Production of gamma-aminobutyric acid by Lactobacillus brevis NCL912 using fed-batch fermentation

<p>Abstract</p> <p>Background</p> <p>Gamma-aminobutyric acid is a major inhibitory neurotransmitter in mammalian brains, and has several well-known physiological functions. Lactic acid bacteria possess special physiological activities and are generally regarded as safe. Therefore, using lactic acid bacteria as cell factories for gamma-aminobutyric acid production is a fascinating project and opens up a vast range of prospects for making use of GABA and LAB. We previously screened a high GABA-producer <it>Lactobacillus brevis </it>NCL912 and optimized its fermentation medium composition. The results indicated that the strain showed potential in large-scale fermentation for the production of gamma-aminobutyric acid. To increase the yielding of GABA, further study on the fermentation process is needed before the industrial application in the future. In this article we investigated the impacts of pyridoxal-5'-phosphate, pH, temperature and initial glutamate concentration on gamma-aminobutyric acid production by <it>Lactobacillus brevis </it>NCL912 in flask cultures. According to the data obtained in the above, a simple and effective fed-batch fermentation method was developed to highly efficiently convert glutamate to gamma-aminobutyric acid.</p> <p>Results</p> <p>Pyridoxal-5'-phosphate did not affect the cell growth and gamma-aminobutyric acid production of <it>Lb. brevis </it>NCL912. Temperature, pH and initial glutamate concentration had significant effects on the cell growth and gamma-aminobutyric acid production of <it>Lb. brevis </it>NCL912. The optimal temperature, pH and initial glutamate concentration were 30-35°C, 5.0 and 250-500 mM. In the following fed-batch fermentations, temperature, pH and initial glutamate concentration were fixed as 32°C, 5.0 and 400 mM. 280.70 g (1.5 mol) and 224.56 g (1.2 mol) glutamate were supplemented into the bioreactor at 12 h and 24 h, respectively. Under the selected fermentation conditions, gamma-aminobutyric acid was rapidly produced at the first 36 h and almost not produced after then. The gamma-aminobutyric acid concentration reached 1005.81 ± 47.88 mM, and the residual glucose and glutamate were 15.28 ± 0.51 g L^-1and 134.45 ± 24.22 mM at 48 h.</p> <p>Conclusions</p> <p>A simple and effective fed-batch fermentation method was developed for <it>Lb. brevis </it>NCL912 to produce gamma-aminobutyric acid. The results reveal that <it>Lb. brevis </it>NCL912 exhibits a great application potential in large-scale fermentation for the production of gamma-aminobutyric acid.</p

Electrically tunable Gilbert damping in van der Waals heterostructures of two-dimensional ferromagnetic metals and ferroelectrics

Tuning the Gilbert damping of ferromagnetic (FM) metals via a nonvolatile way is of importance to exploit and design next-generation novel spintronic devices. Through systematical first-principles calculations, we study the magnetic properties of the van der Waals heterostructure of two-dimensional FM metal CrTe2 and ferroelectric (FE) In2Te3 monolayers. The ferromagnetism of CrTe2 is maintained in CrTe2/In2Te3 and its magnetic easy axis can be switched from in-plane to out-of-plane by reversing the FE polarization of In2Te3. Excitingly, we find that the Gilbert damping of CrTe2 is tunable when the FE polarization of In2Te3 is reversed from upward to downward. By analyzing the k-dependent contributions to the Gilbert damping, we unravel that such tunability results from the changed intersections between the bands of CrTe2 and Fermi level on the reversal of the FE polarizations of In2Te3 in CrTe2/In2Te3. Our work provides an appealing way to electrically tailor Gilbert dampings of two-dimensional FM metals by contacting them with ferroelectrics.Comment: 4 Figures, accepted by Applied Physics Letter

Zonal Patterns of Delta C-13, Delta N-15 and Po-210 In the Tropical and Subtropical North Pacific

Nitrogen fixation process may supply a significant fraction of bioavailable nitrogen to surface waters, increase the oceanic sequestration of atmospheric CO2, and alter the distribution of geochemical parameters. We report a zonal pattern of delta N-15 and delta C-13 in particulate organic matter (POM), and ratios of particulate Po-210 to dissolved Po-210 along a transect through the subtropical and tropical North Pacific. Both N-15 and Po-210 signals indicated an enhanced N-2 fixation in the northwestern subtropical North Pacific. The eastward decrease of N-2 fixation along this transect testified the role of aeolian Fe and P in controlling marine N-2 fixation. Associated with the zonal variations of N-15 and Po-210, the delta C-13 of suspended POM increased eastward, reflecting the decrease of anthropogenic CO2 concentration in surface seawater from west to east in the study area. Our results highlight the need to examine more closely the mechanisms of possible longitudinal variation in N-2 fixation in the ocean and the role of aeolian Fe and P in controlling marine N-2 fixation and anthropogenic CO2

