Hydrogen production from Biological organisms as well as from electrochemical or thermal process which is helpful for transportation.Advantage: No emission of Green House effect
Biohydrogen may produced by steam reforming of methane (biogas) produced by anaerobic digestion of organic waste. In the latter process, natural gas and steam react to produce hydrogen and carbon dioxide.
These slides use concepts from my (Jeff Funk) course entitled analyzing hi-tech opportunities to examine the increasing economic feasibility of algae biofuels. Algae can be grown in places where traditional crops cannot be grown and it consumes carbon dioxide, thus making it better than traditional sources of biofuels. It can also be harvested every 10 days thus making its oil yield per acre 200 times higher than corn and 40 times higher than sunflowers. The problem is that harvesting and extracting the algae requires large amounts of labor and energy (drying) and the algae may damage surrounding eco-systems. Thus new and better processes along with large scale production are needed to solve these problems. These slides discuss the various approaches (open pond, photo-bioreactor, fermentation), their advantages and disadvantages, their existing and future costs, and other improvements that are driving steadily falling costs. In the short term, algae will continue to be used in niche applications such as cosmetics, food, and fertilizers. In the long run, as the cost reductions continue, algae might become a major source of fuel for transportation and other applications.
Biohydrogen may produced by steam reforming of methane (biogas) produced by anaerobic digestion of organic waste. In the latter process, natural gas and steam react to produce hydrogen and carbon dioxide.
These slides use concepts from my (Jeff Funk) course entitled analyzing hi-tech opportunities to examine the increasing economic feasibility of algae biofuels. Algae can be grown in places where traditional crops cannot be grown and it consumes carbon dioxide, thus making it better than traditional sources of biofuels. It can also be harvested every 10 days thus making its oil yield per acre 200 times higher than corn and 40 times higher than sunflowers. The problem is that harvesting and extracting the algae requires large amounts of labor and energy (drying) and the algae may damage surrounding eco-systems. Thus new and better processes along with large scale production are needed to solve these problems. These slides discuss the various approaches (open pond, photo-bioreactor, fermentation), their advantages and disadvantages, their existing and future costs, and other improvements that are driving steadily falling costs. In the short term, algae will continue to be used in niche applications such as cosmetics, food, and fertilizers. In the long run, as the cost reductions continue, algae might become a major source of fuel for transportation and other applications.
A variety of fuels can be made from biomassi resources including the liquid fuels ethanol, methanol, biodiesel, Fischer-Tropsch diesel, and gaseous fuels such as hydrogen and methane. Biofuels research and development is composed of three main areas: producing the fuels, applications and uses of the fuels, and distribution infrastructure.
Biofuels are primarily used to fuel vehicles, but can also fuel engines or fuel cells for electricity generation. For information about the use of biofuels in vehicles, see the Alternative Fuel Vehicle page under Vehicles. See the Vehicles page for information about the biofuels distribution infrastructure. See the Hydrogen and Fuel Cells page for more information about hydrogen as a fuel.
Microbial biomass conversion processes take advantage of the ability of microorganisms to consume and digest biomass and release hydrogen. Depending on the pathway, this research could result in commercial-scale systems in the mid- to long-term timeframe that could be suitable for distributed, semi-central, or central hydrogen production scales, depending on the feedstock used.
A variety of fuels can be made from biomassi resources including the liquid fuels ethanol, methanol, biodiesel, Fischer-Tropsch diesel, and gaseous fuels such as hydrogen and methane. Biofuels research and development is composed of three main areas: producing the fuels, applications and uses of the fuels, and distribution infrastructure.
Biofuels are primarily used to fuel vehicles, but can also fuel engines or fuel cells for electricity generation. For information about the use of biofuels in vehicles, see the Alternative Fuel Vehicle page under Vehicles. See the Vehicles page for information about the biofuels distribution infrastructure. See the Hydrogen and Fuel Cells page for more information about hydrogen as a fuel.
Microbial biomass conversion processes take advantage of the ability of microorganisms to consume and digest biomass and release hydrogen. Depending on the pathway, this research could result in commercial-scale systems in the mid- to long-term timeframe that could be suitable for distributed, semi-central, or central hydrogen production scales, depending on the feedstock used.
