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1.
Effect of Cultivation Parameters on Fermentation and Hydrogen Production in the Phylum Thermotogae.
Lanzilli, M, Esercizio, N, Vastano, M, Xu, Z, Nuzzo, G, Gallo, C, Manzo, E, Fontana, A, d'Ippolito, G
International journal of molecular sciences. 2020;(1)
Abstract
The phylum Thermotogae is composed of a single class (Thermotogae), 4 orders (Thermotogales, Kosmotogales, Petrotogales, Mesoaciditogales), 5 families (Thermatogaceae, Fervidobacteriaceae, Kosmotogaceae, Petrotogaceae, Mesoaciditogaceae), and 13 genera. They have been isolated from extremely hot environments whose characteristics are reflected in the metabolic and phenotypic properties of the Thermotogae species. The metabolic versatility of Thermotogae members leads to a pool of high value-added products with application potentials in many industry fields. The low risk of contamination associated with their extreme culture conditions has made most species of the phylum attractive candidates in biotechnological processes. Almost all members of the phylum, especially those in the order Thermotogales, can produce bio-hydrogen from a variety of simple and complex sugars with yields close to the theoretical Thauer limit of 4 mol H2/mol consumed glucose. Acetate, lactate, and L-alanine are the major organic end products. Thermotagae fermentation processes are influenced by various factors, such as hydrogen partial pressure, agitation, gas sparging, culture/headspace ratio, inoculum, pH, temperature, nitrogen sources, sulfur sources, inorganic compounds, metal ions, etc. Optimization of these parameters will help to fully unleash the biotechnological potentials of Thermotogae and promote their applications in industry. This article gives an overview of how these operational parameters could impact Thermotogae fermentation in terms of sugar consumption, hydrogen yields, and organic acids production.
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2.
A narrative review of hydrogen-oxygen mixture for medical purpose and the inhaler thereof.
Lin, HY, Lai, PC, Chen, WL
Medical gas research. 2020;(4):193-200
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Abstract
Recent development regarding mixture of H2 (concentration of ~66%) with O2 (concentration of ~34%) for medical purpose, such as treatment of coronavirus disease-19 (COVID-19) patients, is introduced. Furthermore, the design principles of a hydrogen inhaler which generates mixture of hydrogen (~66%) with oxygen (~34%) for medical purpose are proposed. With the installation of the liquid blocking module and flame arresters, the air pathway of the hydrogen inhaler is divided by multiple isolation zones to prevent any unexpected explosion propagating from one zone to the other. An integrated filtering/cycling module is utilized to purify the impurity, and cool down the temperature of the electrolytic module to reduce the risk of the explosion. Moreover, a nebulizer is provided to selectively atomize the water into vapor which is then mixed with the filtered hydrogen-oxygen mix gas, such that the static electricity of a substance hardly occurs to reduce the risk of the explosion. Furthermore, hydrogen concentration detector is installed to reduce the risk of hydrogen leakage. Result shows that the hydrogen inhaler implementing the aforesaid design rules could effectively inhibit the explosion, even ignition at the outset of the hydrogen inhaler which outputs hydrogen-oxygen gas (approximately 66% hydrogen: 34% oxygen).
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The hydrogen gas bio-based economy and the production of renewable building block chemicals, food and energy.
De Vrieze, J, Verbeeck, K, Pikaar, I, Boere, J, Van Wijk, A, Rabaey, K, Verstraete, W
New biotechnology. 2020;:12-18
Abstract
The carrying capacity of the planet is being exceeded, and there is an urgent need to bring forward revolutionary approaches, particularly in terms of energy supply, carbon emissions and nitrogen inputs into the biosphere. Hydrogen gas, generated by means of renewable energy through water electrolysis, can be a platform molecule to drive the future bioeconomy and electrification in the 21st century. The potential to use hydrogen gas in microbial metabolic processes is highly versatile, and this opens a broad range of opportunities for novel biotechnological developments and applications. A first approach concerns the central role of hydrogen gas in the production of bio-based building block chemicals using the methane route, thus, bypassing the inherent low economic value of methane towards higher-value products. Second, hydrogen gas can serve as a key carbon-neutral source to produce third-generation proteins, i.e. microbial protein for food applications, whilst simultaneously enabling carbon capture and nutrient recovery, directly at their point of emission. Combining both approaches to deal with the intermittent nature of renewable energy sources maximises the ability for efficient use of renewable resources.
