Monday, April 14, 2014

MICROBIAL BIOTECHNOLOGY: SCOPE, TECHNIQUES CONTD

ENVIRONMENTAL APPLICATIONS OF MICROORGANISMS:

3) BIOMINING: HEAVY METAL EXTRACTION USING MICROORGANISMS:

  Biomining utilizes naturally occurring prokaryotic communities. Here,microorganisms are used to leach metals, principally copper but also nickel and zinc, from low-grade sulfide- and/or iron-containing ores. The process exploits the energy metabolism of various acidophilic chemolithoautotrophs that utilize inorganic compounds as energy sources and carbon dioxide as the
source of carbon. These organisms use either ferrous iron or sulfide as an
electron donor and oxygen as an electron acceptor with the formation of
ferric iron or sulfuric acid. In the first case, the subsequent reaction of Ferric ions
with insoluble metal sulfides yields soluble metal sulfates; in the second,
metal sulfides are oxidized directly to metal sulfates. The metals are readily recovered from the leachate by electrolytic procedures, and the residual
solution is recycled.
Gold is inert to microbial action. However, bioleaching of sulfidic gold containing ores under acidic conditions opens up the interior of the ore particles to solvent. After bioleaching, the ore is rinsed with water and the gold is solubilized with a cyanide solution.



MICROBIAL DESULFURIZATION OF COAL:
Coal contains substantial amounts of sulfur, both in pyrite (FeS2) and in organic sulfur compounds (predominantly thiophene derivatives). The composition of coal varies considerably depending on the source. For example, Texas lignite coal contains 0.4% pyrite S and 0.8% organic S, whereas
Illinois coal contains 1.2% pyrite S and 3.2% organic S, by weight. When coal is burned, most of this sulfur is converted to SO2. The SO2 combines with moisture in the atmosphere to form sulfurous acid (H2SO3), a major component of acid smog and acid rain.Microbial desulfurization of coal, by converting the pyrite to ferric sulfate and leaching it out of the coal, provides one way of ameliorating this problem. As much as one or two weeks are required to complete the desulfurization, and large areas of land are required for the leach heaps and the storage of coal.

FUNGAL REMOVAL OF PITCH IN PAPER PULP MANUFACTURING:
In the paper manufacturing industry, treatment of wood with certain white
rot fungi to degrade certain wood extractives before pulping substantially
decreases the toxicity of pulp mill effluent toward aquatic organisms. Compounds that are extractable from wood with organic solvents make up
between 1.5% and 5.5% of the dry weight of softwoods (angiosperms) and
hardwoods (gymnosperms). These compounds, called wood extractives,
consist mainly of triglycerides, fatty acids, diterpenoid resin acids, sterols, waxes, and sterol esters. Resin acids are present in most softwoods but are generally absent or are minor components in hardwood
species. During wood pulping and refining of paper pulp, the
wood extractives are released,forming colloidalparticles commonly referred
to aspitchorresin. These colloidal particles form deposits in the pulp and
in the machinery. These deposits can cause mill shutdowns and various
quality defects in the finished paper products. Moreover, the resin constituents in pulp mill effluent show acute toxicity toward fish and aquatic
organisms.
Pretreatment of the wood with fungi to degrade some of the wood extractives before pulping has met with considerable success. Basidiomycete fungi
and Ophiostoma species colonize living and recently dead wood. Many of
the species in this genus are referred to as sap-staining or blue-staining fungi
because they stain colonized wood.To avoid this problem,a commercial fungal product, Cartapip, utilizes an “albino” strain of Ophiostoma piliferum.
When applied to wood chip piles, this fungus has been particularly effective

in degrading triglycerides and fatty acids in both softwoods and hardwoods but only partially effective in the removal of other pitch-forming compounds
(sterols, sterol esters, and waxes) or the biotoxic resin acids. After four weeks
of treatment at a moisture level of 70% on a wet wood weight basis at 27 C,O.
piliferum produced up to a 50% reduction in the pitch content of softwoods,
with less than a 5% loss of woody mass. Moreover, the effluent
biotoxicity was reduced 11- to 14-fold compared with untreated controls.
A number of white rot basidiomycete fungi are able to degrade the
sterol esters and waxes. Several different bacteria, isolated by enrichment
of pulp mill effluent, are able to degrade resin acids. There is now a substantial amount of work that demonstrates that fungi and bacteria, as well 
as enzymes derived from these organisms, are capable of minimizing pitch
deposition during the pulping process and substantially decreasing the toxicity of the effluents.

