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APPLIED MICROBIOLOGY

Takrif Biofertilizers

Preparations containing LIVE or LATENT CELLS of EFFICIENT strains of N2 FIXING, PHOSPHATE

SOLUBILIZING or CELLULOLITIC microorganisms used for applications to SEED, SOIL or COMPOSTING AREAS, with the OBJECTIVE of INCREASING THE NUMBERS of such

microorganisms and ACCELERATE certain microbial PROCESSES to augment the extent of the AVAILABILITY of nutrients in a form which can be easily assimilated by plant

(Subba Rao,NS “Biofertilizers in Agriculture” Oxford & IBH Publishing Company)

TAKRIF (DEFINITION):

Pupuk

Hayati vs Pupuk

Organik

Pupuk dengan bahan aktif Mikroba Terpilih

Pupuk yang berasal dari sisa-sisa tumbuhan & atau hewan dalam berbagai tingkat dekomposisi

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Nitrogen Cycle

• The 2 major processes of N2 transformation are:• Nitrification:

NH4+ → NO3

- : NH4

+ →NO2-

NO2- → NO3

-

• By bacteria e.g. Nitrobacter, Bacillus, Paracoccus, Pseudomonas.

• Denitrification:– NO3

- → N2 • By bacteria e.g. Azotobacter, Clostridium and

Rhizobium.

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Nitrogen Fixation

• N2 is the most stable form of nitrogen and high energy is required to break the N-N triple bond.

• Therefore only microorganisms can fix nitrogen• N2 + 8H+ +8e- →2NH3 + H2

• N2 gas is the greatest reserve of nitrogen.• The productivity of many environs is limited by

the short supply of nitrogenous compounds.• Nitrogen fixation is important to agriculture and

legumes such as soybean can fix atmospheric nitrogen.

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Dentrification

• Denitrification is the reduction of nitrates to N2 or NO2.

• This process is detrimental because it removes nitrogen the environment.

• This is of particular importance to agriculture where nitrate fertilizers are used.

• If anoxic condition develop e.g. water logged soil. The nitrate is remove from the soil by dentrification.

• What do you unerstand by the term “anoxic conditions”?

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Ammonification

• The decomposition of organic nitrogen compounds such as amino acids and nucleotides is called ammonification.

• In the soil much of this NH3 is converted to amino acids by plants.

• Some NH3 is lost by evaporation especially in dense animal populations.

• Globally this constitutes 15% of N2 released to the atmosphere.

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Nitrification

• Nitrification is the oxidation of NH3 to NO3- by nitrifying

bacteria.• The nitrates produced is readily assimilated by plants.• Nitrate is soluble and is quickly leached from the soil.• NH4

+ is +vely charged and will adhere to –vely charged soil (clay) particles.

• NH4+ is extensively used in nitrogenous fertilizers.

• Denitrification consumes N2 while nitrification produces it.

N2 NH33 H2 +

PROSES HABER-BOSCHDALAM INDUSTRI PUPUK N

NH4+ NO2

- NO3-

berbentuk kation tertahan oleh

partikel tanah yang bermuatan negatif relatif stabil dalam tanah

berbentuk anion mobil, tidak tertahan tanah

mudah terlindi, runoff, dan teruapkan dalam bentuk N2O, NO dan N2 melalui

proses denitrifikasi pencemar udara, air tanah

dan perairan

Nitrosomonas Nitrosococcus Nitrosospira Nitrosovibrio Nitrosolobus

Nitrobacter

Methemoglobinemia (blue-baby syndrome)

pada KonsumenNO3

-

NH3

NH3Asam amino

MoNitra

t Reduktase

20 ATP20 ADP

5 ATP

5 ADP

Leaching, Menurunkan kejenuhan basa & memasamkan tanah,

Pencemaran NO3-, Eutrofikasi,

Nitrosamin, Denitrifikasi

Pada tanah2 kahat Mo

NO2-

Terjerap mineral lempung tipe 2 : 1 (Vermikulit, Illit, Mica butir halus & Smektit)

NH4+ lepas

lambat

GS-GOGAT Pathway

NO

N2OGDH Pathway

> 0.5 mg kg-1 tanah< 0.5 mg kg -1 tanah

NH4+

NO3-

Suatu usaha pertanian dapat berkelanjutan apabila menerapkan 2 prasyarat dasar :

1) Pengurangan penggunaan sumberdaya tak terbaharui, sekaligus dengan peningkatan penggunaan sumberdaya terbaharui,

2) Perlindungan lingkungan.

Tidak sekedar untuk meningkatkan produksi tanaman, namun juga bertujuan untuk memelihara agar lingkungan tetap

sehat, baik pada skala lokal, regional, maupun global (mengurangi emisi gas rumah kaca, mempertahankan daur

hidrologi serta keragaman hayati).

1. Konsentrasi N2O di atm. urutan 3 setelah CO2, namun potensi penyerapan per molekulnya thd radiasi gelombang panjang 200 kali >> dibanding CO2

2. Secara katalitik penyebab kerusakan ozon stratosfer

N2ONO

NO3-NH2OH

(hidroksilamin)NH4

+ (HNO)

NO2NHOH(asam hiponitrit)

NO NO

NITRIFIKASI & DENITRIFIKASI menyumbang 50% dari total emisi N2O global & 8–32% total emisi NO (Skiba et al., 1993).