This brief document describes how to convert waste into energy, particularly electricity. It is a new way of waste management. It is eco-friendly and helps fight climate change which has become a global crisis.
Biomethanation of organic waste, Anaerobic degradation,Degradation of organic...salinsasi
Energy has a major economical and political role to play in the modern day society. Energy consumption in the developed countries has more or less stabilized whereas in developing countries like India and China it is increasing at a phenomenal rate. The Government is looking forward to Biomethanation as a secondary source of energy by utilizing industrial, agricultural and municipal solid wastes. A large amount of money is being invested in this direction with various projects under different stages of implementation and many to follow them. Hence the long-term sustainability of the technology needs to be judged. Various potential merits of Biomethanation like reduction in land requirement for disposal, preservation of environmental quality, etc. are the spin off of the process. A study of biomethanation plant in different developed countries and India has been carried out. To understand the technical feasibility in the Indian context, a comparison is made between the characteristics of Indian waste and the ideal wastes characteristics. Further problems of the operational stability, commercial viability of biomethanation in India, developmental plans covering issues in the formulation of national policy, improvements in collection and transportation systems, marketing strategy, and funds allocation has been highlighted .With the growing energy crisis supplemented by environmental concerns, Biomethanation can serve as a potential waste-to-energy generation alternative.
With the ever increasing awareness of green house gases and its adverse impact on the environment, pursue of Biomethanation of Municipal Solid Waste will drastically reduce the emission of CH4 and CO¬2, earning the country precious carbon credits. It will also forge India among developing countries, leading in adoption of technology which suffices the broad guidelines as laid under KAYOTO PROTOCOL.
HYDROGEN GENERATION FROM WASTE WATER BY USING SOLAR ENERGY | J4RV3I11004Journal For Research
Objective of this paper is to produce hydrogen which is an ideal fuel for the next generation because it is abundantly available in nature, energy efficient and clean. Wide varieties of technologies are available to produce hydrogen but only few of them are considered environmental friendly. Solar water splitting via photo catalytic reaction is one of them which have attracted tremendous attention. In this paper we are working on hydrogen production via solar splitting. Photo catalytic water splitting is one of the promising technologies to produce pure and clean hydrogen. Since it is reasonable having low process cost and has a small reactor, it can be made for house hold application and hence has a huge market potential. Generation of hydrogen under visible irradiation is the main area of work. Based on the literature reported here, visible irradiation can be achieved by doping of TiO2 with metal or non-metal. We have used Fe doping to increase the efficiency. The result indicates that Fe doped sieves produce more hydrogen than the normal TiO2 coated sieve and the efficiency can be increased if we increase the number of doped sieves and surface area.
Electricity Generation from Biogas Produced in a Lab-Scale Anaerobic Digester...inventionjournals
The sludge produced during wastewater treatment should be stabilized in order to minimize the damage to the environment. This study includes the evaluation of sludge stabilization and biogas formation by anaerobic digestion in order to generate electricity using stirling motor.The study was carried out with the raw sludge form the thickener of the wastewatertreatment plant. The main aim of the study is to provide sludge stabilization resulting biogas production by reduction of organic matter and to generate electricity. Anaerobic digestion studies were carried out using a laboratory scale anaerobic reactor with a volume of 7L.Under themesophilic condition, the sludge age was maintained at 10 days during the first 20 days of operation, while the reactor was operated for 90 days until the end of the run, with a sludge age of 20 days.The results have changed in the range of 42-52% after the organic matter reduction obtained from the anaerobic digestion. Concentrations of 3735.7300 ppm, 5060.5768 ppm, and 6951.4013 ppm biogas were obtained. Biogas was turned on by mechanical energy with a Stirlingmotor and then turned to direct current and the lamps with 3V 20mA each were run for 60 minutes
MECHANISM OF ANAEROBIC BIODEGRADATION new.pptxmuskanmahajan24
ANAEROBIC DEGRADATION:Anaerobic degradation is defined as the biological process that produce a gas mixture (called biogas) that contains methane (CH4) and carbon dioxide (CO2) as its primary constituents, through the concerted action of a mixed microbial population under conditions of oxygen deficiency.