Cited By Kamal Singh Khadka
Msc Microbiology, TU.
Assistant Professor In Pokhara University, Pokhara Bigyan Thata Prabidhi Campus, PNC, LA, NA.
Pokhara, Nepal.

Some Suggested References:
idosi.org/aeja/2(2)09/6.pdf‎
whitman.myweb.uga.edu/coursedocs/mibo4300/biomining.PDF
www.siemens.com/innovation/apps/pof.../_pof.../biomining.html‎
www.ncbi.nlm.nih.gov › Journal List › Front Microbiol › v.3; 2012‎
https://www.mysciencework.com/.../the-use-thermophilic-organisms-for-...‎
www.ic.ucsc.edu/~saltikov/courses_backup/archive.../Nies_1999.pdf‎
www.saimm.co.za/Conferences/Hydro2009/101-110_M-Bafubiandi.pdf‎




















Wednesday, April 9, 2014

MICROBIAL BIOTECHNOLOGY: SCOPE, TECHNIQUES CONTD

ENVIRONMENTAL APPLICATIONS OF MICROORGANISMS:

2) BIO REMEDIATION: Bioremediation depends on the activities of living organisms to clean up pollutants dispersed in the environment. Physical or chemical treatments, such
as vaporization, extraction, or adsorption, relocate rather than remove pollutants. In contrast, there are many instances in which biodegradation converts organic pollutants to harmless inorganic products, including carbon dioxide, water, and halide ions. Other advantages are that bioremediation
is generally inexpensive and causes little disturbance to the environment. Naturally occurring consortia, frequently dominated by bacteria, have the capacity to degrade a wide spectrum of environmental pollutants.
  Notably, such consortia are responsible for the cleanup of massive oil spills. There is a long list of oil spills with serious environmental impact. Following are three of many examples of this type of widely dispersed pollution. In March 1989, some 41 million liters (>10.5 million gallons) of crude oil
escaped from the tanker Exxon Valdez and contaminated more than 2000 km (∼1250 miles) of rocky intertidal coastline in Alaska. In 1991, during the Gulf War, huge amounts of oil were released into the marine environment, with devastating impact on marine life. In 1997, more than 5000 tons of heavy oil leaked from the Russian tanker Nakhodka, which ran aground and sank in the Sea of Japan. The oil contaminated more than 500 km (∼310 miles) of the coastline. Over time, in all of these cases, the endogenous microbial community largely degraded the oil. In the case of the Exxon Valdez, the activity of the naturally occurring hydrocarbon-degrading bacteria at the spill site
was enhanced by the addition of fertilizer containing organic nitrogen compounds and inorganic phosphorus compounds.
Many thousands of organic and inorganic compounds are used daily
around the world in hundreds of thousands of products. These compounds
are introduced either accidentally or on purpose into the soil and groundwater. The seriousness of the problem posed by the introduction of human made contaminants into the environment is highlighted by the following pronouncement by the Danish government in 2003: The government’s most important goal with regard to chemicals is that by 2020 there should no longer be any products or goods on the market containing chemicals with particularly problematic health or environmental impacts.
   Among such pollutants, highly chlorinated compounds have received particular attention because of their known and potential adverse environmental and health impacts. One class of such compounds includes highly chlorinated aliphatics such as tetrachloroethene, trichloroethene, 1,1,1-trichloroethane, and carbon tetrachloride, which are used as dry cleaning
fluids and degreasing solvents. Another class is represented by highly chlorinated aromatics such as pentachlorophenol (wood preservative), polychlorobiphenyls (insulators, heat exchangers), and dioxins (combustion byproducts). These compounds are either fully or partially degraded by the
combined activities of various endogenous microorganisms under aerobic
or anaerobic conditions. By and large, the natural attenuation of chlorinated
organic compounds at many different sites by the action of endogenous
microbial populations, whether under aerobic or anaerobic conditions, is
slow, is incomplete, and, in some cases, has resulted in the formation of
toxic products up of sites contaminated by radionuclides poses an exceptionally
challenging problem of great importance. A U.S. Department of Energy
(DOE) report summarizes the situation succinctly.
With the end of the Cold War threat in the early ’90s and the subsequent shutdown of all nuclear weapons production reactors in the United
States, DOE has shifted its emphasis to remediation, decommissioning,
and decontamination of the immense volumes of contaminated water and
soils, and the over 7,000 structures spread over 120 sites (7,280 square kilometers) in 36 states and territories. DOE’s environmental legacy includes
1.7 trillion gallons of contaminated ground water in 5,700 distinct plumes,
40 million cubic meters of contaminated soil and debris, and 3 million
cubic meters of waste buried in landfills, trenches, and spill areas.” Source:
U.S. Department of Energy. (2003).Bioremediation of Metals and Radionuclides. What Is It and How It Works, LBNL-42595, 2nd Edition, p. 5, Washington, D.C.: Office of Biological and Environmental Research, Office of Science, U.S. Department of Energy.
Subsurface bioremediation of such sites has attracted much attention. A
key objective is to stabilize the buried wastes in place to prevent leaching and
widespread contamination of groundwater. The most common radioactive
components inthese wastes are uranium(U),strontium(Sr),plutonium(Pu),
cesium (Cs), and technetium (Tc).

