Impact of oxygen supply on production of terpenoids by microorganisms: State of the art

Terpenoids are a class of high value-added natural products with a variety of biological functions.Genetically engineered microorganisms,such as those of Escherichia coli and Saccharomyces cerevisiae,have merits in producing plant or fungus-derived terpenoids,due to their mature genetic manipulation,simple nutrient demand and fast growth.Oxygen,as a key environmental factor,is particularly important to microbial metabolism and growth,and suitable oxygen supply is viewed as a prerequisite for realizing highly efficient production of terpenoids by engineered microorganisms.In this article,the role of oxygen in regulating terpenoid bioproduction is overviewed from the viewpoints of cellular carbon metabolism,energy metabolism and terpenoid anabolism.Strategies on adjusting oxygen availability to microorganisms,including genetic modification of cellular metabolism related with oxygen utilization,are summarized and discussed,to provide helpful information for further improvement of terpenoid biosynthesis by microbes.

An aviation oxygen supply system based on a mechanical ventilation model

At high altitudes, an Aviation Oxygen Supply System （AOSS） protects pilots from low pressure and hypoxia by continuously providing oxygen corresponding to the pilots＇ dynamic respiratory properties. An AOSS mainly consists of oxygen supercharging machines which are used in a high-altitude flight cabin to supply pressurized oxygen to pilots. Therefore, it is of great significance to study the airflow dynamic characteristics of an AOSS for safe, continuous, and efficient oxygen supply. In this paper, an AOSS is firstly simplified and considered as a mechanical ventilation system. Then, its corresponding mathematical model is constructed. Next, to verify the mathematical model, a prototype AOSS with a lung simulator is proposed for an experimental study. Afterwards, to build a foundation for the optimization of the AOSS, the airflow dynamic characteristics of an aircraft are analyzed, and the effects of key parameters on the respiration system are researched. Through experimental and simulation studies, it can be concluded that the mathematical model is effective. Subsequently, for stability during the respiration process, we consider setting the equivalent throttling areas of the inspiration and expiration pipelines smaller within certain limits; additionally, an excessively high oxygen supply pressure will disturb smooth airflow, and in a low-pressure environment, the pressure can be 84 cmH20 lower than the standard atmospheric pressure. This research can be referred to in the design of an oxygen supply system and the study on optimization of airflow dynamic characteristics.

A novel point source oxygen supply method for sleeping environment improvement at high altitudes

The hypoxic environment at high altitudes causes various sleep disorders.Diffuse oxygen enrichment is an effective way to alleviate sleep disorders and improve the built environment in high altitude areas.In this study,a novel point source local diffuse oxygen supply method was proposed to improve the sleeping oxygen environment.The oxygen supply performance was investigated by the computational fluid dynamics(CFD)method including the oxygen concentration and air velocity distributions.A sleeping experiment was conducted on the plateau to validate the CFD model.The occupied zone including the inhalation zone and the active zone was defined.The results showed that the oxygen concentration showed a rapid rise,then decreased slowly,and finally tended to be stable.The oxygen concentration after stabilization was remarkably influenced by indoor ventilation rate.The sleeping environment’s improvement was examined considering the oxygen enrichment efficiency,uniformity,stability and human comfort demand.The optimal strategies were recommended with a ventilation rate of 1 air change per hour,supplied oxygen concentration of 90%;and jet distance of 0.50 m.The study contributes to improving the oxygen environment and human sleep quality in an effective and energy-saving approach to the sustainable development of buildings in high altitude areas.

Effects of H_2O_2 on Oxygen Supply in the Process of DCA Fermentation

Long chain dicarboxylic acid (DCA) produced by Candida tropicalis is produced in an aerobic viscous fermentation system. The gas-liquid transport resistance can be overcome and the oxygen supply can be increased by adding hydrogen peroxide (H_2O_2) to the fermentation system. This paper shows that H_2O_2 can not only enhance the oxygen supply but also change the metabolism by inducing cytochrome P450, the key enzyme of α, ω-oxidation. When C. tropicalis was cultivated in a 3-liter bioreactor using the combination of aeration and hydrogen peroxide feeding, the DCA yield increased about 10% except at the beginning of H_2O_2 feeding. The experiments showed that the maximum activities of P450 could be induced at 2 mmol·L -1 H_2O_2. By adding H_2O_2, the DCA yield in a 22-liter bioreactor was increased 25.3% to 153.9 g/L.

A nanoplatform with oxygen self-supplying and heat-sensitizing capabilities enhances the efficacy of photodynamic therapy in eradicating multidrug-resistant biofilms

Bacterial biofilms,especially those caused by multidrug-resistant bacteria,have emerged as one of the greatest dangers to global public health.The acceleration of antimicrobial resistance to conventional an-tibiotics and the severe lack of new drugs necessitates the development of novel agents for biofilm eradication.Photodynamic therapy(PDT)is a promising non-antibiotic method for treating bacterial infections.However,its application in biofilm eradication is hampered by the hypoxic microenvironment of biofilms and the physical protection of extracellular polymeric substances.In this study,we develop a composite nanoplatform with oxygen(O_(2))self-supplying and heat-sensitizing capabilities to improve the PDT efficacy against biofilms.CaO_(2)/ICG@PDA nanoparticles(CIP NPs)are fabricated by combining calcium peroxide(CaO_(2))with the photosensitizer indocyanine green(ICG)via electrostatic interactions,followed by coating with polydopamine(PDA).The CIP NPs can gradually generate O_(2)in response to the acidic microenvironment of the biofilm,thereby alleviating its hypoxic state.Under near-infrared(NIR)irradiation,the nanoplatform converts O_(2)into a significant amount of singlet oxygen(^(1)O_(2))and heat to eradicate biofilm.The generated heat enhances the release of O_(2),accelerates the generation of^(1)O_(2)in PDT,increases cell membrane permeability,and increases bacterial sensitivity to^(1)O_(2).This nanoplatform significantly improves the efficacy of PDT in eradicating biofilm-dwelling bacteria without fostering drug resistance.Experiments on biofilm eradication demonstrate that this nanoplatform can eradicate over 99.9999%of methicillin-resistant Staphylococcus aureus(MRSA)biofilms under 5-min NIR irradiation.Notably,these integrated advantages enable the system to promote the healing of MRSA biofilm-infected wounds with negligible toxicity in vivo,indicating great promise for overcoming the obstacles associated with bacterial biofilm eradication.

