Improved production of biohydrogen in light-powered Escherichia coli by co-expression of proteorhodopsin and heterologous hydrogenase

<p>Abstract</p> <p>Background</p> <p>Solar energy is the ultimate energy source on the Earth. The conversion of solar energy into fuels and energy sources can be an ideal solution to address energy problems. The recent discovery of proteorhodopsin in uncultured marine γ-proteobacteria has made it possible to construct recombinant <it>Escherichia coli </it>with the function of light-driven proton pumps. Protons that translocate across membranes by proteorhodopsin generate a proton motive force for ATP synthesis by ATPase. Excess protons can also be substrates for hydrogen (H₂) production by hydrogenase in the periplasmic space. In the present work, we investigated the effect of the co-expression of proteorhodopsin and hydrogenase on H₂production yield under light conditions.</p> <p>Results</p> <p>Recombinant <it>E. coli </it>BL21(DE3) co-expressing proteorhodopsin and [NiFe]-hydrogenase from <it>Hydrogenovibrio marinus </it>produced ~1.3-fold more H₂in the presence of exogenous retinal than in the absence of retinal under light conditions (70 μmole photon/(m²·s)). We also observed the synergistic effect of proteorhodopsin with endogenous retinal on H₂production (~1.3-fold more) with a dual plasmid system compared to the strain with a single plasmid for the sole expression of hydrogenase. The increase of light intensity from 70 to 130 μmole photon/(m²·s) led to an increase (~1.8-fold) in H₂production from 287.3 to 525.7 mL H₂/L-culture in the culture of recombinant <it>E. coli </it>co-expressing hydrogenase and proteorhodopsin in conjunction with endogenous retinal. The conversion efficiency of light energy to H₂achieved in this study was ~3.4%.</p> <p>Conclusion</p> <p>Here, we report for the first time the potential application of proteorhodopsin for the production of biohydrogen, a promising alternative fuel. We showed that H₂production was enhanced by the co-expression of proteorhodopsin and [NiFe]-hydrogenase in recombinant <it>E. coli </it>BL21(DE3) in a light intensity-dependent manner. These results demonstrate that <it>E. coli </it>can be applied as light-powered cell factories for biohydrogen production by introducing proteorhodopsin.</p

Production of biohydrogen by recombinant expression of [NiFe]-hydrogenase 1 in Escherichia coli

<p>Abstract</p> <p>Background</p> <p>Hydrogenases catalyze reversible reaction between hydrogen (H₂) and proton. Inactivation of hydrogenase by exposure to oxygen is a critical limitation in biohydrogen production since strict anaerobic conditions are required. While [FeFe]-hydrogenases are irreversibly inactivated by oxygen, it was known that [NiFe]-hydrogenases are generally more tolerant to oxygen. The physiological function of [NiFe]-hydrogenase 1 is still ambiguous. We herein investigated the H₂production potential of [NiFe]-hydrogenase 1 of <it>Escherichia coli in vivo </it>and <it>in vitro</it>. The <it>hya</it>A and <it>hya</it>B genes corresponding to the small and large subunits of [NiFe]-hydrogenase 1 core enzyme, respectively, were expressed in BL21, an <it>E. coli </it>strain without H₂producing ability.</p> <p>Results</p> <p>Recombinant BL21 expressing [NiFe]-hydrogenase 1 actively produced H₂(12.5 mL H₂/(h·L) in 400 mL glucose minimal medium under micro-aerobic condition, whereas the wild type BL21 did not produce H₂even when formate was added as substrate for formate hydrogenlyase (FHL) pathway. The majority of recombinant protein was produced as an insoluble form, with translocation of a small fraction to the membrane. However, the membrane fraction displayed high activity (~65% of total cell fraction), based on unit protein mass. Supplement of nickel and iron to media showed these metals contribute essentially to the function of [NiFe]-hydrogenase 1 as components of catalytic site. In addition, purified <it>E. coli </it>[NiFe]-hydrogenase 1 using his₆-tag displayed oxygen-tolerant activity of ~12 nmol H₂/(min·mg protein) under a normal aeration environment, compared to [FeFe]-hydrogenase, which remains inactive under this condition.</p> <p>Conclusions</p> <p>This is the first report on physiological function of <it>E. coli </it>[NiFe]-hydrogenase 1 for H₂production. We found that [NiFe]-hydrogenase 1 has H₂production ability even under the existence of oxygen. This oxygen-tolerant property is a significant advantage because it is not necessary to protect the H₂production process from oxygen. Therefore, we propose that [NiFe]-hydrogenase can be successfully applied as an efficient biohydrogen production tool under micro-aerobic conditions.</p