CITED BY KAMAL SINGH KHADKA/ SHAILENDRA PARAJULI
Msc Microbiology, TU.
Assistant Professor Of Pokhara University, PBTPC, PNC,LA, NA.
Pokhara, Nepal.

Suggested References:
en.wikipedia.org/wiki/Bioremediation‎
ei.cornell.edu/biodeg/bioremed
water.usgs.gov/wid/html/bioremed.html‎
www.epa.gov/tio/download/.../a_citizens_guide_to_bioremediation.pdf‎
www.clu-in.org/bioremediation/‎
www.omicsonline.org/bioremediation-biodegradation.php‎
www.springer.com/cda/content/.../cda.../9783540211013-c1.pdf?...0...
www.ncbi.nlm.nih.gov/pubmed/12111139‎
www.cee.ucr.edu › Department of Chemical Engineering‎
biotech.about.com › Industry › Biotech / Biomedical › Glossary‎
www.ncbi.nlm.nih.gov/pubmed/11930989‎
























Sunday, March 30, 2014

MICROBIAL BIOTECHNOLOGY: SCOPE, TECHNIQUES CONTD

ENVIRONMENTAL APPLICATIONS OF MICROORGANISMS:

Microorganisms mitigate a multitude of impacts that result from human
use of the natural resources of the planet. First and foremost, the essential
role of microorganisms in the treatment of waste water is critical to the well being of life on Earth. Bio-remediation, bio-mining, and microbial desulfurization of coal are other large-scale processes in which important positive environmental outcomes are achieved by directly exploiting the combined metabolic capabilities of naturally occurring communities of microorganisms. In such applications, the functioning of a particular microbial community can be influenced through the manipulation of conditions (e.g., nutrients, oxygen tension, temperature, agitation).
1) WASTE WATER TREATMENT:
       Living organisms consist of about 70% water. A human being, for instance,
has to consume an average of 1.5 L/day to survive.Freshwater represents only
about 2.5% of the water on the planet  and is now a scarce resource
in many parts of the world. The volume of water being contaminated and
the need to reclaim waste water are increasing with the growth in population and industrial use. Waste water originates from four primary sources: sewage,industrial effluents, agricultural runoff, and storm water and urban runoff. Treatment of waste water is essential to prevent contamination of drinking water and entry of pathogens and contaminants in food chain.
Primary treatment of sewage consists of removal of suspended solids. The secondary treatment of
sewage reduces the biochemical oxygen demand. This is accomplished by lowering the organic compound content of the effluent from the primary treatment through microbial oxidation by an incompletely characterized community of microorganisms in “activated sludge.” Bacteria of Zoogloea species play an important role in the aerobic secondary stage of sewage treatment. These organisms produce abundant extra-cellular polysaccharide and, as a result, form aggregates called flocs. Such aggregates efficiently adsorb organic matter, part of which is then metabolized by the bacteria.
The flocs settle out and are transferred to an anaerobic digester, where other bacteria complete the degradation of the adsorbed organic matter.
The microbial communities in a water treatment plant convert organic carbon to carbon dioxide, water, and sludge; convert some 80%of the ammonia and nitrate to molecular nitrogen; remove some soluble phosphate
through incorporation into the sludge, either as polyphosphate granules within bacterial cells or as struvite (crystalline MgNH4PO4); and remove pathogenic bacteria.
However, serious challenges in waste water treatment have yet to be fully addressed. The level of residual fixed nitrogen compounds and of phosphate in the effluent is still high enough to pose risks of eutrophication in the receiving bodies of water. Residues of many widely used pharmaceuticals present in municipal waste-water are incompletely removed and emerge in the effluent. Some of these compounds are biologically active at nano grams per liter and have demonstrable undesirable environmental effects. The chemical industry uses thousands of synthetic organic compounds in huge amounts,and many of these (or their degradation products) pose a similar concern to the pharmaceutical ones. Finally, waste-water treatment consumes energy but converts much of the ammonia and nitrate to nitrogen gas, and a significant amount of the phosphate remains in the effluent. Alternative processes that would recover the fixed nitrogen compounds and phosphate would offset the energy and economic costs of manufacturing the corresponding amount of chemical fertilizer and lessen the acute environmental problems associated with elevated nutrient levels in aquatic ecosystems.

