scholarly journals Enhancing rhamnolipids production and exploring the mechanism of low-foaming fermentation under weakly acidic conditions

2020 ◽  
Author(s):  
Zhijin Gong ◽  
Ge Yang ◽  
Chengchuan Che ◽  
Jinfeng Liu ◽  
Meiru Si ◽  
...  
Keyword(s):  
Large Scale ◽  
Control Strategies ◽  
Strain Improvement ◽  
Mechanism Study ◽  
Foaming Ability ◽  
Lamellar Structures ◽  
Foaming Behavior ◽  
Acidic Conditions ◽  
Commercial Applications ◽  
Charged Ions

Abstract The commercial applications of rhamnolipids have seriously been impeded by the high cost of production caused by severe foaming. Effective low-foaming fermentation and mechanism study have become the most urgent requirement for the larger-scale rhamnolipids production. In this study, the low-foaming fermentation of rhamnolipids is realized by controlling fermentation at pH 5.5. Further, the rhamnolipids production is enhanced 0.9-fold by ultraviolet and ethyl methanesulfonate composite mutagenesis. To the best of our knowledge, this is the first report to enhance production of rhamnolipids by strain improvement under weakly acidic conditions. The mechanism exploration tests indicated that increasing surface tension and decreasing viscosity are conducive to reducing foaming ability of rhamnolipids fermentation. The decrease of negatively charged ions may weaken the electrostatic repulsion between charged substances adsorbed on membranes of bubbles such as rhamnolipids and cells, making liquid membranes prone to rupture. In addition, the vesicle or lamellar structures of rhamnolipids are formed under pH 5.0-6.0, weakening the foaming ability of rhamnolipids. The work reveals promising potentiality by genetic modification to enhance rhamnolipids production and is conducive to understanding the pH-associated foaming behavior as well as developing the more effective pH-associated control strategies for large-scale rhamnolipids production under weakly acidic conditions.

scholarly journals Enhancing rhamnolipid production and exploring the mechanisms of low-foaming fermentation under weak-acid conditions

2020 ◽  
Author(s):  
Zhijin Gong ◽  
Ge Yang ◽  
Chengchuan Che ◽  
Jinfeng Liu ◽  
Meiru Si ◽  
...  
Keyword(s):  
Large Scale ◽  
Control Strategies ◽  
Strain Improvement ◽  
Weak Acid ◽  
Scale Production ◽  
Mechanism Study ◽  
Foaming Ability ◽  
Large Scale Production ◽  
Foaming Behavior ◽  
Charged Ions

Abstract The commercialized applications of rhamnolipid has seriously impeded by high cost of production caused by severe foaming. Effective low-foaming fermentation and mechanism study have become the most urgent requirement for larger-scale production of rhamnolipid. In this study, the low-foaming fermentation was realized by controlling fermentation at pH 5.5. Further, the production of rhamnolipid was enhanced 0.9-fold by the ultraviolet and ethyl methanesulfonate composite mutagenesis. To the best of our knowledge, this was the first report to enhance production of rhamnolipid by strain improvement at weak-acid conditions. The mechanisms exploration tests indicated that increasing surface tension and decreasing viscosity were conducive to reduce foaming ability of rhamnolipid fermentation. The decrease of negatively charged ions may weaken the electrostatic repulsion between charged substances adsorbed membranes of bubbles such as rhamnolipid and cells, leading to the liquid membranes to rupture easily. In addition, the structure of vesicle or lamellar of rhamnolipid formed at pH5.0-6.0 may also weaken the foaming ability of rhamnolipid fermentation. The work revealed the promising potentiality for genetic modification to enhance the production of rhamnolipid and facilitated the understanding of pH-associated foaming behavior, as well as were conducive to develop a more effective pH-associated control strategies for large-scale production of rhamnolipid.

scholarly journals Estimating asymptomatic, undetected and total cases for the COVID-19 outbreak in Wuhan: a mathematical modeling study

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Xi Huo ◽  
Jing Chen ◽  
Shigui Ruan
Keyword(s):  
Disease Transmission ◽  
Large Scale ◽  
Transmission Rate ◽  
Control Strategies ◽  
Herd Immunity ◽  
Antibody Prevalence ◽  
Screening Process ◽  
Vaccination Programs ◽  
Prevalence Level ◽  
The Impact