Biological methane production was first noticed by Volta in 1776, who described the release of methane from a swamp.
Anaerobic digestion is most widely used and one of the oldest methods for sewage sludge stabilization.
It was first used for high-solids municipal wastewater treatment toward the end of the nineteenth century by Louis H. Mouras, who designed and constructed sewage sludge digesters in Vesoul, France.
Complete Aerobic digestion of glucose to carbon-dioxide yields up to 38 mole ATP/mole glucose while Anaerobic fermentation to mixed organic acids yields 2-4 mole ATP/mole glucose.
Microorganisms involved in degradation: Acid - forming bacteria : Clostridium sp , Corynebacterium sp , Lactobacillus sp ,Actinomycetes sp, Staphylococcus sp,Peptococcus anaerobus, Escherichia coli, Pseudomonas,Bifidobacterium, Propionibacterium, Enterobacteriaceae .
Methanogenic bacteria: Methanobacterium formicium,Methanobacterium bryantii, Methanobacterium thermoautotrophicum,Methanosarcina barkeri, Methanobrevibacte ruminantiurn,Methanobrevibacter smithii ,Methanobrevibacter arboriphilus, Methanococcus vannielii , Methanococcus thermolithotrophicus, Methanobacterium cariaci, Methanobacillus omelianskii.
Stages of Anaerobic biodegradation
Hydrolysis, Acidogenesis, Acetogenesis and Methanogenesis
Anaerobic Degradation of Carbohydrates: The anaerobic degradation of cellulose, can be divided into hydrolytic, fermentative, acetogenic and methanogenic phases.
The hydrolysis of carbohydrates proceeds favourably at a slightly acidic pH.
Hemicellulose and pectin are hydrolyzed 10 times faster than lignin-encrusted cellulose.
In the methane reactor, beta-oxidation of fatty acids,especially of propionate or n-butyrate, is the rate limiting step.
Anaerobic degradation of Proteins: Hydrolysis of precipitated or soluble protein is catalyzed by several types of proteases that cleave membrane-permeable amino acids, dipeptides, or oligopeptides.
The hydrolysis of proteins requires a neutral or weakly alkaline pH.
For complete degradadtion of amino acids in an anaerobic system , a syntrophic relationship of amino acids-fermenting anaerobic bacteria with methanogens or sulfate reducers is required.
Anaerobic degradation of Neutral fats and Lipids: Glycerol and saturated and unsaturated fatty acids(palmitic acid,linolic acid,stearic acid etc.) are formed from neutral fats.
The long chain of fatty acids are degraded by acetogenic bacteria by beta-oxidation to acetate and molecular hydrogen.
If acetate and molecular hydrogen accumulate, the anaerobic digestion process is inhibited.
Very low H2 partial pressure is mainatained by hydrogen-utilizing methanogens .
Upflow anaerobic sludge blanket (UASB) technology, normally referred to as UASB reactor, is a form of anaerobic digester that is used in the treatment of wastewater.
The UASB reactor is a methanogenic (methane-producing) digester that evolved from the anaerobic clarigester. A similar but variant technology to UASB is the expanded granular sludge bed (EGSB) digester. A diagramatic comparison of different anaerobic digesters can be found here.
UASB uses an anaerobic process whilst forming a blanket of granular sludge which suspends in the tank. Wastewater flows upwards through the blanket and is processed (degraded) by the anaerobic microorganisms. The upward flow combined with the settling action of gravity suspends the blanket with the aid of flocculants. The blanket begins to reach maturity at around 3 months. Small sludge granules begin to form whose surface area is covered in aggregations of bacteria. In the absence of any support matrix, the flow conditions creates a selective environment in which only those microorganisms, capable of attaching to each other, survive and proliferate. Eventually the aggregates form into dense compact biofilms referred to as "granules".A picture of anaerobic sludge granules can be found here.
Biogas with a high concentration of methane is produced as a by-product, and this may be captured and used as an energy source, to generate electricity for export and to cover its own running power. The technology needs constant monitoring when put into use to ensure that the sludge blanket is maintained, and not washed out (thereby losing the effect). The heat produced as a by-product of electricity generation can be reused to heat the digestion tanks.
