Rhizobium
Rhizobium is a soil habitat bacterium, which
can able to colonize the legume roots and fixes the atmospheric
nitrogen symbiotically. The morphology and physiology of Rhizobium
will vary from free-living condition to the bacteroid of nodules. They
are the most efficient biofertilizer as per the quantity of nitrogen
fixed concerned. They have seven genera and highly specific to form
nodule in legumes, referred as cross inoculation group. Rhizobium
inoculant was first made in USA and commercialized by private
enterprise in 1930s and the strange situation at that time has been
chronicled by Fred (1932).
Initially, due to absence of efficient
bradyrhizobial strains in soil, soybean inoculation at that time
resulted in bumper crops but incessant inoculation during the last four
decades by US farmers has resulted in the build up of a plethora of
inefficient strains in soil whose replacement by efficient strains of
bradyrhizobia has become an insurmountable problem.
Azotobacter
Of the several species of Azotobacter, A. chroococcum
happens to be the dominant inhabitant in arable soils capable of
fixing N2 (2-15 mg N2 fixed /g of carbon source) in culture media. The
bacterium produces abundant slime which helps in soil aggregation. The
numbers of A. chroococcum in Indian soils rarely exceeds 105/g
soil due to lack of organic matter and the presence of antagonistic
microorganisms in soil.
Azospirillum
Azospirillum lipoferum and A. brasilense (Spirillum lipoferum in
earlier literature) are primary inhabitants of soil, the rhizosphere
and intercellular spaces of root cortex of graminaceous plants. They
perform the associative symbiotic relation with the graminaceous
plants. The bacteria of Genus Azospirillum are N2 fixing organisms isolated from the root and above ground parts of a variety of crop plants. They are Gram negative, Vibrio or Spirillum having abundant accumulation of polybetahydroxybutyrate (70 %) in cytoplasm.
Five species of Azospirillum have been described to date A. brasilense, A.lipoferum, A.amazonense, A.halopraeferens and A.irakense.
The organism proliferates under both anaerobic and aerobic conditions
but it is preferentially micro-aerophilic in the presence or absence of
combined nitrogen in the medium. Apart from nitrogen fixation, growth
promoting substance production (IAA), disease resistance and drought
tolerance are some of the additional benefits due to Azospirillum inoculation.
Cyanobacteria
Both free-living as well as symbiotic
cyanobacteria (blue green algae) have been harnessed in rice
cultivation in India. A composite culture of BGA having heterocystous Nostoc, Anabaena, Aulosira etc.
is given as primary inoculum in trays, polythene lined pots and later
mass multiplied in the field for application as soil based flakes to
the rice growing field at the rate of 10 kg/ha. The final product is
not free from extraneous contaminants and not very often monitored for
checking the presence of desiredalgal flora.
Once so much publicized as a biofertilizer
for the rice crop, it has not presently attracted the attention of rice
growers all over India except pockets in the Southern States, notably
Tamil Nadu. The benefits due to algalization could be to the extent of
20-30 kg N/ha under ideal conditions but the labour oriented
methodology for the preparation of BGA biofertilizer is in itself a
limitation. Quality control measures are not usually followed except
perhaps for random checking for the presence of desired species
qualitatively.
Azolla
Azolla is a free-floating water
fern that floats in water and fixes atmospheric nitrogen in association
with nitrogen fixing blue green alga Anabaena azollae. Azolla
fronds consist of sporophyte with a floating rhizome and small
overlapping bi-lobed leaves and roots. Rice growing areas in South East
Asia and other third World countries have recently been evincing
increased interest in the use of the symbiotic N2 fixing water fern Azolla either as an alternate nitrogen sources or as a supplement to commercial nitrogen fertilizers. Azolla is used as biofertilizer for wetland rice and it is known to contribute 40-60 kg N/ha per rice crop.
Phosphate solubilizing microorganisms(PSM)
Several soil bacteria and fungi, notably species of Pseudomonas, Bacillus, Penicillium, Aspergillus etc.
secrete organic acids and lower the pH in their vicinity to bring
about dissolution of bound phosphates in soil. Increased yields of
wheat and potato were demonstrated due to inoculation of peat based
cultures of Bacillus polymyxa and Pseudomonas striata.
