High mono-rhamnolipids production by a novel isolate Pseudomonas aeruginosa LP20 from oily sludge: characterization, optimization, and potential application.

This study aims to isolate microbial strains for producing mono-rhamnolipids with high proportion. Oily sludge is rich in petroleum and contains diverse biosurfactant-producing strains. A biosurfactant-producing strain LP20 was isolated from oily sludge, identified as Pseudomonas aeruginosa based on phylogenetic analysis of 16S rRNA. High-performance liquid chromatography-mass spectrometry results indicated that biosurfactants produced from LP20 were rhamnolipids, mainly containing Rha-C8-C10, Rha-C10-C10, Rha-Rha-C8-C10, Rha-Rha-C10-C10, Rha-C10-C12:1, and Rha-C10-C12. Interestingly, more mono-rhamnolipids were produced by strain LP20 with a relative abundance of 64.5%. Pseudomonas aeruginosa LP20 optimally produced rhamnolipids at a pH of 7.0 and a salinity of 0.1% using glycerol and nitrate. The culture medium for rhamnolipids by strain LP20 was optimized by response surface methodology. LP20 produced rhamnolipids up to 6.9 g L-1, increased by 116%. Rhamnolipids produced from LP20 decreased the water surface tension to 28.1 mN m-1 with a critical micelle concentration of 60 mg L-1. The produced rhamnolipids emulsified many hydrocarbons with EI24 values higher than 56% and showed antimicrobial activity against Staphylococcus aureus and Cladosporium sp. with inhibition rates 48.5% and 17.9%, respectively. Pseudomonas aeruginosa LP20 produced more proportion of mono-rhamnolipids, and the LP20 rhamnolipids exhibited favorable activities and promising potential in microbial-enhanced oil recovery, bioremediation, and agricultural biocontrol.

Improving Rhamnolipids Biosynthesis in Pseudomonas sp. L01 through Atmospheric and Room-Temperature Plasma (ARTP) Mutagenesis.

Biosurfactants have significant applications in various industries, including microbial-enhanced oil recovery (MEOR). While the state-of-the-art genetic approaches can generate high-yield strains for biosurfactant production in fermenters, there remains a critical challenge in enhancing biosurfactant-producing strains for use in natural environments with minimal ecological risks. The objectives of this work are enhancing the strain's capacity for rhamnolipids production and exploring the genetic mechanisms for its improvement. In this study, we employed atmospheric and room-temperature plasma (ARTP) mutagenesis to enhance the biosynthesis of rhamnolipids in Pseudomonas sp. L01, a biosurfactant-producing strain isolated from petroleum-contaminated soil. Following ARTP treatment, we identified 13 high-yield mutants, with the highest yield of 3.45 ± 0.09 g/L, representing a 2.7-fold increase compared to the parent strain. To determine the genetic mechanisms behind the enhanced rhamnolipids biosynthesis, we sequenced the genomes of the strain L01 and five high-yield mutants. A comparative genomic analysis suggested that mutations in genes related to the synthesis of lipopolysaccharides (LPS) and the transport of rhamnolipids may contribute to the improved biosynthesis. To the best of our knowledge, this is the first instance of utilizing the ARTP approach to improve rhamnolipid production in Pseudomonas strains. Our study provides valuable insights into the enhancement of biosurfactant-producing strains and the regulatory mechanisms of rhamnolipids biosynthesis.

Glycerol or crude glycerol as substrates make Pseudomonas aeruginosa achieve anaerobic production of rhamnolipids.