NOTE: Biological Oxygen Demand
Maintenance of high oxygen concentration in aquatic ecosystems is essential for
the survival of fish and other aquatic organisms. Decomposition of organic matter
may rapidly deplete the oxygen. When organic matter such as untreated sewage
is added to an aquatic ecosystem, it is degraded by bacteria that consume oxygen
in the process. The biological oxygen demand (BOD) is related to the amount of
organic matter in the water. Usually, the oxygen consumption is measured over
a period of five days and is abbreviated BOD5. BOD5 for municipal wastewater
generally ranges from 80 to 250 mg O2 per liter. Appropriate secondary treatment
decreases the BOD5 to less than 20 mg O2 per liter.

Cited By Kamal Singh Khadka/ Shailendra Parajuli
Msc Microbiology, TU.
Assistant Professor In Pokhara University, PBTPC, PNC, LA, NA.
Pokhara, Nepal.

SOME SUGGESTED REFERENCES :
www.highveld.com/microbiology/environmental-microbiology.htm
textbookofbacteriology.net/Impact.html‎
www.lbl.gov/Science-Articles/Archive/microorganisms-phylotypes.html
www.researchgate.net/...microorganisms...environmental/.../9fcfd50abeb.
www.ncbi.nlm.nih.gov/pubmed/20662374‎
www.academia.edu/.../Role_of_Microorganisms_on_Wastewater_Treatm.
bartec-benke.nl/media/.../thebiologicalbasisofwastewatertreatment.pdf‎
kyocp.wordpress.com/.../types-of-bacteria-used-in-wastewater-treatment/
www.microtack.com/html/natural_sewage_treatment.htm‎
www.riparia.org.rs/aqua/activated-sludge.htm‎
mimoza.marmara.edu.tr/~neslihan.semerci/ENVE100/ENVE100Ch5.pdf‎
ic.ucsc.edu/~saltikov/bio119/lecture/25_lecture_wastewater_part.pdf‎
https://www.boundless.com/.../wastewater-treatment.../wastewater-and-se..
binodpandey.files.wordpress.com/2011/02/waste-water.pdf‎
https://www.theseus.fi/bitstream/handle/10024/.../Regmi_Shakil.pdf?...1
www.nepjol.info › Home › Our Nature › Vol 6, No 1 (2008) › Rajbanshi
www.ncbi.nlm.nih.gov › NCBI › Literature › PubMed Central (PMC)‎






