The blanketing of the sludge enables a dual solid and hydraulic (liquid) retention time in the digesters. Solids requiring a high degree of digestion can remain in the reactors for periods up to 90 days. Sugars dissolved in the liquid waste stream can be converted into gas quickly in the liquid phase which can exit the system in less than a day.
This presentation will explain the recent technological advancement in Biofuels, processes, technology. Biohydrogen is an emerging technology. OMEGA project Initiated by NASA is the best one.
If you have any questions please write down in the comment box or do contact me at :
cdpm125@gmail.com
Please share this work with others.
Thank You
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
2. Importance of Hydrogen as an Alternative Fuel
• Increased levels of CO2 from fossil
fuels cause an increase in the
Greenhouse Effect
• One of the detrimental effects of the
Greenhouse Effect is Global Warming
• Combustion of Hydrogen produces
water, which is not detrimental to the
environment
3.
4. Hydrogen gas is seen as a future energy carrier by virtue of the fact that it is renewable, does
not evolve the "greenhouse gas" CO2 in combustion, liberates large amounts of energy per
unit weight in combustion, and is easily converted to electricity by fuel cells.
Biological hydrogen production has several advantages over hydrogen production by
photoelectrochemical or thermochemical processes.
Biological hydrogen production by photosynthetic microorganisms for example, requires the
use of a simple solar reactor such as a transparent closed box, with low energy requirements.
Electrochemical hydrogen production via solar battery-based water splitting on the hand,
requires the use of solar batteries with high energy requirements.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18. Biophotolysis of water by microalgae and
cyanobacteria
Microalgae are primitive microscopic plants living in aqueous environments.
Cyanobacteria, formerly known as blue-green algae
Microalgae and Cyanobacteria along with higher plants, are capable of oxygenic
photosynthesis according to the following reaction:
CO2 + H2O 6 [CH2O] + O2.
organic compounds
Photosynthesis consists of two processes:
light energy conversion to biochemical energy by a photochemical reaction,
and CO2 reductin to organic compounds such as sugar phosphates, through the use of
this biochemical energy by Calvin-cycle enzymes.
Under certain conditions, however, instead of reducing CO2,
a few groups of microalgae and Cyanobacteria consume biochemical energy to produce
molecular hydrogen
(Hydrogenase and nitrogenase enzymes are both capable of hydrogen production.
19.
20. Microbial Hydrogen Production
• Types of microbial hydrogen production
• Fermentative
• Photosynthetic (aerobic/anaerobic)
• Most interest in hydrogen production research in US during the Energy
Crisis of the 1970s
• Interest in hydrogen production again in 1990s due to the awareness of
Global Warming, etc.
21. Biophotolysis is a water-splitting process occurring in biological systems.
Molecular O2 and H2 are produced, with light as the energy source.
Biophotolysis proceeds in two distinctive ways—directly and indirectly (Brentner et al., 2010).
Direct biophotolysis has been best studied in the microalgae Chlamydomonas reinhardtii. It relies
on photosystems (both PSI and PSII) and hydrogenase (Fig. 1).
Absorption of light in the form of photons by PSII (680 nm) and/or PSI (700 nm) generates a strong
oxidant that can oxidize water into protons, electrons/reducing equivalents, and O2.
The electrons reduce protons to form H2, according to Equation (1) (Brentner et al., 2010).
22.
23.
24.
25.
26.
27. Theoretically, the energy conversion
efficiency of hydrogenase is higher
than that of nitrogenase. However, it
catalyses a reversible reaction and absorbs
hydrogen in the presence of O2.
Hydrogenase-dependent hydrogen
production therefore requires frequent
anaerobic operations, making it difficult
for large-scale hydrogen production.
28.
29. Anaerobic bacteria metabolize sugars to produce
hydrogen gas and organic acids, but are incapable of
further breaking down the organic acids formed.
the combined use of photosynthetic and anaerobic
bacteria for the conversion of organic acids to
hydrogen. Theoretically, one mole of glucose can be
converted to 12 moles of hydrogen
(In figure)through the use of photosynthetic bacteria
capable of capturing light energy in such a combined
system.