BACKGROUND: The anaerobic production of rhamnolipids is significant in research and application, such as foamless fermentation and in situ production of rhamnolipids in the anoxic environments. Although a few studies reported that some rare Pseudomonas aeruginosa strains can produce rhamnolipids anaerobically, the decisive factors for anaerobic production of rhamnolipids were unknown. RESULTS: Two possible hypotheses on the decisive factors for anaerobic production of rhamnolipids by P. aeruginosa were proposed, the strains specificity of rare P. aeruginosa (hypothesis 1) and the effect of specific substrates (hypothesis 2). This study assessed the anaerobic growth and rhamnolipids synthesis of three P. aeruginosa strains using different substrates. P. aeruginosa strains anaerobically grew well using all the tested substrates, but glycerol was the only carbon source that supported anaerobic production of rhamnolipids. Other carbon sources with different concentrations still failed for anaerobic production of rhamnolipids by P. aeruginosa. Nitrate was the excellent nitrogen source for anaerobic production of rhamnolipids. FTIR spectra analysis confirmed the anaerobically produced rhamnolipids by P. aeruginosa using glycerol. The anaerobically produced rhamnolipids decreased air-water surface tension to below 29.0 mN/m and emulsified crude oil with EI24 above 65%. Crude glycerol and 1, 2-propylene glycol also supported the anaerobic production of rhamnolipids by all P. aeruginosa strains. Prospects and bottlenecks to anaerobic production of rhamnolipids were also discussed. CONCLUSIONS: Glycerol substrate was the decisive factor for anaerobic production of rhamnolipids by P. aeruginosa. Strain specificity resulted in the different anaerobic yield of rhamnolipids. Crude glycerol was one low cost substrate for anaerobic biosynthesis of rhamnolipids by P. aeruginosa. Results help advance the research on anaerobic production of rhamnolipids, deepen the biosynthesis theory of rhamnolipids and optimize the anaerobic production of rhamnolipids.

Intradural Extramedullary Nerve Sheath Myxoma of the Cervical Spine: A Case Report and Review of Literature.

Background: Nerve sheath myxoma is a rare benign soft tissue tumor. Intraspinal nerve sheath myxomas are rare. Only 8 cases of intraspinal nerve sheath myxoma have been reported to date, and no case of nerve sheath myxoma has been reported in the cervical spinal canal. Herein, we reported the first case of intradural extramedullary nerve sheath myxoma in the cervical spinal canal of a 57-year-old man, including its complete clinical course and radiological findings. Case Presentation: A 57-year-old male patient presented with numbness in his left finger without any obvious inducement for 3 years. CT and contrast-enhanced magnetic resonance imaging (MRI) of the spine were performed. Based on the radiological examinations, a diagnosis of schwannoma was initially made. However, nerve sheath myxoma was finally confirmed by histopathological and immunohistochemical examinations. Complete tumor excision at the C1-2 level was performed. Then, the patient recovered well, and the numbness of his left finger disappeared during the later follow-up after the surgery. Conclusion: Nerve sheath myxoma should receive diagnostic consideration for an extramedullary subdural lesion that is a clear boundary mass characterized by isointensity on T1-weighted images, heterogeneous intensity on T2-weighted images, obvious peripheral enhancement, and a growing tendency toward the intervertebral foramen.

Athermalization of dual-waveband infrared systems containing diffractive optical elements via optical-digital joint design.

Because of material limitations, achieving an athermal design for dual-waveband infrared systems is difficult. This study integrates single-layer diffractive elements to reduce the volume and weight of such a design and introduces optical-digital joint methods to eliminate the impact of low diffraction efficiency. To achieve athermalization, temperature polychromatic integral diffraction efficiency and temperature integral wavelength weight are incorporated in the point spread function (PSF) model. Influence of low diffraction efficiency is eliminated via subsequent algorithm processing. Accordingly, athermal design and processing of a cooled dual-waveband infrared system is achieved and verified via experimental results.

Human adipose-derived mesenchymal stem cells inhibit proliferation and induce apoptosis of human gastric cancer HGC-27 cells.

The aim of this study was to explore the effects of human adipose-derived mesenchymal stem cells (ASCs) on the growth of gastric cancer cells in vivo and vitro and its mechanism. ASCs were isolated from abandoned adipose tissues, and the surface markers were identified by flow cytometry. In vitro experiments, HGC-27 cells cultured in ASCs-conditioned medium (CM) were assigned as the experimental group, while HGC-27 cells cultured in normal medium were as the control group. MTT and colony formation assays were performed to detect cell viability and colony formatting ability, respectively. Annexin-V/PI assay, Western blot, and caspase-3 enzyme activity assay were performed to detect cells apoptosis. The isolated ASCs could be differentiated into adipocytes and osteoblasts in vitro. Flow cytometry showed that CD73 and CD105 were positively expressed in HGC-27 cells. Compared with the mice injected HGC-27 cells only, the tumor formation in mice injected both ASCs and HGC-27 cells was significantly smaller (P < 0.05). The colony formation ability in experimental group was 40.09% smaller than control group (P < 0.05) and the cell apoptosis rate in experimental group was higher than the control group (P < 0.05). Furthermore, the expressions of cleaved PARP, cleaved caspase-3 proteins, and caspase-3 enzyme viability in experimental group were significantly higher than those of control group (P < 0.05). In conclusion, ASCs can effectively inhibit the growth of HGC-27 cells by inducing apoptosis.