Currently, phosphate solubilizers are manufactured by agricultural
universities and some private enterprises and sold to farmers through
governmental agencies. These appear to be no check on either the
quality of the inoculants marketed in India or the establishment of the
desired organisms in the rhizosphere.
AM fungi
The transfer of nutrients mainly phosphorus and also zinc and sulphur from the soil milleu to the cells of the root cortex is mediated by intracellular obligate fungal endosymbionts of the genera Glomus, Gigaspora, Acaulospora, Sclerocysts and Endogone
which possess vesicles for storage of nutrients and arbuscles for
funneling these nutrients into the root system. By far, the commonest
genus appears to be Glomus, which has several species
distributed in soil. Availability for pure cultures of AM (Arbuscular
Mycorrhiza) fungi is an impediment in large scale production despite the
fact that beneficial effects of AM fungal inoculation to plants have
been repeatedly shown under experimental conditions in the laboratory
especially in conjunction with other nitrogen fixers.
Silicate solubilizing bacteria (SSB)
Microorganisms are capable of
degrading silicates and aluminum silicates. During the metabolism of
microbes several organic acids are produced and these have a dual role
in silicate weathering. They supply H+ ions to the medium and promote
hydrolysis and the organic acids like citric, oxalic acid, Keto acids
and hydroxy carbolic acids which from complexes with cations, promote
their removal and retention in the medium in a dissolved state.
The studies conducted with a
Bacillus sp. isolated from the soil of granite crusher yard showed that
the bacterium is capable of dissolving several silicate minerals under in vitro
condition. The examination of anthrpogenic materials like cement, agro
inputs like super phosphate and rock phosphate exhibited silicate
solubilizing bacteria to a varying degree. The bacterial isolates made
from different locations had varying degree of silicate solubilizing
potential. Soil inoculation studies with selected isolate with red
soil, clay soil, sand and hilly soil showed that the organisms
multiplied in all types of soil and released more of silica and the
available silica increased in soil and water.
Rice responded well to application of organic sliceous
residue like rice straw, rice husk and black ash @ 5 t/ha. Combining
SSB with these residues further resulted in increased plant growth and
grain yield. This enhancement is due to increased dissolution of silica
and nutrients from the soil.
Plant Growth Promoting Rhizobacteria (PGPR)
The group of bacteria that
colonize roots or rhizosphere soil and beneficial to crops are referred
to as plant growth promoting rhizobacteria (PGPR).
The PGPR inoculants currently
commercialized that seem to promote growth through at least one
mechanism; suppression of plant disease (termed Bioprotectants),
improved nutrient acquisition (termed Biofertilizers), or phytohormone
production (termed Biostimulants). Species of Pseudomonas and Bacillus
can produce as yet not well characterized phytohormones or growth
regulators that cause crops to have greater amounts of fine roots which
have the effect of increasing the absorptive surface of plant roots
for uptake of water and nutrients. These PGPR are referred to as
Biostimulants and the phytohormones they produce include indole-acetic
acid, cytokinins, gibberellins and inhibitors of ethylene production.
Recent advances in molecular
techniques also are encouraging in that tools are becoming available to
determine the mechanism by which crop performance is improved using
PGPR and track survival and activity of PGPR organisms in soil and
roots. The science of PGPR is at the stage where genetically modified
PGPR can be produced. PGPR with antibiotic, phytohormone and
siderophore production can be made.
Despite of promising results,
biofertilizers has not got widespread application in agriculture mainly
because of the variable response of plant species or genotypes to
inoculation depending on the bacterial strain used. Differential
rhizosphere effect of crops in harbouring a target strain or even the
modulation of the bacterial nitrogen fixing and phosphate solubilizing
capacity by specific root exudates may account for the observed
differences. On the other hand, good competitive ability and high
saprophytic competence are the major factors determining the success of
a bacterial strain as an inoculant.
Studies to know the synergistic
activities and persistence of specific microbial populations in complex
environments, such as the rhizosphere, should be addressed in order to
obtain efficient inoculants. In this regards, research efforts are
made at Agricultural College and Research Institute, Madurai to obtain
appropriate formulations of microbial inoculants incorporating nitrogen
fixing, phosphate- and silicate- solubilizing bacteria and plant
growth promoting rhizobacteria which will help in promoting the use of
such beneficial bacteria in sustainable agriculture.