From a practical point of view, organic wastes
frequently contain sugar or sugar polymers. It is not
however easy to obtain organic wastes containing
organic acids as the main components.
The combined use of photosynthetic and anaerobic
bacteria should potentially increase the likelihood of
their application in photobiological hydrogen
production.
30. Anaerobic digestion process includes hydrolysis/acidogenesis and
methanogenesis.
As shown in Figure 1, hydrolysis and acidogenesis produce hydrogen gas and
organic acids, which can be further used to produce methane in methanogenesis.
The hydrogen production step requires 1-2 days hydraulic retention time (HRT)
and methane production step requires longer HRT (12-20 days).
If hydrogen gas is not harvested and further used for methane production, it is
called one-stage fermentation process.
Otherwise it is called two-stage fermentation process
31. • In an anaerobic fermentation process, the hydrogen synthesis pathways are
severely affected by environmental factors, such as pH, temperature and HRT.
• It has widely been accepted in bio-hydrogen research that pH is one of the key
factors affecting the hydrogen production.
• Hydrogen synthesis pathways are sensitive to pH and are subject to end-products
(Craven 1988). Dark hydrogen fermentation reactions can be operated at a
temperature range from mesophilic (25-40o C) to hyperthermophilic (>80o C).
• Up to now, most of dark fermentation experiments are conducted at 35-37o C,
and the possible advantages of operating out of mesophilic range are not
completely clear.
• HRT is also an important parameter for dark fermentation process.
• In continuously stirred tank reactor (CSTR) system, short HRTs were used to
wash out the slow growing methanogens and select for the acid producing
bacteria
• while too short HRT could lead to bad hydrolysis of organic wastes.
32.
33. • Nitrogenase is an enzyme found only in prokaryotes and is concerned with nitrogen fixation
• Nitrogen fixation is a high energy consuming process since it requires several ATP molecules,
and hydrogen is produced as a by-product.
• The nitrogen fixation is carried out by two separate proteins, namely dinitrogenase reductase
(Fe-protein) and dinitrogenase (MoFe-protein).
• The Fe-protein mediates the transfer of electrons from reduced ferredoxin or flavodoxin to
dinitrogenase and brings about conformational changes to the nitrogenase.
• It is an active process, since it requires ATP hydrolysis. Dinitrogenase catalyses both nitrogen
fixation and hydrogenase generation. The nitrogen-fixing cyanobacterium, Anabaena
cylindrica, simultaneously produces hydrogen and oxygen in a nitrogen-free (i.e. argon)
atmosphere.
34.
35.
36.
37. • The nitrogenase enzyme responsible for nitrogen fixation is present in prokaryotes such
as cyanobacteria, and is absent in eukaryotic microalgae.
• The nitrogenase enzyme mediates the reduction of molecular nitrogen into ammonia and
protons into molecular hydrogen with the consumption of reducing power and ATP.
• The efficiency of conversion of light energy to hydrogen by nitrogenase is low (< 1 %)
because of high energy demand.
• The nitrogen-fixing cyanobacteria also possess hydrogenase, which is an uptake
hydrogenase that consumes and reuses hydrogen gas, so that net hydrogen production will
be low.
38. • Nitrogenase is oxygen-sensitive, so the cyanobacteria have evolved mechanisms to
overcome this difficulty.
• The nitrogenase is localized in the heterocysts of filamentous cyanobacteria. The
heterocystous nitrogen-fixing strains like Anabaena are capable of providing an oxygen-
free environment inside the heterocyst so that the oxygen-sensitive nitrogenase can reduce
molecular nitrogen into ammonia and protons into molecular hydrogen.
• The products of oxygenic photosynthesis carried out in vegetative cells are transferred into
heterocysts and decomposed to provide the nitrogenase with reducing power. The
generation of hydrogen can be improved by limiting the supply of molecular nitrogen
39. Advantage:
For large-scale, labour-saving and economical hydrogen
production, nitrogenase is preferred to hydrogenase,
despite its comparatively low theoretical energy
conversion efficiency, because it has the advantage of
catalysing unidirectional production of hydrogen, thus
eliminating the need for a daily anaerobic production-
harvesting cycle.