Control of nacre biomineralization by Pif80 in pearl oyster

Molluscan nacre is a fascinating biomineral consisting of a highly organized calcium carbonate composite that provides unique fracture toughness and an iridescent color. Organisms elaborately control biomineralization using organic macromolecules. We propose the involvement of the matrix protein Pif80 from the pearl oyster Pinctada fucata in the development of the inorganic phase during nacre biomineralization, based on experiments using the recombinant form of Pif80. Through interactions with calcium ions, Pif80 participates in the formation of polymer-induced liquid precursor-like amorphous calcium carbonate granules and stabilizes these granules by forming calcium ion-induced coacervates. At the calcification site, the disruption of Pif80 coacervates destabilizes the amorphous mineral precursors, resulting in the growth of a crystalline structure. The redissolved Pif80 controls the growth of aragonite on the polysaccharide substrate, which contributes to the formation of polygonal tablet structure of nacre. Our findings provide insight into the use of organic macromolecules by living organisms in biomineralization.117Ysciescopu

Electric field control of nonvolatile four-state magnetization at room temperature

We find the realization of large converse magnetoelectric (ME) effects at room temperature in a multiferroic hexaferrite Ba$_{0.52}$Sr$_{2.48}$Co$_{2}$Fe$_{24}$O$_{41}$ single crystal, in which rapid change of electric polarization in low magnetic fields (about 5 mT) is coined to a large ME susceptibility of 3200 ps/m. The modulation of magnetization then reaches up to 0.62 $\mu$$_{B}$/f.u. in an electric field of 1.14 MV/m. We find further that four ME states induced by different ME poling exhibit unique, nonvolatile magnetization versus electric field curves, which can be approximately described by an effective free energy with a distinct set of ME coefficients

A Novel Technique of Morcellation Using a Pneumovesicum After Holmium Laser Enucleation of the Prostate in Complicated Situations: Our Initial Experience and Tips

Purpose To describe our initial experience with a novel method of adenoma retrieval using a pneumovesicum (PNV) after Holmium laser enucleation of the prostate (HoLEP). Methods From January 2016 to April 2018, a total of 93 consecutive patients treated with HoLEP were enrolled in this study. For tissue morcellation, we used the PNV morcellation technique for an initial series of 21 patients and the conventional technique (Lumenis VersaCut) for a consecutive series of 72 patients. We compared efficiency and safety between the novel technique and the traditional technique. Subgroup analysis was performed to assess the effectiveness of the current technique in the large prostate (>70 mL). Results There were significant differences in mean age and prostate volume between the 2 groups. However, there were no significant differences in the baseline characteristics and preoperative parameters in the subgroup analysis of large prostates (>70 mL). The mean morcellation efficiency was higher (8.50±1.94 minutes vs. 1.76±0.45 minutes, P<0.05) and the time of morcellation (7.81±1.25 minutes vs. 34.04±11.14 minutes, P<0.05) was shorter in the PNV group. Moreover, there were no significant differences between groups in hospitalization period (2.62±1.10 days vs. 2.90±1.26 days, P=0.852) and any other postoperative events, including recatheterization, reoperation, clot retention, and urethral stricture (P-value range, 0.194–0.447). In the PNV group, there were some cases of procedure-related complications, including postoperative extravesical leakage (5th case), clot retention (8th case), and recatheterization (9th case). Conclusions This method has a higher tissue retrieval efficacy, with the advantage of excellent visibility compared to conventional morcellation. The current method can be applied when a transurethral morcellator is out of order or cannot be used

Long-term follow-up of Fanconi anemia: clinical manifestation and treatment outcome