NO2-

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Nitrogen Fixation by Legumes

• The association of nitrogen fixing bacteria with legumes is one of the most important bacteria plant interaction.

• Nitrogen fixing legumes include, soybean, bean, pea, clover and alfalfa are plants with beans in pods.

• Nitrogen fixing bacteria in plants include:RhizobiumBradyrhizobiumMesorhizobiumAzorhizobium

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Nitrogen Fixation

• The symbiotic relationship between plant and nitrogen fixing bacteria results in the formation of a root nodule.

• In the nodule N2 is converted by the enzyme nitrogenase to ammonia.

• The ammonia is used in the synthesis of amino acids and other cellular components.

• Under normal conditions neither Rhizobium nor the plant can fix nitrogen.

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Root Nodules

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Nitrogen Fixation

• Rhizobium can only fix N2 under microaerophilific (reduced O2) conditions.• This is because O2 is needed by

Rhizobium but O2 also inhibits nitrogenase.

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Leghemoglobin

• In the nodule O2 level is reduced by leghemoglobin.

• Leghemoglobin is synthesized only after interaction of the plant and Rhizobium.

• 90% of legumes will fix nitrogen. • However each nitrogen fixing bacteria will

only associate with certain legumes.

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Leghemoglobin

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Steps in Nodule Formation

1. Recognition of the correct partner by both plant and bacteria.

2. Attachment of the bacteria to the plant root.3. Invasion of the root hair by bacteria through the

formation of an infection thread.4. Growth to the main root via the infection thread.5. Formation of bacteroids (deformed bacteria cells) and

development of nitrogen fixing state.6. Continued division of plant and bacteria cell and

formation of mature root nodule.

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Steps in Formation of Root Nodule

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Steps in Formation of Root Nodule

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Nitrogen Fixation

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Bioremediation

• Microorganisms are the Earth’s greatest chemists.

• They can be used to: ▲Extract valuable metals from low grade ore

(microbial leaching).▲Clean up the environment (bioremediation).• Bioremediation is the use of microorganisms to

clean up pollution created by human activity e.g. petroleum and pesticides.

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Bioremediation of Petroleum• Petroleum is a rich hydrocarbon (HC) source and many

organisms including bacteria, mold yeast, cyanobacteria and blue green algae is capable of aerobically oxidize it.

• This type of microbial activity is important in the cleanup of oil and other pollutants.

• In a large oil spill the volatile HC fractions will evaporate.• Hydrocarbon oxidizing microorganisms develop quickly

on the oil film and attach to the aliphatic and aromatic components.

• The will oxidize these HC in the oil to CO2.

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Hydrocarbon Oxidizing bacteria

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Bioremediation of Xenobiotics

• It has been shown that HC oxidizing bacteria can increase in # to 103-106 shortly after an oil spill.

• Xenobiotics are chemically synthesized compounds that are not naturally occurring.

• They include pesticides, polychlorinated biphenyls (PCB, used in electric generation) dyes and many chlorinated solvents.

• Many xenobiotics are structurally related to naturally occurring compounds and as thus can be degraded by microorganisms.

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Bioremediation of Pesticides

• Other Xenobiotics are different and therefore degradation in nature is very slow.

• The most common xenobiotics are pesticides.• Over 1000 pesticides are market for chemical pest

control e.g. herbicide, insecticide and fungicide.• Pesticides include variety of chemicals types including

chlorinated compounds, aromatic rings and nitrogen and phosphorus containing compounds.

• Some of these compounds are suitable carbon source and electron donors for some microorganisms.

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Bioremediation of Pesticides

• If the pesticide can be degraded by microorganisms then it will prevent toxic build up in the soil and water table.

• Chlorinated pesticides are recalcitrant and can persist for more than 10 years

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Persistence of Herbicides and Insecticides in Soil

Substance Time for 75-100% disappearance Chlorinated insecticide DDT 4 years Chlordane 5 years Organophosphate insecticide Malathion 12 weeks Parathion 1 week Herbicides 2,4-D 4 weeks 2, 4,5-T 20 weeks Atrazine 40 weeks

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Bioremediation and Plastics

• Another major environmental concern is the disposal of solid waste particularly plastic.

• The plastic industry produce 40 billion kg of plastic each year, 40% of which end up in landfills.

• Plastics are xenobiotics polymers of various types including:╬Polyethylene╬Polypropylene╬Polystyrene

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Bioremediation and Plastics

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• Many of these polymers are recalcitrant and remain in the landfill for decades.

• One solution is the use of biodegradable polymers such as photobiodegradable plastics, starch-linked and microbially synthesized plastics.

• Photobiodegradable plastics are attacked by UV light (from sunlight) generating polymers which are amenable to microbial attack.

Bioremediation and Plastics

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Biodegradable Plastics

• Starch-based plastics incorporate starch as a for a biodegradable polymer.

• Starch digesting bacteria in the soil attack the starch releasing polymer fragments which are degraded by other microorganisms.

• Microbially synthesized plastic e.g. poly-β-hydroxyalkonate (PHA) is synthesized by microbial cells and can be degraded by microorganisms.