[Effect of N2O produced by indigenous denitrifiers in oil reservoir on the physical properties of crude oil]. / 油藏本源反硝化功能菌的产气作用(N2O)及对原油物性的影响.

The success of microbial enhanced oil recovery (MEOR) relies on complex microbial processes. Nevertheless, the contribution and mechanism of in-situ denitrification to microbial oil recovery remain unclear. In this study, eight denitrifying bacterial strains, designated T1, D1, D44, D46, D15, S1, S2 and S6, were isolated from the produced water of Xinjiang Oilfield, China, by a double layered plate method. The16S rDNA gene sequences of these denitrifying strains shared 100% similarity with Pseudomonas stutzeri (T1, D1, and D44), Pseudomonas putida (D46 and D15), and Pseudomonas aeruginosa (S1, S2, S6), respectively. The N2O production effects of these strains on the physical properties of crude oil were evaluated with batch experiment. Results showed that the highest total gas yield was observed with sucrose as carbon source, and the maximal concentration of N2O occurred with glycerol as carbon source. The denitrification process by these bacterial strains led to volume expansion and viscosity reduction of crude oil. Crude oil expansion rate was positively correlated with the concentration of N2O, with a correlation coefficient of 0.983, but not correlated with the volume of total gas production. Strain S1, S2, and S6 produced 530-730 mg·L-1 of surfactant using glycerol as ole carbon source, which could reduce surface tension and emulsify crude oil. However, these surfactant-producing strains produced less N2O, exhibited weaker effects on oil swelling and viscosity reduction, compared to the none-surfactant-producing denitrifying strains. Our results suggested that more attention should be paid to the ability of N2O production by denitrifying bacteria when exploiting microbial resources towards enhancing oil recovery.

Achromatic annular folded lens with reflective-diffractive optics.

This paper proposes an achromatic annular folded lens (AFL) with a reflective-diffractive optical element (RDOE). We derive novel mathematical models of the diffraction efficiency and polychromatic integral diffraction efficiency (PIDE) of the RDOE and an expression for its microstructure height. An AFL with an RDOE made of an optical plastic substrate material is designed in the visible waveband. To minimize the influence of incident angle on the diffraction efficiency and PIDE, the microstructure height is optimized. The design results indicate that the lateral color of the AFL is corrected, the modulation transfer function considering the diffraction efficiency is larger than 0.25 at 111 cycles/mm for all field of views. The hybrid AFL outperforms the conventional refractive imaging system in terms of the system size, volume, and image quality under the same specifications. It can be used in new-generation miniaturized imaging systems.

Design of dual-band infrared zoom lens with multilayer diffractive optical elements.

A mid-wave infrared (MWIR)/long-wave infrared (LWIR) dual-band zoom lens design with multilayer diffractive optical elements (MLDOEs) is presented. The mathematical relationship between the substrate material selection for dual-band MLDOE and polychromatic integral diffraction efficiency (PIDE) is deduced in the oblique incident situation, and further, a method for optimal selection of substrate material is proposed to obtain the high PIDE in an incident angle range. In the optimization process, the optimal substrate material combination is selected based on the proposed method, and the principle of lens material replacement is discussed. After optimization, the 5× hybrid dual-band infrared zoom system is obtained, which consists of seven lenses. The modulation transfer function values in all configurations are larger than 0.5 and 0.3 in MWIR and LWIR, respectively. The distortion values are less than 2% both in MWIR and LWIR for all configurations.

Optical athermalization in the visible waveband using the 1+∑ method.