PurposeThe aim of this study was to characterize Korean patients with Fanconi anemia (FA), which is a rare but very challenging genetic disease.MethodsThe medical records of 12 FA patients diagnosed at Chonnam National University Hospital from 1991 to 2012 were retrospectively reviewed.ResultsThe median age at diagnosis was 6.2 years. All patients showed evidence of marrow failure and one or more physical stigmata. Chromosome breakage tests were positive in 9 out of 11 available patients. The median follow-up duration was 69.5 months. The Kaplan-Meier (KM) survival of all patients was 83.3% at 10 years and 34.7% at 20 years, respectively. Seven patients underwent 9 stem cell transplantations (SCTs). Among them, 5 were alive by the end of the study. Ten-year KM survival after SCT was 71.4% with a median follow-up of 3.4 years. All 5 patients treated with supportive treatment alone died of infection or progression at the median age of 13.5 years, except for one with short follow-up duration. Acute leukemia developed in 2 patients at 15.4 and 18.1 years of age. Among 6 patients who are still alive, 3 had short stature and 1 developed insulin-dependent diabetes mellitus.ConclusionWe provide information on the long-term outcomes of FA patients in Korea. A nation-wide FA registry that includes information of the genotypes of Korean patients is required to further characterize ethnic differences and provide the best standard of care for FA patients

Development of a Novel Intraoperative Neuromonitoring System Using a Surface Pressure Sensor to Detect Muscle Movement: A Rabbit Model Study

Objectives False-negative or false-positive responses in intraoperative neuromonitoring (IONM) using electromyography (EMG) in thyroid surgery pose a challenge. Therefore, we developed a novel IONM system that uses a surface pressure sensor instead of EMG to detect muscle twitching. This study aimed to investigate the feasibility and safety of a new IONM system using a piezo-electric surface pressure sensor in an experimental animal model. Methods We developed the surface pressure sensor by modifying a commercial piezo-electric sensor. We evaluated the stimulus thresholds to detect muscle movement, as well as the amplitude and latency of the EMG and surface pressure sensor in six sciatic nerves of three rabbits, according to the stimulus intensity. Results The surface pressure sensor detected the muscle movements in response to a 0.1 mA stimulation of all six sciatic nerves. There were no differences in the thresholds of stimulus intensity between the surface pressure sensor and EMG recordings to detect muscle movements. Conclusion It is possible to measure the change in surface pressure by using a piezo-electric surface pressure sensor instead of EMG to detect muscle movement induced by nerve stimulation. The application of IONM using a piezo-electric surface pressure sensor during surgery is noninvasive, safe, and feasible. Measuring muscle twitching to identify the state of the nerves using the novel IONM system can be an alternative to recording of EMG responses

Point prevalence and epidemiological characteristics of chronic cough in the general adult population: The Korean National Health and Nutrition Examination Survey 2010-2012

© 2017 the Author(s). Cough is frequently self-limiting, but may persist longer in certain individuals. Most of previous studies on the epidemiology of chronic cough have only measured period prevalence, and thus have afforded limited information on the burden and natural course. We aimed to investigate the epidemiology of chronic cough by using a point prevalence measure in a large-scale general population. We analyzed cross-sectional data collected from 18,071 adults who participated in the Korean National Health and Nutrition Examination Survey 2010-2012. Presence and duration of current cough was ascertained by structured questionnaires, and cough was classified into acute

Incidence of Hypertension in Korea: 5-Year Follow-up Study

Limited data are available about the incidence of hypertension over the 5-yr in non-hypertensive subjects. The study subjects were 1,806 subjects enrolled in a rural area of Daegu, Korea for a cohort study from August to November 2003. Of them, 1,287 (71.3%) individuals had another examination 5 yr later. To estimate the incidence of hypertension, 730 non-hypertensive individuals (265 males; mean age = 56.6 ± 11.1 yr-old) at baseline examination were analyzed in this study. Hypertension was defined as either a new diagnosis of hypertension or self-reports of newly initiated antihypertensive treatment; prehypertension was if the systolic blood pressure was 120-139 mmHg and/or diastolic blood pressure was 80-89 mmHg. During the 5-yr follow-up, 195 (26.7%) non-hypertensive individuals developed incident hypertension. The age-adjusted 5-yr incidence rates of hypertension were 22.9% (95% confidence interval [CI] = 19.9-29.0) in overall subjects, 22.2% (95% CI = 17.2-27.2) in men, and 24.3% (95% CI = 20.4-28.2) in women. The incidence rates of hypertension significantly increased with age. In the multivariate analysis, prehypertension (Odds ratio [OR] 2.25; P < 0.001) and older age (OR 2.26; P = 0.010) were independent predictors for incident hypertension. In this rapidly aging society, population-based preventive approach to decrease blood pressure, particularly in subjects with prehypertension, is needed to reduce hypertension