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The odyssey of cobaloximes for catalytic H2 production and their recent revival with enzyme-inspired design.
Dolui, D, Khandelwal, S, Majumder, P, Dutta, A
Chemical communications (Cambridge, England). 2020;(59):8166-8181
Abstract
Cobaloxime complexes gained attention for their intrinsic ability of catalytic H2 production despite their initial emergence as a vitamin B12 model. The simple, robust, and synthetically manoeuvrable cobaloxime core represents a model catalyst molecule for the investigation of optimal conditions for both photo- and electrocatalytic H2 production catalytic assemblies. Cobaloxime is one of the rare catalysts that finds equal applications in the analysis of homogeneous and heterogeneous catalytic conditions. However, the poor aqueous solubility and long-term instability of cobaloximes have severely impeded their growth. Lately, interest in the cobaloxime-based catalysts has been resuscitated with the rational use of extended enzymatic features. This unique enzyme-inspired catalyst design strategy has instigated the formation of a new genre of cobaloxime molecules that exhibit enhanced photo- and electrocatalytic H2 evolution with improved aqueous and air stability.
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5.
Energy-converting hydrogenases: the link between H2 metabolism and energy conservation.
Schoelmerich, MC, Müller, V
Cellular and molecular life sciences : CMLS. 2020;(8):1461-1481
Abstract
The reversible interconversion of molecular hydrogen and protons is one of the most ancient microbial metabolic reactions and catalyzed by hydrogenases. A widespread yet largely enigmatic group comprises multisubunit [NiFe] hydrogenases, that directly couple H2 metabolism to the electrochemical ion gradient across the membranes of bacteria and of archaea. These complexes are collectively referred to as energy-converting hydrogenases (Ech), as they reversibly transform redox energy into physicochemical energy. Redox energy is typically provided by a low potential electron donor such as reduced ferredoxin to fuel H2 evolution and the establishment of a transmembrane electrochemical ion gradient ([Formula: see text]). The [Formula: see text] is then utilized by an ATP synthase for energy conservation by generating ATP. This review describes the modular structure/function of Ech complexes, focuses on insights into the energy-converting mechanisms, describes the evolutionary context and delves into the implications of relying on an Ech complex as respiratory enzyme for microbial metabolism.
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6.
The ambivalent role of water at the origins of life.
do Nascimento Vieira, A, Kleinermanns, K, Martin, WF, Preiner, M
FEBS letters. 2020;(17):2717-2733
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Abstract
Life as we know it would not exist without water. However, water molecules not only serve as a solvent and reactant but can also promote hydrolysis, which counteracts the formation of essential organic molecules. This conundrum constitutes one of the central issues in origin of life. Hydrolysis is an important part of energy metabolism for all living organisms but only because, inside cells, it is a controlled reaction. How could hydrolysis have been regulated under prebiotic settings? Lower water activities possibly provide an answer: geochemical sites with less free and more bound water can supply the necessary conditions for protometabolic reactions. Such conditions occur in serpentinising systems, hydrothermal sites that synthesise hydrogen gas via rock-water interactions. Here, we summarise the parallels between biotic and abiotic means of controlling hydrolysis in order to narrow the gap between biochemical and geochemical reactions and briefly outline how hydrolysis could even have played a constructive role at the origin of molecular self-organisation.
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Influence of Hydrogen Electron Donor, Alkaline pH, and High Nitrate Concentrations on Microbial Denitrification: A Review.
Albina, P, Durban, N, Bertron, A, Albrecht, A, Robinet, JC, Erable, B
International journal of molecular sciences. 2019;(20)
Abstract
Bacterial respiration of nitrate is a natural process of nitrate reduction, which has been industrialized to treat anthropic nitrate pollution. This process, also known as "microbial denitrification", is widely documented from the fundamental and engineering points of view for the enhancement of the removal of nitrate in wastewater. For this purpose, experiments are generally conducted with heterotrophic microbial metabolism, neutral pH and moderate nitrate concentrations (<50 mM). The present review focuses on a different approach as it aims to understand the effects of hydrogenotrophy, alkaline pH and high nitrate concentration on microbial denitrification. Hydrogen has a high energy content but its low solubility, 0.74 mM (1 atm, 30 °C), in aqueous medium limits its bioavailability, putting it at a kinetic disadvantage compared to more soluble organic compounds. For most bacteria, the optimal pH varies between 7.5 and 9.5. Outside this range, denitrification is slowed down and nitrite (NO2-) accumulates. Some alkaliphilic bacteria are able to express denitrifying activity at pH levels close to 12 thanks to specific adaptation and resistance mechanisms detailed in this manuscript, and some bacterial populations support nitrate concentrations in the range of several hundred mM to 1 M. A high concentration of nitrate generally leads to an accumulation of nitrite. Nitrite accumulation can inhibit bacterial activity and may be a cause of cell death.