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Sunday, March 23, 2014

MICROBIAL BIOTECHNOLOGY: SCOPE, TECHNIQUES CONTD

SINGLE CELL PROTEIN:
The term single-cell protein, or SCP, describes the protein-rich cell mass derived from microorganisms grown on a large scale for either animal or human consumption. SCP has a high content of protein containing all the essential amino acids. Microorganisms are an excellent source of SCP because of their rapid growth rate, their ability to use very inexpensive raw materials as carbon sources, and the uniquely high efficiency, expressed as grams of protein produced per kilogram of raw material, with which they transform these carbon sources to protein. In spite of these advantages,only one SCP product approved for human consumption has reached the market. This product is “mycoprotein,” the processed cell mass preparation from the filamentous fungus Fusarium venenatum. We  consider here the positive nutritional properties of this product and examine the many concerns that needed to be examined and addressed before this product gained regulatory approvals. The source organism,F. venenatum strain PTA-2684, was cultured
from a soil sample obtained from  Buckingham shire, United Kingdom. Marlow Foods Ltd. chose this strain
of F. venenatum from more than 3000 organisms obtained from around the world. The manufacturing process for mycoprotein is designed to ensure the absence of undesirable constituents of fungal cells from the final product .
F. venenatum is grown with aeration under steady-state conditions maintained by continuous feed of nutrient medium and concomitant removal of the culture. These fermentation conditions were chosen to prevent the production of the highly toxic mycotoxins. Fusarium species produce trichothecene and fusarin mycotoxins when growth is limited by nutrient limitation, a high ratio of carbon to nitrogen nutrients, low oxygen tension, or the lack of a micro-nutrient. To prevent mycotoxin synthesis, the production strain is grown at a high rate without any nutritional limitations. The culture is supplied with a nutritionally balanced, chemically defined fermentation medium, with glucose as the sole carbon source. The medium is provided at a rate that allows the cells to grow at a specific rate of at least 0.17 per hour. To monitor the levels of mycotoxins, the final product is analyzed for these compounds by high-performance liquid chromatography with mass spectrometric detection. The detection limits per kilogram wet weight of product are 2µg for
individual trichothecenes and 5µg for fusarin mycotoxins. With these sensitivity levels, no mycotoxins are detected in the final product.
Rapidly growing bacterial and fungal cells are rich in RNA. RNA in the diet is broken down into purines and pyrimidines. Purines are converted to uric acid and add the serum uric acid derived from the metabolism
of endogenous purines. Elevated uric acid increases the risk of developing out and kidney stones in susceptible individuals. To address this problem, a United Nations Protein Advisory Group recommended in 1972 that SCPs intended for human consumption provide no more than 2 g of RNA per day. The fermentation broth containing the fungal biomass removed from the fermentor is rapidly by injection of steam.
The rapid heating process kills the cells, with concomitant degradation of RNA. The fermentation
broth is subsequently separated from the cell mass by centrifugation, and  the RNA degradation products are discarded with the supernatant. These steps reduce the content of RNA in the cell mass from about 10% in viable cells to about 0.5% to a maximum of 2% in mycoprotein on a dry weight basis. With estimated limits of dietary intake of mycoprotein of 17 to 33 g/person/day on a dry weight basis, the intake of RNA from consumption of mycoprotein would range from 0.35 to 0.7 g/person/day, well below the level recommended by the United Nations Protein Advisory Group. Animal studies have shown that mycoprotein does
not cause chronic toxicity, is not a reproductive toxicant, is not a teratogen, and is not carcinogenic. It does
not interfere with the absorption of calcium, iron, or other essential inorganic nutrients. Marlow Foods Ltd.reported that mycoprotein is much less allergenic in humans than are many commonly consumed foods,
such as those containing shellfish or peanuts. Anecdotal reports hint at higher numbers of adverse reactions.
Mycoprotein has been commercially available in the United Kingdom since 1985, in other countries in
Europe since 1991, and in the United States since 2002. Products marketed in Europe include meat-free burgers and fillets and prepared meals, such as stir-fries, curries, and pasta dishes, in which mycoprotein is the central component. In the United Kingdom and Europe, the acceptance of mycoprotein as a meat substitute in a wide variety of foods has been significant,with a reported 15 million customers. The story of mycoprotein illustrates the long road of regulatory approvals and customer acceptance that a new SCP product must travel.

NOTE:  Mycotoxins are synthesized by Fusarium species as well as by members of other
genera of filamentous fungi, such as Aspergillus and Penicillium. Mycotoxins are  products of fungal secondary metabolism. Thus, they are not essential to the energy producing or biosynthetic metabolism of the fungus, or to fungal reproduction. Rather, under growth-limiting or stress conditions, they appear to give the fungus an advantage over other fungi and bacteria with which it may be competing. Mycotoxins are nearly all cytotoxic. They disrupt cell membranes and interfere with protein, RNA, and DNA synthesis. Their toxicity extends beyond microorganisms to the cells of higher plants and animals, including humans.
Fusarium species produce different classes of mycotoxins, trichothecenes and fusarins. Deoxynivalenol, also known as vomitoxin, is one of about 150 related trichothecene compounds that are formed by a number of species of Fusarium and some other fungi. Deoxynivalenol is nearly always formed before harvest when crops are invaded by certain species of Fusarium closely related to Fusarium venenatum. These Fusarium species are important plant pathogens that cause heat blight in wheat. Deoxynivalenol is heat stable and persists in stored grain.