Abstract Background The COVID-19 outbreak in Wuhan started in December 2019 and was under control by the end of March 2020 with a total of 50,006 confirmed cases by the implementation of a series of nonpharmaceutical interventions (NPIs) including unprecedented lockdown of the city. This study analyzes the complete outbreak data from Wuhan, assesses the impact of these public health interventions, and estimates the asymptomatic, undetected and total cases for the COVID-19 outbreak in Wuhan. Methods By taking different stages of the outbreak into account, we developed a time-dependent compartmental model to describe the dynamics of disease transmission and case detection and reporting. Model coefficients were parameterized by using the reported cases and following key events and escalated control strategies. Then the model was used to calibrate the complete outbreak data by using the Monte Carlo Markov Chain (MCMC) method. Finally we used the model to estimate asymptomatic and undetected cases and approximate the overall antibody prevalence level. Results We found that the transmission rate between Jan 24 and Feb 1, 2020, was twice as large as that before the lockdown on Jan 23 and 67.6% (95% CI [0.584,0.759]) of detectable infections occurred during this period. Based on the reported estimates that around 20% of infections were asymptomatic and their transmission ability was about 70% of symptomatic ones, we estimated that there were about 14,448 asymptomatic and undetected cases (95% CI [12,364,23,254]), which yields an estimate of a total of 64,454 infected cases (95% CI [62,370,73,260]), and the overall antibody prevalence level in the population of Wuhan was 0.745% (95% CI [0.693%,0.814%]) by March 31, 2020. Conclusions We conclude that the control of the COVID-19 outbreak in Wuhan was achieved via the enforcement of a combination of multiple NPIs: the lockdown on Jan 23, the stay-at-home order on Feb 2, the massive isolation of all symptomatic individuals via newly constructed special shelter hospitals on Feb 6, and the large scale screening process on Feb 18. Our results indicate that the population in Wuhan is far away from establishing herd immunity and provide insights for other affected countries and regions in designing control strategies and planing vaccination programs.

scholarly journals A Full-Newton AC-DC Power Flow Methodology for HVDC Multi-Terminal Systems and Generic DC Network Representation

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1658
Author(s):  
Leandro Almeida Vasconcelos ◽  
João Alberto Passos Filho ◽  
André Luis Marques Marcato ◽  
Giovani Santiago Junqueira
Keyword(s):  
Power Systems ◽  
Direct Current ◽  
Power Flow ◽  
Large Scale ◽  
Flow Problem ◽  
Control Strategies ◽  
Problem Formulation ◽  
Expansion Planning ◽  
Dc Power ◽  
Power Flow Problem

The use of Direct Current (DC) transmission links in power systems is increasing continuously. Thus, it is important to develop new techniques to model the inclusion of these devices in network analysis, in order to allow studies of the operation and expansion planning of large-scale electric power systems. In this context, the main objective of this paper is to present a new methodology for a simultaneous AC-DC power flow for a multi-terminal High Voltage Direct Current (HVDC) system with a generic representation of the DC network. The proposed methodology is based on a full Newton formulation for solving the AC-DC power flow problem. Equations representing the converters and steady-state control strategies are included in a power flow problem formulation, resulting in an expanded Jacobian matrix of the Newton method. Some results are presented based on HVDC test systems to confirm the effectiveness of the proposed approach.

scholarly journals Reduced Dosage of Methyl Bromide for Controlling Verticillium Wilt of Potato in Experimental and Commercial Plots

Plant Disease ◽  
1997 ◽  
Vol 81 (5) ◽  
pp. 469-474 ◽  
Author(s):  
A. Gamliel ◽  
A. Grinstein ◽  
Y. Peretz ◽  
L. Klein ◽  
A. Nachmias ◽  
...  
Keyword(s):  
Verticillium Wilt ◽  
Methyl Bromide ◽  
Large Scale ◽  
Field Experiments ◽  
Tuber Yield ◽  
Total Yield ◽  
Effective Control ◽  
Large Scale Field ◽  
Commercial Applications