Causes and detection of coalfield fires, control techniques, and heat energy recovery: A review

Coalfield fires are considered a global crisis that contributes significantly to environmental destruction and loss of coal resources and poses a serious threat to human safety and health. In this paper, research related to the initiation, development, and evolution of coalfield fires is reviewed. The existing detection and control techniques of coalfield fires are also reviewed. Traditional firefighting is associated with waste of resources, potential risks of recrudescence, potential safety hazards, extensive and expensive engineering works, and power shortages. Recently,coalfield fires have been recognized as having significant potential for energy conservation and heat energy recovery. Thermoelectric power generation is regarded as a suitable technology for the utilization of heat from coalfield fires. The extraction of heat from coalfield fires can also control coalfield fires and prevent reignition leading to combustion. Technologies for absorbing heat from burning coal and overlying rocks are also analyzed. In addition, the control mode of "three-region linkage" is proposed to improve firefighting efficiency. Integrating heat energy recovery with firefighting is an innovative method to control coalfield fires.

Study on the Establishment of a Rat Model for Transfusion-related Acute Lung Injury with Coronary Heart Disease and its Oxygen Balance

Objective:To establish a rat model of transfusion-related acute lung injury(TRALI)with coronary heart disease(CHD),and to analyze the safety of blood transfusion through oxygen balance.Methods:Forty-five 10-day-old male Wistar rats were purchased,and 35 of them were fed with high-fat diet to establish coronary heart disease rat models,and then 20 of them were selected to establish rat models of transfusion-related acute lung injury with coronary heart disease(model group,10 rats),positive acute lung injury group(positive group,5 rats)and negative acute lung injury group(negative group,5 rats),and the lung histomorphology,pathological score and wet/dry weight ratio were compared.Then,another 15 rats with coronary heart disease were selected and infused with mutant Hb,rHb1.1 and rHb2.0 with the same osmotic pressure through femoral vein catheterization,respectively,and were divided into mutant Hb group,rHb1.1 group and rHb2.0 group,with 5 rats in each group,and 5 healthy rats were combined as control group.The MAP,HR and blood gas values of mesenteric artery of rats were compared at 0,30,60 and 90 min after infusion.Results:(1)Rats in the model group and the positive group showed symptoms such as irregular and shallow breathing,increased oral and nasal secretions,and audible wheezing,which were consistent with the symptoms of acute lung injury.Comparison of lung histological score and lung tissue wet/dry ratio in three groups:There was no significant difference in lung histological score and lung tissue wet/dry ratio(P>0.05),but they were higher than those in the negative group(P<0.05).(2)During hemoglobin infusion,the MAP of mutant Hb group,rHb1.1 group and rHb2.0 group was higher than that of the control group,while the pH and PaCO2were lower than those of the control group(P<0.05),and there was no significant difference in QSMA(P>0.05).In the mutant Hb group,MAP returned to normal at 30-60 min after infusion(P>0.05),but MAP increased again at 90 min after infusion(P<0.05),and QSMA increased significantly at 60 min after transfusion(P<0.05).The pH value was lower than the normal value and the PaCO2was higher than the normal value within 90 min of infusion(P<0.05),and the HCO3-level returned to normal after 30 min of infusion(P>0.05).In rHb 1.1 group,MAP returned to normal,QSMA remained at normal level(P>0.05),and pH,PaCO2and HCO3-returned to normal after 60 min of infusion(P>0.05);In rHb 2.0 group,the levels of MAP,pH,PaCO2and HCO3-returned to normal after 30 min of infusion(P>0.05),and QSMA remained normal during infusion(P>0.05).Conclusion:The rat model of transfusion-relatted acute lung injury with coronary heart disease can be successfully established by injecting LPS into the rat model of coronary heart disease,and the infusion of recombinant hemoglobin can improve the balance of blood supply in rats,in which the infusion of rHb2.0 can better correct the metabolic acidosis.

High Efficient Blowing Technique for Large and Medium Converters

The high efficient blowing technique includes increasing oxygen supply intensity and optimizing slag forming. The oxygen supply intensity on 300 t converters of No. 1 steelmaking shop at Baosteel reaches 3.83 m^3/（t · min）, and at Taiyuan Steel, Lianyuan Steel, Pingxiang Steel and other steel plants, the oxygen supply intensity on medium converters is in the range of 4.0--4.4m^3/（t · min）. The productivity of converter can be increased by 8% -- 15% with adopting this technique. The whole technique, including design and manufacture of lance nozzle with reasonable pacnolontenue of outlets, technique of oxygen supply and slag forming, has been developed by CISRI to meet the need of technique transfer.