Cited By Kamal Singh Khadka/ Shailendra Parajuli
Msc Microbiology, TU.
Assistant Professor In PU, PBTPC,PNC, LA, NA.
Pokhara, Nepal.

SUGGESTED REFERENCES:
biomaster2011.blogspot.com/‎
www.researchgate.net/.../49619680_Single_Cell_Protein_Production_an.
www.nature.com/nature/journal/vaop/ncurrent/full/nature12904.html
www.slideshare.net/FIRDOUS88/single-cell-protein‎
www.sandia.gov/biosystems/docs/singlecell.pdf‎
www.ncbi.nlm.nih.gov/pubmed/24402228‎
en.wikipedia.org/wiki/Fusarium_venenatum‎
en.wikipedia.org/wiki/Mycoprotein‎
www.biotopics.co.uk/edexcel/biotechnol/myco.html‎
www.researchgate.net/...Production...Mycoprotein...Fusarium_venenatum

                                            Fig: Fusarium Spp

































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Tuesday, March 18, 2014

MICROBIAL BIOTECHNOLOGY: SCOPE, TECHNIQUES CONTD

FOOD TECHNOLOGY: 

MONENSIN
                Monensin is the most widely used compound fed to cattle to increase feed
efficiency. In feedlot cattle, a dosage of 350 mg/day led to an improvement
in feed efficiency of approximately 6%. In grazing cattle, the average daily
gain increased by 15%. Monensin produces these outcomes by changing the
makeup of the bacterial population in the rumen, thereby influencing the
balance of the end products of ruminal fermentation metabolism. 
Monensin is produced by the bacterium Streptomyces cinnamonensis. It is a member of a large and important class of polyketides, the poly ether ionophores. The compound is toxic to many bacteria, fungi, protozoa, and higher organisms. The pKa of the carboxyl group in monensin is 7.95, so at the acidic pH of the rumen, the uncharged lipophilic molecule accumulates in cell membranes of bacteria sensitive to this ionophore. Monensin forms cyclic complexes with alkali metal cations (Na ion, K ion, Rb ion) with a preference for Na ion, with six oxygen atoms serving as  ligands to the cation. The ratio of Na ion / K ion 
concentrations in the rumen ranges from 2 to 10. The direction of metal ion and proton movement across a cell membrane is directed by the magnitude of the existing ion concentration gradient. Monensin acts as an “antiporter” that releases a proton at the inner face of the cytoplasmic membrane as it picks up K ion 
 At the outer face of the cytoplasmic membrane, it releases the K ion and picks up either H ion or Na ion. The cell responds to these ion fluxes by utilizing its Na/K and H ion ATPase's to maintain ion balance and intracellular pH. Depending on the extent of exhaustion of ATP, and of the resulting membrane depolarization, the cells cease to grow and reproduce, and may die. 

