and MurC depends mainly on L ‐Asp13. The difference in the position dependence for antibacterial activity and enzyme inhibition suggests multiple molecular targets in the modes of action of feglymycin.     

Chicken Tallow,a Renewable Source for the Production of Biosurfactant by Yarrowia lipolytica MTCC9520, and its Application in Silver Nanoparticle Synthesis

The present study is focused on the production of a biosurfactant using Yarrowia lipolytica MTCC 9520 by employing inexpensive lipid waste, chicken tallow from slaughterhouses. Plackett–Burman and Box–Behnken Design analyses were adopted for preliminary screening of medium variables and further optimization. The maximal yield of 4.4 g L⁻¹ of the biosurfactant was obtained from the optimized medium. The highest emulsification activity was found to be 55%, and the surface tension decreased to 37 mN m⁻¹ at the end of 96 h. The critical micelle concentration of the biosurfactant was calculated as 1.2%. The produced biosurfactant was characterized as cationic lipoprotein in type, and the proteins present in the biosurfactant were observed to have molecular weights between 75 and 100 kDa. The fatty acids composition of the biosurfactant was detected by gas chromatography–mass spectrometry (GC–MS) analysis. Fourier transform infra red (FTIR) and nuclear magnetic resonance (NMR) analysis confirmed the lipoprotein nature of the extracted biosurfactant. Thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis revealed the thermostable nature of the extracted biosurfactant. Surface plasmon resonance vibration peak at 421 nm was observed for the surfactant-stabilized silver nanoparticles (AgNP) through UV–Vis spectrophotometry. The average particle size of the synthesized AgNP was calculated as 7.2 ± 0.4 nm from transmission electron microscopy (TEM) analysis. Energy dispersive x-ray (EDX) spectroscopy exhibited the presence of silver in the synthesized nanoparticles. The zeta potential value of the synthesized AgNP was measured as −22.2 mV, and the polydispersity index was found as 2.3 through dynamic light scattering (DLS) analysis.     

Antifungal Activity and Biosynthetic Potential of New Streptomyces sp. MW-W600-10 Strain Isolated from Coal Mine Water

Crop infections by fungi lead to severe losses in food production and pose risks for human health. The increasing resistance of pathogens to fungicides has led to the higher usage of these chemicals, which burdens the environment and highlights the need to find novel natural biocontrol agents. Members of the genus Streptomyces are known to produce a plethora of bioactive compounds. Recently, researchers have turned to extreme and previously unexplored niches in the search for new strains with antimicrobial activities. One such niche are underground coal mine environments. We isolated the new Streptomyces sp. MW-W600-10 strain from coal mine water samples collected at 665 m below ground level. We examined the antifungal activity of the strain against plant pathogens Fusarium culmorum DSM62188 and Nigrospora oryzae roseF7. Furthermore, we analyzed the strain’s biosynthetic potential with the antiSMASH tool. The strain showed inhibitory activity against both fungi strains. Genome mining revealed that it has 39 BGCs, among which 13 did not show similarity to those in databases. Additionally, we examined the activity of the Streptomyces sp. S-2 strain isolated from black soot against F. culmorum DSM62188. These results show that coal-related strains could be a source of novel bioactive compounds. Future studies will elucidate their full biotechnological potential.     

Biomonitoring of biosurfactant production by green fluorescent protein‐marked Bacillus subtilis W1012

BACKGROUND: Biosurfactant production was investigated using two strains of Bacillus subtilis, one being a reference strain (B. subtilis 1012) and the other a recombinant of this (B. subtilis W1012) made able to produce the green fluorescent protein (GFP). RESULTS: Batch cultivations carried out at different initial levels of glucose (G₀) in the presence of 10 g L^?1 casein demonstrated that the reference strain was able to release higher levels of biosurfactants in the medium at 5.0≤G₀≤10 g L^?1 (B_max = 104–110 mg L^?1). The recombinant strain exhibited slightly lower levels of biosurfactants (B_max = 90–104 mg L^?1) but only at higher glucose concentrations (G₀ ≥ 20 g L^?1). Under these nutritional conditions, the fluorescence intensity linked to the production of GFP was shown to be associated with the cell concentration even after achievement of the stationary phase. CONCLUSION: The ability of the genetically‐modified strain to simultaneously overproduce biosurfactant and GFP even at low biomass concentration makes it an interesting candidate for use as a biological indicator to monitor indirectly the biosurfactant production in bioremediation treatments. Copyright © 2008 Society of Chemical Industry     

Preparation of Phosphatidylated Terpenes via Phospholipase D-Mediated Transphosphatidylation