Liquid Biofertilizers
Biofertilizers are such as Rhizobium, Azospirillum
and Phosphobacteria provide nitrogen and phosphorous nutrients to
crop plants through nitrogen fixation and phosphorous solubilization
processes. These Biofertilizers could be effectively utilized for rice,
pulses, millets, cotton, sugarcane, vegetable and other horticulture
crops. Biofertilizers is one of the prime input in organic farming not
only enhances the crop growth and yield but also improves the soil
health and sustain soil fertility. At present, Biofertilizers are
supplied to the farmers as carrier based inoculants. As an alternative,
liquid formulation technology has been developed in the Department of
Agricultural Microbiology, TNAU, Coimbatore which has more advantages
than the carrier inoculants.
Benefits
The advantages of Liquid Bio-fertilizer over conventional carrier based Bio-fertilizers are listed below:
- Longer shelf life -12-24 months.
- No contamination.
- No loss of properties due to storage upto 45º c.
- Greater potentials to fight with native population.
- High populations can be maintained more than 109 cells/ml upto 12 months to 24 months.
- Easy identification by typical fermented smell.
- Cost saving on carrier material, pulverization, neutralization, sterilization, packing and transport.
- Quality control protocols are easy and quick.
- Better survival on seeds and soil.
- No need of running Bio-fertilizer production units through out the year.
- Very much easy to use by the farmer.
- Dosages is 10 time less than carrier based powder Bio-fertilizers.
- High commercial revenues.
- High export potential.
- Very high enzymatic activity since contamination is nil.
Characteritistics of different liquid Bio-fertilizers
Rhizobium
This belongs to bacterial group
and the classical example is symbiotic nitrogen fixation. The bacteria
infect the legume root and form root nodules within which they reduce
molecular nitrogen to ammonia which is reality utilized by the plant to
produce valuable proteins, vitamins and other nitrogen containing
compounds. The site of symbiosis is within the root nodules. It has
been estimated that 40-250 kg N / ha / year is fixed by different
legume crops by the microbial activities of Rhizobium.
The percentage of nodules occupied, nodules dry weight, plant
dry weight and the grain yield per plant the multistrain inoculant was
highly promising Table-2 shows the N fixation rates.
Quantity of biological N fixed by Liqiud Rhizobium in different crops
Host Group
|
Rhizobium Species
|
Crops
|
N fix kg/ha
|
Pea group
|
Rhizobium leguminosarum
|
Green pea, Lentil
|
62- 132
|
Soybean group
|
R.japonicum
|
Soybean
|
57- 105
|
Lupini Group
|
R. lupine orinthopus
|
Lupinus
|
70- 90
|
Alfafa grp.Group
|
R.mellilotiMedicago Trigonella
|
Melilotus
|
100- 150
|
Beans group
|
R. phaseoli
|
Phaseoli
|
80- 110
|
Clover group
|
R. trifoli
|
Trifolium
|
130
|
Cowpea group
|
R. species
|
Moong, Redgram, Cowpea, Groundnut
|
57- 105
|
Cicer group
|
R. species
|
Bengal gram
|
75- 117
|
Physical features of liquid Rhizobium
- Dull white in colour
- No bad smell
- No foam formation, pH 6.8-7.5
Azospirllium
It belongs to bacteria and is
known to fix the considerable quantity of nitrogen in the range of 20-
40 kg N/ha in the rhizosphere in non- non-leguminous plants such as
cereals, millets, Oilseeds, cotton etc. The efficiency of Azospirillium as
a Bio-Fertilizer has increased because of its ability of inducing
abundant roots in several pants like rice, millets and oilseeds even in
upland conditions. Considerable quantity of nitrogen fertilizer up to
25-30 % can be saved by the use of Azospirillum inoculant. The genus Azospirillum has three species viz., A. lipoferum, A. brasilense and A. amazonense. These species have been commercially exploited for the use as nitrogen supplying Bio-Fertilizers.
One of the characteristics of Azospirillum is its ability to reduce nitrate and denitrify. Both A. lipoferum,and A. brasilense may
comprise of strains which can actively or weakly denitrify or reduce
nitrate to nitrite and therefore, for inoculation preparation, it is
necessary to select strains which do not possess these characteristics. Azospirllium lipoferum present in the roots of some of tropical forage grasses uch as Digitaria, Panicum, Brachiaria, Maize, Sorghum, Wheat and Rye.
Physical features of liquid Azospirillum
-
The colour of the liquid may be blue or dull white.