In the anaerobic environment  of the rumen, ruminal microorganisms generate the energy and nutrients for their growth by fermenting carbohydrates (primarily cellulose) and proteins. The major resulting products, volatile fatty acids (acetic, propionic, and butyric) and microbial protein, serve as the sources of
energy and nutrients for the cow.The fatty acids pass through the rumen wall into the bloodstream. The cow
derives most of its energy from the oxidation of these compounds. Degradation of the microbial cells in the gastrointestinal tract provides amino acids. However, other bacterial fermentation end products, particularly methane and ammonia that are released to the environment, represent loss to the cow of a sizeable fraction of the potential energy and protein sources from the feed. The major end products of the fermentative metabolism of the Gram positive bacteria in the rumen are acetate, butyrate, formate, lactate, hydrogen, and ammonia. The methanogenic bacteria in the rumen are not able to use complex organic compounds. They obtain energy by utilizing formate, acetate, carbon dioxide, and  hydrogen to generate methane. 
The effects of monensin on ruminal fermentation are as follows. Much less methane is produced. The ratio of propionate to acetate is higher. Less ammonia is produced, and the amount of protein N available to the cow is greater. How does monensin modulate the fermentative metabolism in the rumen? 
  The recommended daily dosage of monensin is 350 mg, the mass of the
monensin–Na+ The recommended daily dosage of monensin is 350 mg, the mass of the monensin–Na+ complex is 693 , and the rumen volume of cattle is approximately 70 L. Thus, the initial ruminal  concentration of unbound monensin–Na+ is 7µM. At such a low concentration, monensin–Na+
rapidly partitions into the membranes of the most sensitive bacteria.
However, studies with radio labeled monensin show that binding also takes place to feed particles,
protozoa, and ionophore-resistant bacteria. The potential binding sites are
far from saturated at this monensin concentration. Gram-positive ruminal bacteria are more sensitive to monensin than are Gram-negative ones. In general, bacteria with outer membranes and/or associated extra cellular polysaccharide are more resistant, presumably because of the hindrance of access of monensin to the cytoplasmic membrane. Under these conditions, monensin does not inhibit methanogenic bacteria but does inhibit the Gram-positive H2-producing bacteria that supply the methanogens with H2 and that also produce acetate, butyrate, and formate. The result is a decrease in methane production. The fermentative pathways of ruminal Gram-negative bacteria lead to propionate and succinate. These organisms are not inhibited by monensin. The overall result is an increase in organisms are not inhibited by monensin. The overall result is an increase in the propionate-to-acetate ratio, in essence an increase in the energy source
for the cow.  The ruminal obligate amino acid–fermenting bacteria are monensin sensitive. The inhibition of 
these bacteria produces the large observed decrease in ammonia production.  The consequence is that more protein N is available to the cow.
In summary, monensin modulates ruminal fermentative metabolism by
selective inhibition of the metabolic activities of particular groups of bacteria. However, studies with
radio labeled monensin show that binding also takes place to feed particles,
protozoa, and ionophore-resistant bacteria. The potential binding sites are
far from saturated at this monensin concentration. Gram-positive ruminal bacteria are more sensitive to monensin than are Gram-negative ones.

In general, bacteria with outer membranes and/or associated extra cellular polysaccharide are more resistant, presumably because of the hindrance of access of monensin to the cytoplasmic membrane.
Under these conditions, monensin does not inhibit methanogenic bacteria but does inhibit the Gram-positive H2-producing bacteria that supply the methanogens with H2 and that also produce acetate, butyrate, and formate. The result is a decrease in methane production. The fermentative pathways of ruminal Gram-negative bacteria lead to propionate and succinate . These  organisms are not inhibited by monensin. The overall result is an increase in the propionate-to-acetate ratio, in essence an increase in the energy source
for the cow. The ruminal obligate amino acid–fermenting bacteria are monensin sensitive. The inhibition of these bacteria produces the large observed decrease in ammonia production. The consequence is that more protein N is available to the cow.
In summary, monensin modulates ruminal fermentative metabolism by selective inhibition of the metabolic activities of particular groups of bacteria.


Cited By Kamal Singh Khadka/ Shailendra Parajuli
Msc Microbiology, TU.
Assistant Professor In Pokhara University, Pokhara Bigyan Thata Prabidhi Campus, PNC, LA, NA.
Pokhara, Nepal.

Some Suggested References:
 www.biolegend.com/monensin-solution-1000x-1500.html‎
en.wikipedia.org/wiki/Monensin‎
www.journalofanimalscience.org/content/43/3/670.full.pdf‎
www.fda.gov/AnimalVeterinary/Products/.../ucm129991.htm
www.elanco.us/products-services/beef/rumensin-p.aspx‎
www.ncbi.nlm.nih.gov › Journal List › Can Vet J › v.46(10); Oct 2005
www.ncbi.nlm.nih.gov/pubmed/2160275‎
www.ncbi.nlm.nih.gov/pubmed/6378867‎
aac.asm.org/content/55/2/745‎
journalofanimalscience.org/content/58/6/1518.full.pdf+html‎















