Hot isostatic pressing of in-situ TiB/Ti-6Al-4V composites with novel reinforcement architecture, enhanced hardness and elevated tribological properties

In this study, titanium borides reinforced Ti-6Al-4V composites have been successfully prepared by hot isostatic pressing (HIPing). The microstructure of the as-fabricated samples was investigated using X-ray diffraction technique, secondary electron microscopy and electron backscatter diffraction and the mechanical properties evaluated through micro-hardness and wear resistance measurements together with nano-indentation. It was found that during HIPing the additive particles TiB2 have transformed into TiB needles which tend to decorate at prior particle boundaries of the consolidated powder particles to form a network structure. Under the same HIPing condition, the needles became increasingly coarser and agglomerated with increased addition of TiB2. The micro-hardness of the synthesized materials increased with increased volume fraction of TiB. Nano-indentation measurement demonstrates that the TiB network structure shows much higher nanohardness than the surrounding matrix regions. The friction coefficient of the synthesized composites decreased continuously with increased volume fraction of TiB, indicating improved wear resistance. High resolution transmission electron microscopy analysis on wear debris revealed the formation of a series of oxides suggesting that chemical reaction between alloy elements and oxygen in air may have happened. It is thus believed that the wearing of the current samples is a result of both friction and chemical reaction

Particle dynamics revealed by 210Po/210Pb disequilibria around Prydz Bay, the Southern Ocean in summer

Seawater samples were collected around Prydz Bay in summer of 2014, dissolved and particulate 210Po and 210Pb were measured to reveal the disequilibrium characteristics and particle dynamics. Our results show that the distribution of 210Po and 210Po/210Pb activity ratio in the upper water is mainly affected by biological absorption or particle adsorption. An abnormal excess of 210Po relative to 210Pb was observed in the surface water at stations P1-2 and P2-2, which is likely to be the horizontal transport of water mass with high DPo/DPb)A.R. and TPo/TPb)A.R.. In this study, the removal of particulate 210Po is mainly controlled by the scavenging of dissolved 210Po and the two have a linear positive correlation with the salinity, a negative linear correlation with the content of dissolved oxygen and a reciprocal relationship with the content of POC. The export flux of POC at 100 m is estimated to be 1.8–4.4 mmol·m−2·d−1 (avg. 2.9 mmol·m−2·d−1) based on 210Po/210Pb disequilibria, with the highest value in the shelf, which is consistent with the distribution of biological productivity

Enhanced but highly variable bioturbation around seamounts in the northwest Pacific

Abstract(#br)Seamounts are a unique ecosystem in marine environment, but the relevant understanding is limited. In this study, sedimentation and bioturbation around the Pako Guyot of Magellan, and the Lamont, Scripps, Arnold, and Pot Guyots of Marcus-Wake seamounts in the northwest Pacific were evaluated using 230 Th ex and 210 Pb ex as tracers. Our results showed that the linear sedimentation rate and the mass accumulation rate ranged from 0.12 to 2.50 mm/ka and from 0.06 to 1.14 kg/m 2 /ka with averages of 1.27 ± 0.80 mm/ka and 0.49 ± 0.30 kg/m 2 /ka respectively. The accumulation flux of organic carbon in surface sediments was estimated to be 0.10-4.52 gC/m 2 /ka. The bioturbation coefficients ranged from 1.01 to 27.1 cm 2 /a with an average of 10.8 ± 9.2 cm 2 /a, which is higher than those in abyssal sediments or predicted by traditional empirical equations. The enhanced bioturbation supports the view that seamounts are hotspots for pelagic benthic organisms. The bioturbation intensity showed a great variability with the maximum around 40 km away from the edge of seamount summit. The bioturbation coefficient correlated positively with sedimentation rate and accumulation flux of organic carbon in surface sediments, indicating that the supply of organic matter is a main driving force for enhanced bioturbation around the seamounts. The increase in sedimentary organic matter promotes the activities of benthic organisms. More research is needed to gain a deep understanding of bioturbation in seamounts in the context of future climate change