In this paper, the 1+∑ method, which is based on the double-lens equivalent model, is proposed to achieve optical athermalization in the visible waveband. The glass in the system was replaced by calculating and analyzing the synthetic weights of the thermal power and chromatic power. A complex aerial camera with long focal length was designed over a temperature difference of 100°C. The results demonstrated that the designed system could maintain good image quality and stable optical performance under large temperature differences.

PSF model for diffractive optical elements with improved imaging performance in dual-waveband infrared systems.

Single-layer diffractive optical elements (SLDOEs) have advantages in terms of configuration, fabrication, range of angles and cost; however, the diffraction efficiency decreases sharply with wavelength deviating from the design wavelength, especially for dual-waveband imaging, causing apparent image blur. We propose a point spread function (PSF) model affected by the diffraction efficiency, which is called PSFDOE, and a method of restoring the blurred image to improve imaging performance in dual-waveband infrared systems with an SLDOE. Then, a design example of cooled MWIR and LWIR is presented. Furthermore, imaging simulations with different grades noises and restorations are conducted. Results reveal that the PSFDOE model can significantly improve the image blur caused by the decreased diffraction efficiency.

Optimization method of multilayer diffractive optical elements with consideration of ambient temperature.

A method for the optimal design of multilayer diffractive optical elements (MLDOEs) with consideration of ambient temperature is presented to improve the image quality over the entire temperature range. The relationship between diffraction efficiency and temperature is analyzed, and an optimization process of surface relief height for the MLDOEs is given. A practical 3-5 µm athermal hybrid optical system with a double-layer diffractive optical element is designed in the temperature range from -20°C to 60°C, and the image quality of two hybrid optical systems with optimized MLDOE and original MLDOE is compared. The result shows that the comprehensive modulation transfer function is obviously improved in the whole working temperature range. This method can be used during the passive athermalization hybrid optical system design with MLDOEs.

Exopolysaccharide production by an indigenous isolate Pseudomonas stutzeri XP1 and its application potential in enhanced oil recovery.

In this study, a rapid and efficient method for screening biopolymer producers was established using 96-well plates. An indigenous biopolymer producer Pseudomonas stutzeri XP1 was isolated from Xinjiang oil reservoirs, China. Strain XP1 can grow and produce 16 g/l biopolymer using corn starch and nitrate. Produced biopolymer increased culture viscosity up to 2384 mPa s. Biopolymer showed rheological properties and pseudo-plastic behavior. The viscosity of 8 g/l biopolymer solution kept higher than 25 mPa s at 20-50 °C and pH values (5-9) and increased to 7600 mPa s with NaCl concentrations increasing to 2%. Gel permeation chromatography data showed that the biopolymer average molecular mass was 1.65 × 106 Da. Gas chromatography revealed that the monosaccharide composition in biopolymer was glucose. Core flooding experiments revealed that extra 13.56% of oil was recovered by in situ biopolymer production of strain XP1. Properties of strain XP1 and the biopolymer produced make them promising for enhanced oil recovery.

Design of a built-in baffle for a Ritchey-Chretien optical system.

A baffle effectively prevents direct rays of stray light from entering an optical system. Existing design methods can result in very long outer baffle lengths, increasing the weight and volume of the optical system, or large secondary mirror baffle sizes, increasing the central obscuration and resulting in the reduction of the illumination beam on the image. To overcome these challenges, a design method for a built-in baffle is presented. The designed built-in baffle for a typical Ritchey-Chretien optical system is compared with a conventionally designed baffle. The results show that when the length of outer baffle is shortened from 3456 to 2349.9 mm, the modulation transfer function (MTF) increases from 0.361 to 0.421 in case 1, and when the length is shortened from 3456 to 1924.2 mm, the MTF increases from 0.361 to 0.408 in case 2. Meanwhile, the stray light suppression capability is close to that of the traditional method.

Effect of the surface roughness on the efficiency of diffractive optical elements.