The use of gas-impermeable films to reduce the dosage of methyl bromide (MB) required to control Verticillium wilt in potatoes was examined in field experiments, conducted in soils naturally infested with Verticillium dahliae. The incidence and severity of Verticillium wilt were significantly reduced (by 74 to 94%) by fumigation with MB at 50 g/m2 under standard low density polyethylene (LDPE) or at 25 g/m2 under gas-impermeable films. Fumigation at 25 g/m2 under LDPE was less effective. Disease severity was inversely correlated (r2 = 0.89 to 0.91) with chlorophyll content in the leaves. Fumigation also reduced (by 89 to 100%) stem colonization by the pathogen. Potato yield in the fumigated plots was significantly higher (26 to 69%), than in their nonfumigated counterparts, and was inversely correlated with disease index (r2 = 0.69 to 0.9). The percentage of high-value tubers (above 45 g) was 52 to 56% of total yield in the fumigated plots as compared with 32 to 40% in the nonfumigated controls. Thus, fumigation also improved the commercial quality of tuber yield. Effective control of V. dahliae and yield increases following MB fumigation at the recommended dosage or at a reduced dosage with gas-impermeable films was also observed in a consecutive crop. These results were verified in a large-scale field experiment using commercial applications, further demonstrating the feasibility of reducing MB dosages under farm conditions, without reducing its effectiveness in terms of disease control and yield improvement.

The Control Strategy Study of Doubly-Fed Wind Turbine Participated in Frequency Regulation

2012 ◽  
Vol 512-515 ◽  
pp. 788-793
Author(s):  
Xiao Hua Zhou ◽  
Ming Qiang Wang ◽  
Wei Wei Zou
Keyword(s):  
Wind Turbine ◽  
Control Strategy ◽  
Large Scale ◽  
Control Strategies ◽  
Frequency Control ◽  
Frequency Regulation ◽  
Strategy Study ◽  
Fuzzy Control Strategy ◽  
Doubly Fed ◽  
System Frequency

Traditional decoupling control strategy of doubly-fed induction generator (DFIG) wind turbine makes little contribution to system inertia and do not participate in the system frequency control, the synchronization of large-scale wind power requires wind turbine have the ability to participate in the regulation of power system frequency. This paper adds a frequency control segment to traditional DFIG wind turbine and considers the doubly-fed wind turbine operating on the state of the super-synchronous speed, by analysis the effect of inertia and proportional control strategies, a fuzzy control strategy which combines the advantages of the former two control strategies is proposed, simulation results show that this control strategy can more effectively improve the system frequency response.

scholarly journals Foaming of rhamnolipids fermentation: impact factors and fermentation strategies

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Zhijin Gong ◽  
Ge Yang ◽  
Chengchuan Che ◽  
Jinfeng Liu ◽  
Meiru Si ◽  
...  
Keyword(s):  
Production Process ◽  
Large Scale ◽  
Commercial Production ◽  
Impact Factors ◽  
Scale Production ◽  
Large Scale Production ◽  
Foaming Behavior ◽  
Production Strategies ◽  
Potential Applications ◽  
And Control

AbstractRhamnolipids have recently attracted considerable attentions because of their excellent biosurfactant performance and potential applications in agriculture, environment, biomedicine, etc., but severe foaming causes the high cost of production, restraining their commercial production and applications. To reduce or eliminate the foaming, numerous explorations have been focused on foaming factors and fermentation strategies, but a systematic summary and discussion are still lacking. Additionally, although these studies have not broken through the bottleneck of foaming, they are conducive to understanding the foaming mechanism and developing more effective rhamnolipids production strategies. Therefore, this review focuses on the effects of fermentation components and control conditions on foaming behavior and fermentation strategies responded to the severe foaming in rhamnolipids fermentation and systematically summarizes 6 impact factors and 9 fermentation strategies. Furthermore, the potentialities of 9 fermentation strategies for large-scale production are discussed and some further strategies are suggested. We hope this review can further facilitate the understanding of foaming factors and fermentation strategies as well as conducive to developing the more effective large-scale production strategies to accelerate the commercial production process of rhamnolipids.

Abstract 262: Derivation of Duchenne Muscular Dystrophy Disease Specific Cardiomyocytes From Patient Urine

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
Xuan Guan ◽  
David L Mack ◽  
Claudia M Moreno ◽  
Fernando Santana ◽  
Charles E Murry ◽  
...  
Keyword(s):  
Stem Cells ◽  
Human Urine ◽  
Large Scale ◽  
Lentiviral Vector ◽  
Cellular Reprogramming ◽  
Urine Samples ◽  
Pcr Analysis ◽  
Scale Production ◽  
Mechanism Study