Saturday, March 15, 2014

MICROBIAL BIOTECHNOLOGY: SCOPE, TECHNIQUES CONTD

FOOD TECHNOLOGY:
PREPARATION OF FERMENTED FOODS:
The use of microorganisms to produce fermented foods has a very long history. Microbial fermentation is essential to production of wine,beer,bologna, buttermilk, cheeses, kefir, olives, salami, sauerkraut, and many more . The metabolic end products produced by the microorganisms flavor fermented foods. For example, mold-ripened cheeses owe their distinctive flavors to the mixture of aldehydes, ketones, and short-chain fatty acids produced by the fungi. Lactic acid bacteria are widely used to produce fermented foods. These organisms are also of particular importance in the food fermentation industry because they produce peptides and proteins(bacteriocins) that inhibit the growth of undesirable organisms that cause food spoilage and the multiplication of food borne pathogens. The latter include Clostridium botulinum(the cause of botulism) and  Listeria monocytogene(which produces meningoencephalitis, meningitis, perinatal septicemia, and other disorders in humans).
NISIN: 
Nisin, an antimicrobial peptide produced by strains of Lactococcus lactis, is widely used as a preservative at low concentrations (up to 250 ppm in the finished product) primarily in heat-processed and low pH foods. Nisin inhibits the growth of a wide range of Gram-positive bacteria, including Listeria, Clostridium, Bacillus, and enterococci, but is not effective against Gram-negative bacteria, yeasts, and molds. The antibacterial activity of nisin is the combined outcome of its high affinity interaction with lipid II at the outer leaflet of the bacterial cytoplasmic membrane and permeabilization of the membrane via pore formation. 
  Nisin is designated as a Generally Regarded as Safe (GRAS) food preservative in the United States and in many other countries around the world. It is used in many food products, including pasteurized cheese spreads with fruits, vegetables, or meats; liquid egg products; dressings and sauces; fresh
and recombined milk; some beers; canned foods; and frozen dessert. 

LACTOBACILLUS SAKEI: A PROMISING BIO PRESERVATIVE

L. sakei, a psychrophilic lactic acid bacterium, was first isolated from sake, a Japanese rice beer that is produced partly by lactic acid fermentation. Subsequently,L. sakei strains were found to dominate the spontaneous fermentation of meat in the manufacture of salami and other dry fermented sausages. Such strains are also major components of the microbial flora of processed food products stored at cold temperature. L. sakei starter cultures have come to be widely used in the manufacture of fermented meats, and this organism has been shown to prevent the growth of spoilage organisms and pathogens.L. sakei is also a transient inhabitant of the human gut. A number of other lactic acid bacteria are either transient or permanent members of the human gastrointestinal flora, including Lactobacillus acidophilus. In that setting, these organisms – called probiotic species – stimulate the immune response and suppress the growth of potentially pathogenic bacteria. Recently, the genome of L. sakei23K, isolated from
a French sausage, was completely sequenced and was 43% identical to Lacidophilus. There is much interest in using safe bacteria as bio preservatives, and for the various reasons outlined above,L. sakei is an excellent candidate. The availability of the complete genome of L. sakei23K allows one to formulate testable hypotheses as to the attributes of this organism that enable it to flourish on fresh meat and to survive stressful conditions it encounters during meat fermentation and storage. Such challenges include high levels
of oxidative stress, high salt, and low temperatures. The L. sakei genome codes for four proteins predicted to be involved in cell–cell interaction and in binding to collagen exposed on the surface of
meat. Such proteins are absent from other lactobacilli. Two other gene clusters are predicted to function in the production of surface polysaccharides that may contribute to the attachment of the bacterium to the meat surface.  These protein and polysaccharide surface components might mediate the
aggregation of L. sakei and formation of a biofilm on the meat surface that would exclude other microorganisms. Meat undergoes auto proteolysis on aging with release of amino acids.L. sakei is auxotrophic for all amino acids (except glutamic and aspartic), and  thus the meat surface is an excellent ecological niche. Meat storage frequently requires refrigeration and salts (up to 9% NaCl).
L. sakei is well adapted to both low temperature and the osmotic stresses
encountered at high salt concentrations. It has a larger number of putative
cold stress proteins than other lactobacilli. It also has uptake systems for the
efficient accumulation of osmo- and cryoprotective solutes such as betaine
and carnitine.L. sakei is also well equipped with enzymes that detoxify reactive oxygen species such as superoxide or organic hydroperoxides generated during meat processing. Finally,L. sakei requires and takes up both heme and iron from the meat. The competition for iron may represent yet another important factor in the ability of L. sakei to exclude other organisms from the meat surface.

Cited By Kamal Singh Khadka/ Shailendra Parajuli 
Msc Microbiology, TU. 
Assistant Professor In Pokhara University, Pokhara Bigyan Thata Prabidhi Campus, PNC, LA , NA.
Pokhara, Nepal.

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