The proposed study aims to investigate the effect of surface roughness on the efficiency of diffractive optical elements (DOEs) used in imaging optical systems. A mathematical model describing the influence of surface roughness on diffraction efficiency and polychromatic integral diffraction efficiency (PIDE) is presented, and its effects are analyzed and simulated. Examples of single-layer DOEs containing PMMA substrate and multi-layer DOEs composed of a combination of PMMA and polycarbonate substrates for each layer used in the visible region are analyzed. The results can be used to analyze the effects of surface roughness on the diffraction efficiency and PIDE of DOEs.

Optimal design method on diffractive optical elements with antireflection coatings.

The effect of antireflection coatings on diffraction efficiency of diffractive optical elements (DOEs) was studied and the mathematical model of diffraction efficiency affected by antireflection coatings for DOEs is presented. We found antireflection coatings can cause a significant reduction on diffraction efficiency at the designed, or the central wavelength. In order to solve this problem, we proposed a method to keep 100% diffraction efficiency at the designed wavelength by ensuring the 2π phase induced by DOEs and the antireflection coatings. Diffraction efficiency affected by antireflection coatings for DOEs with consideration of antireflection coatings are simulated. Analysis results can be utilized for refractive-diffractive hybrid imaging optical system optimal design and image quality evaluation.

Substrate material selection method for multilayer diffractive optics in a wide environmental temperature range.

We present a substrate material selection method for multilayer diffractive optical elements (MLDOEs) to obtain high polychromatic integral diffraction efficiency (PIDE) in a wide environmental temperature range. The extended expressions of the surface relief heights for the MLDOEs are deduced with consideration of the influence of the environmental temperature. The PIDE difference Δη¯(λ) and PIDE change factor F are introduced to select a reasonable substrate material combination. A smaller value of Δη¯(λ) or F indicates a smaller decrease of the PIDE in a wide temperature range, and the corresponding substrate material combination is better. According to the deduced relation, double-layer and three-layer DOEs with different combinations are discussed. The results show that IRG26 and zinc sulfide is the best substrate material combination in the infrared waveband for double-layer DOEs, and polycarbonate is more reasonable than polymethyl methacrylate as the middle filling optical material for three-layer DOEs when the two substrate materials are the same.

Aberration and boresight error correction for conformal aircraft windows using the inner window surface and tilted fixed correctors.

A static solution to aberrations and boresight error for tilted conformal aircraft windows at different look angles is reported. The solution uses the inner window surface to correct the window aberrations at a 0° look angle and uses fixed correctors behind the window to correct the residual window aberrations at other look angles. Then, the boresight error for the window at different look angles is corrected by tilting the fixed correctors. The principle of the solution is discussed, and a design example shows that the solution is effective in correcting the aberrations and boresight error for a tilted conformal aircraft window at different look angles.

High diffraction efficiency of three-layer diffractive optics designed for wide temperature range and large incident angle.

A mathematical model of diffraction efficiency and polychromatic integral diffraction efficiency affected by environment temperature change and incident angle for three-layer diffractive optics with different dispersion materials is put forward, and its effects are analyzed. Taking optical materials N-FK5 and N-SF1 as the substrates of multilayer diffractive optics, the effect on diffraction efficiency and polychromatic integral diffraction efficiency with intermediate materials POLYCARB is analyzed with environment temperature change as well as incident angle. Therefore, three-layer diffractive optics can be applied in more wide environmental temperature ranges and larger incident angles for refractive-diffractive hybrid optical systems, which can obtain better image quality. Analysis results can be used to guide the hybrid imaging optical system design for optical engineers.

Draft genome sequence of Paenibacillus sp. strain A2.

Paenibacillus sp. strain A2 is a Gram-negative rod-shaped bacterium isolated from a mixture of formation water and petroleum in Daqing oilfield, China. This facultative aerobic bacterium was found to have a broad capacity for metabolizing hydrocarbon and organosulfur compounds, which are the main reasons for the interest in sequencing its genome. Here we describe the features of Paenibacillus sp. strain A2, together with the genome sequence and its annotation. The 7,650,246 bp long genome (1 chromosome but no plasmid) exhibits a G+C content of 54.2 % and contains 7575 protein-coding and 49 RNA genes, including 3 rRNA genes. One putative alkane monooxygenase, one putative alkanesulfonate monooxygenase, one putative alkanesulfonate transporter and four putative sulfate transporters were found in the draft genome.