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How to make the reducing power of H2 available for in vivo biosyntheses and biotransformations.
Lauterbach, L, Lenz, O
Current opinion in chemical biology. 2019;:91-96
Abstract
Solar-driven electrolysis enables sustainable production of molecular hydrogen (H2), which represents a cheap and carbon-free reductant. Knallgas bacteria like Ralstonia eutropha are able to split H2 to supply energy in form of ATP and NADH, which can be subsequently used to power reactions of interest. R. eutropha employs the Calvin-Benson-Bassham cycle for the fixation of CO2, which is considered as an abundant and non-competing raw material. In this article, we summarize state-of-the-art approaches for H2-driven biosyntheses using engineered R. eutropha. Furthermore, we describe strategies for synthetic H2-driven NADH recycling. Major challenges for technical application and future perspectives are discussed.
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Biological hydrogen production: molecular and electrolytic perspectives.
Mahidhara, G, Burrow, H, Sasikala, C, Ramana, CV
World journal of microbiology & biotechnology. 2019;(8):116
Abstract
Exploration of renewable energy sources is an imperative task in order to replace fossil fuels and to diminish atmospheric pollution. Hydrogen is considered one of the most promising fuels for the future and implores further investigation to find eco-friendly ways toward viable production. Expansive processes like electrolysis and fossil fuels are currently being used to produce hydrogen. Biological hydrogen production (BHP) displays recyclable and economical traits, and is thus imperative for hydrogen economy. Three basic modes of BHP were investigated, including bio photolysis, photo fermentation and dark fermentation. Photosynthetic microorganisms could readily serve as powerhouses to successively produce this type of energy. Cyanobacteria, blue green algae (bio photolysis) and some purple non-sulfur bacteria (Photo fermentation) utilize solar energy and produce hydrogen during their metabolic processes. Ionic species, including hydrogen (H+) and electrons (e-) are combined into hydrogen gas (H2), with the use of special enzymes called hydrogenases in the case of bio photolysis, and nitrogenases catalyze the formation of hydrogen in the case of photo fermentation. Nevertheless, oxygen sensitivity of these enzymes is a drawback for bio photolysis and photo fermentation, whereas, the amount of hydrogen per unit substrate produced appears insufficient for dark fermentation. This review focuses on innovative advances in the bioprocess research, genetic engineering and bioprocess technologies such as microbial fuel cell technology, in developing bio hydrogen production.
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10.
Advances in research on treatment of heart failure with nitrosyl hydrogen.
Guo, Y, Xu, J, Wu, L, Deng, Y, Wang, J, An, J
Heart failure reviews. 2019;(6):941-948
Abstract
Heart failure is the end stage of various heart diseases such as ischemic heart disease, dilated cardiomyopathy, valvular heart disease, congenital heart disease, and hypertensive myocardial damage. It is characterized by a decrease in myocardial contractility, but there is currently no ideal treatment. Nitroxyl hydrogen (HNO) is considered to be a protonated form of NO. It has special chemical properties compared to other nitrogen oxides. In the body of organisms, HNO can participate in all aspects of the occurrence and development of heart failure (HF) and react with some proteins closely related to cardiac activity, changing its spatial structure and exerting cardioprotective effects. In recent years, studies have shown that HNO can inhibit cardiomyocyte hypertrophy, reduce inflammation, enhance myocardial contractility, dilate coronary arteries as well as peripheral blood vessels in early heart failure, and protect the heart against heart failure. This paper, combined with the latest research results at home and abroad, clarifies that nitrosyl hydrogen exerts cardioprotective effects through various processes that occur in the development of heart failure.