Terpenes such as geraniol, geranylgeraniol, farnesol, and phytol are known as functional compounds which exhibit anticancer effects and activate nuclear receptors. For the application of functional terpenes in various fields, including the cosmetic and food industries, we attempted to synthesize phosphatidylated terpenes (terpene-PLs) by using phospholipase D (PLD). Transphosphatidylation of phosphatidylcholine with terpenes was carried out using PLD in a biphasic system containing ethyl acetate/water or in an aqueous system without organic solvent. The yield of terpene-PL increased with the reaction time and the amount of PLD in both the biphasic and aqueous systems. Further, the yield of terpene-PL in the aqueous system was higher than that in the biphasic system. In addition, among four PLDs from Streptomyces sp., Streptomyces chromofuscus, cabbage, and peanut, only the PLD from Streptomyces sp. could synthesize terpene-PL. The reaction yield, based on substrate phospholipid, of phosphatidylgeraniol reached 90 mol% under the following optimal reaction conditions: 50 μmol soyPC; 2,000 μmol geraniol; 1.6 U PLD; 0.8 ml of 0.2 M sodium acetate buffer (pH 5.6); temperature, 37 °C ; and reaction time, 24 h. The reaction yields of phosphatidylfarnesol, phosphatidylgeranylgeraniol, and phosphatidylphytol were 73, 54, and 17 mol%, respectively.     

Effect of temperature on the stereoselectivity of phospholipase D toward glycerol in the transphosphatidylation of phosphatidylcholine to phosphatidylglycerol

In this study, the effect of temperature on the stereoselectivity of phospholipase D (PLD) toward the two primary hydroxyl groups of glycerol in the transphosphatidylation reaction of phosphatidylcholine to phosphatidylglycerol (PtdGro) was investigated. For this purpose, PLD from bacteria (Streptomyces septatus TH-2, S. halstedii subsp. scabies K6, and Actinomadura sp.) and cabbage were tested. At the reaction temperatures employed (0–60°C), the proportions of the two PtdGro diastereomers, namely, 1,2-dioleoyl-sn-glycero-3-phospho-3′-sn-glycerol (R,R configuration) and 1,2-dioleoyl-sn-glycero-3-phosphol-1′-sn-glycerol (R,S configuration), which were produced with PLD from Streptomyces TH-2 and Actinomadura sp., changed gradually from 50% R,R and 50% R,S at 50–60°C to 70% R,R and 30% R,S at O°C. These alterations suggested that the stereoselectivity of the bacterial PLD toward the two primary hydroxyl groups of prochiral glycerol was significantly influenced by reaction temperature. PLD from Streptomyces K6 showed relatively little effect of temperature on stereoselectivity, giving 65–69% R,R in the temperature range of 60–10°C examined. The plots of In ([R,R]/[R,S]) vs. 1/T gave good linear fits for these three bacterial PLD. No temperature effect was observed for cabbage PLD, which gave an almost equimolar mixture of the R,R and R,S diastereomers in the range from 0 to 40°C. The temperature-dependent change in enantiomeric selectivity of the bacterial PLD promises potentially profitable commercial exploitation.     

Aromatic Polyketide GTRI‐02 is a Previously Unidentified Product of the act Gene Cluster in Streptomyces coelicolor A3(2)

The biosynthesis of aromatic polyketides derived from type II polyketide synthases (PKSs) is complex, and it is not uncommon that highly similar gene clusters give rise to diverse structural architectures. The act biosynthetic gene cluster (BGC) of the model actinomycete Streptomyces coelicolor A3(2) is an archetypal type II PKS. Here we show that the act BGC also specifies the aromatic polyketide GTRI‐02 ( 1 ) and propose a mechanism for the biogenesis of its 3,4‐dihydronaphthalen‐1(2H)‐one backbone. Polyketide 1 was also produced by Streptomyces sp. MBT76 after activation of the act‐like qin gene cluster by overexpression of the pathway‐specific activator. Mining of this strain also identified dehydroxy‐GTRI‐02 ( 2 ), which most likely originated from dehydration of 1 during the isolation process. This work shows that even extensively studied model gene clusters such as act of S. coelicolor can still produce new chemistry, offering new perspectives for drug discovery.     

Culture Medium Evaluation Using Low-Cost Substrate for Biosurfactants Lipopeptides Production by Bacillus amyloliquefaciens in Pilot Bioreactor

Total biosurfactant production by Bacillus amyloliquefaciens IT45 was evaluated with different substrates concentrations in a culture medium. A central composite design (CCD) was developed to evaluate the influence of variables, including glucose syrup, yeast extract, and calcium chloride, on surface tension (ST), total biosurfactant production, and residual sugar (RS). As a result, the best observed results for ST, RS, and total biosurfactant production were 30 mN m⁻¹, 31%, and 5.5 g L⁻¹, respectively, after 48 h of fermentations carried out in batch operation process. Characterization of the biosurfactant identified the presence of surfactin. To validate the CCD experiments, fermentations were conducted in a 40 L pilot bioreactor. For this fermentation, the cellular growth was 3.0 × 10⁹ CFU mL⁻¹, surfactin production was 0.55 g L⁻¹, and RS was 28%. The results demonstrate that B. amyloliquefaciens IT45 has the potential to produce biosurfactants and does not require high concentrations of carbon and nitrogen sources for its development.