Ultraviolet Light Responsive N‐Nitroso Polymers for Antibacterial Nitric Oxide Delivery

AbstractThis study investigates the incorporation of active secondary amine moieties into the polymer backbone by co‐polymerizing 2,4,6‐tris(chloromethyl)‐mesitylene (TCM) with three diamines, namely 1,4‐diaminobutane (DAB), m‐phenylenediamine (MPD), and p‐phenylenediamine (PPD). This process results in the stabilisation of the amine moieties and the subsequently introduced nitroso groups. Charging bioactive nitric oxide (NO) into the polymers is accomplished by converting the amine moieties into N‐nitroso groups. The ability of the polymers to store and release NO depends on their structures, particularly the amounts of incorporated active secondary amines. With grafting photosensitive N‐nitroso groups into the polymers, the derived NO@polymers exhibit photoresponsivity. NO release is completely regulated by adjusting UV light irradiation. These resulting polymeric NO donors demonstrate remarkable bactericidal and bacteriostatic activity, effectively eradicating E. coli bacteria and inhibiting their growth. The findings from this study hold promising implications for combining NO delivery with phototherapy in various medical applications.This article is protected by copyright. All rights reserve

Transcutaneous Electrical Acupoint Stimulation Improves the Postoperative Quality of Recovery and Analgesia after Gynecological Laparoscopic Surgery: A Randomized Controlled Trial

Background. We conducted this prospective, randomized, double-blind, placebo-controlled study to evaluate the effects of transcutaneous electric acupoint stimulation (TEAS) on the quality of recovery (QoR) and postoperative analgesia after gynecological laparoscopic surgery. Methods. 74 American Society of Anesthesiologists physical status (ASA) I or II patients undergoing gynecological laparoscopic surgery were randomly allocated to TEAS or control groups. The primary outcome was the quality of recovery, which was assessed on the day before surgery and 24 h after surgery using a 40-item questionnaire. Secondary outcomes included postoperative pain scores, the incidence of postoperative nausea and vomiting (PONV), duration of postanesthesia care unit (PACU) stay, and patient’s satisfaction. Results. The TEAS group had higher QoR scores than control group upon 24 h after surgery (177 versus 165; P<0.001). Compared with the control group, postoperative pain scores and the cumulative number of opioids administered were lower in the TEAS group patients (P=0.04). TEAS reduced the incidence of PONV and dizziness, as well as duration of PACU stay. Simultaneously, the patient’s satisfaction scores were higher in the TEAS group (P=0.002). Conclusion. Preoperative TEAS enhances QoR, improves postoperative analgesia and patient’s satisfaction, alleviates postoperative side effects, and accelerates discharge after general anesthesia for gynecological laparoscopic surgery

N2 fixation rate and diazotroph community structure in the western tropical North Pacific Ocean

Abstract(#br)In the present study, we report N2 fixation rate (15N isotope tracer assay) and the diazotroph community structure (using the molecular method) in the western tropical North Pacific Ocean (WTNP) (13°–20°N, 120°–160°E). Our independent evidence on the basis of both in situ N2 fixation activity and diazotroph community structure showed the dominance of unicellular N2 fixation over majority of the WTNP surface waters during the sampling periods. Moreover, a shift in the diazotrophic composition from unicellular cyanobacteria group B-dominated to Trichodesmium spp.-dominated toward the western boundary current (Kuroshio) was also observed in 2013. We hypothesize that nutrient availability may have played a major role in regulating the biogeography..

Secondary Production of Gaseous Nitrated Phenols in Polluted Urban Environments

Nitrated phenols (NPs) are important atmospheric pollutants that affect air quality, radiation, and health. The recent development of the time-of-flight chemical ionization mass spectrometer (ToF-CIMS) allows quantitative online measurements of NPs for a better understanding of their sources and environmental impacts. Herein, we deployed nitrate ions as reagent ions in the ToF-CIMS and quantified six classes of gaseous NPs in Beijing. The concentrations of NPs are in the range of 1 to 520 ng m(-3). Nitrophenol (NPh) has the greatest mean concentration. Dinitrophenol (DNP) shows the greatest haze-to-clean concentration ratio, which may be associated with aqueous production. The high concentrations and distinct diurnal profiles of NPs indicate a strong secondary formation to overweigh losses, driven by high emissions of precursors, strong oxidative capacity, and high NOx levels. The budget analysis on the basis of our measurements and box-model calculations suggest a minor role of the photolysis of NPs (Peer reviewe