Introduction: Human somatic cells can be reprogrammed into primitive stem cells, termed induced pluripotent stem cells (iPSCs). These iPSCs can be extensively expanded in vitro and differentiated into multiple functional cell types, enabling faithful preservation of individual’s genotype and large scale production of disease targeted cellular components. These unique cellular reagents thus hold tremendous potential in disease mechanism study, drugs screening and cell replacement therapy. Due to the genetic mutation of the protein dystrophin, many DMD patients develop fatal cardiomyopathy with no effective treatment. The underlying pathogenesis has not been fully elucidated. Hypothesis: We tested the hypothesis that iPSCs could be generated from DMD patients’ urine samples and differentiated into cardiomyocytes, recapitulating the dystrophic phenotype. Methods: iPSCs generation was achieved by introducing a lentiviral vector expressing Oct4, Sox2, c-Myc and Klf4 into cells derived from patient’s (n=1) and healthy volunteers’ (n=3) urine. Cardiomyocytes were derived by sequentially treating iPSCs with GSK3 inhibitor CHIR99021 and Wnt inhibitor IWP4. Differentiated cardiomyocytes were subjected to calcium imaging, electrophysiology recording, Polymerase Chain Reaction (PCR) analysis, and immunostaining. Results: iPSCs were efficiently generated from human urine samples and further forced to differentiate into contracting cardiomyocytes. PCR analysis and immunostaining confirmed the expression of a panel of cardiac markers. Both normal and patient iPSC derived cardiomyocytes exhibited spontaneous and field stimulated calcium transients (up to 2Hz), as well as action potentials with ventricular-like and nodal-like characteristics. Anti-dystrophin antibodies stained normal iPSC-derived cardiomyocyte membranes but did not react against DMD iPSC-derived cardiomyocytes. Conclusions: Cardiomyocytes can be efficiently generated from human urine, through the cellular reprogramming technology. DMD cardiomyocytes retained the patient’s genetic information and manifested a dystrophin-null phenotype. Functional assessments are underway to determine differences that may exist between genotypes.

scholarly journals Oral Tobaccco and Mortality in India

2016 ◽  
Vol 7 ◽  
pp. IJCM.S25889 ◽  
Author(s):  
Priya Mohan ◽  
Harry A. Lando
Keyword(s):  
Tobacco Control ◽  
Health Care Professionals ◽  
Large Scale ◽  
Control Strategies ◽  
Control Policy ◽  
Control Measures ◽  
Educational Institutions ◽  
Regional Studies ◽  
Gender And Education ◽  
Indian Context

This comprehensive review includes large-scale pan-India surveys and regional studies. Every aspect of smokeless tobacco, including variations in social, economic, demographic, gender, and education stratifiers, is presented. This evidence-based presentation thereby provides insight not only to assess the burden but can serve as a base, leading to the development and encouragement of research in closing the existing gaps in knowledge. It can also provide a track to formulate tobacco control strategies as well as to reinforce and potentially guide tobacco control policy aimed at addressing the tailored needs in the Indian context. The recommendations expand the tobacco control spectrum and are the first of their kind in the literature to focus on cessation programs as a paramedical subject to draw the attention of not only policymakers but also to integrate medical and dental educational institutions, health care professionals, and tobacco users to synergistically develop successful tobacco control measures.

scholarly journals Protection of Aluminum Foils against Environmental Corrosion with Graphene-Based Coatings

2021 ◽  
Vol 8 ◽  
pp. 18-28
Author(s):  
George Paterakis ◽  
George Anagnostopoulos ◽  
Labrini Sygellou ◽  
Costas Galiotis ◽  
◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Sulfuric Acid ◽  
Inhibition Efficiency ◽  
Lithium Perchlorate ◽  
Aluminum Foil ◽  
Corrosion Performance ◽  
Acidic Conditions ◽  
Corrosion Inhibition Efficiency ◽  
Commercial Applications ◽  
Lower Corrosion Rate

Commercial aluminum foils were coated by graphene oxide, and its functionalized derivatives and the corrosion performance of the coated specimens were examined in acidic conditions (lithium perchlorate and sulfuric acid). Electrochemical experiments have shown that all graphene oxide-coated specimens provided up to 96% corrosion inhibition efficiency with a corresponding lower corrosion rate compared to the bare aluminum foil. Our results clearly show that graphene-related materials offer viable alternatives for the protection of aluminum, and this opens up a number of possibilities for its use in a number of commercial applications.

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