-
Bad odours confirms improper liquid formulation and may be concluded as mere broth.
-
Production of yellow gummy colour materials comfirms the quality product.
-
Acidic pH always confirms that there is no Azospirillum bacteria in the liquid.
N2 fixing capacity of Azospirillum in the roots of several plants and the amount of N2 fixed by them.
Plant |
Mg N2 fixed /g of substrate |
Oryza sativa (Paddy) |
28
|
Sorghum bicolour (Sorghum) |
20
|
Zea mays (Maize) |
20
|
Panicum sp. |
24
|
Cynodon dactylon |
36
|
Setaria sp |
12
|
Amaranthus spinosa |
16
|
Production of growth hormones
Azospirillum cultures synthesize
considerable amount of biologically active substances like vitamins,
nicotinic acid, indole acetic acids giberllins. All these
hormones/chemicals helps the plants in better germination, early
emergence, better root development.
Role of Liquid Azospirillum under field conditions
-
Stimulates growth and imparts green colour which is a characteristic of a healthy plant.
-
Aids utilization of potash, phosphorous and other nutrients.
-
Encourage plumpness and succulence of fruits and increase protein percentage.
Sign of non functioning of Azospirillum in the field
-
No growth promotion activity
-
Yellowish green colour of leaves, which indicates no fixation of Nitrogen
Azotobacter
It is the important and well known
free living nitrogen fixing aerobic bacterium. It is used as a
Bio-Fertilizer for all non leguminous plants especially rice, cotton,
vegetables etc. Azotobacter cells are not present on the
rhizosplane but are abundant in the rhizosphere region. The lack of
organic matter in the soil is a limiting factor for the proliferation of
Azotobaceter in the soil.
Field experiments were conducted in 1992,
1993 and 1994 during the pre-kharif wet seasons to find out the
influence on rice grain yield by the combined use of N- fixing organisms
and inorganic nitrogen fertilizer which recorded increase in was
yield.
Physical features of liquid Azotobacter
The pigmentation that is produced
by Azotobacter in aged culture is melanin which is due to oxidation of
tyrosine by tyrosinase an enzyme which has copper. The colour can be
noted in liquid forms. Some of the pigmentation are described below-
-
A. chroococcum: Produces brown-black pigmentation in liquid inoculum.
-
A. beijerinchii: Produces yellow- light brown pigementation in liquid inoculum
-
A. vinelandii: Produces green fluorescent pigmentation in liquid inoculum.
-
A. paspali: Produces green fluorescent pigmentation in liquid inoculum.
-
A. macrocytogenes: Produces, pink pigmentation in liquid inoculum.
-
A. insignis: Produces less, gum less, grayish-blue pigmentation in liquid inoculum.
-
A. agilies: Produces green-fluorescent pigmentation in liquid inoculum.
Role of liquid Azotobacter in tissue culture
The study was conducted by Dr. Senthil et al
(2004) on sugarcane variety CO 86032 in Tissue culture Laboratories of
Rajashree Sugars and Chemicals Ltd, Varadaraj nagar, Theni, Tamilnadu.
The liquid bioinoculants were provided by Dr. Krishnan Chandra,
Regional Director, RCOF, Bangalore to evaluate their growth promoting
effects on sugarcane micropropagation. He recorded Biometric
observations like Plant height, leaf length, width, root length, no of
roots. Chemical parameters –Protein, Carbohydrates, N, P,K total
biomass and concluded as follows:
-
The performance of Azotobacter liquid inoculant was c
-
omparatively better than all the treatments in 10 % MS medium followed Azospirillum.
-
The performance of Azotobacter
liquid inoculant was comparatively better than all the treatments
followed by Azosopirillum for the growth of the polybag sugarcane
seedlings.
Role of liquid Azotobacter as a Bio-control agent
Azotobacter have been found to produce some antifungal substance which inhibits the growth of some soil fungi like Aspergillus, Fusarium, Curvularia, Alternaria, Helminthosporium, Fusarium etc.
Acetobaceter
This is a sacharophillic bacteria
and associate with sugarcane, sweet potato and sweet sorghum plants and
fixes 30 kgs/ N/ ha year. Mainly this bacterium is commercialized for
sugarcane crop. It is known to increase yield by 10-20 t/ acre and
sugar content by about 10-15 percent.
Effect of liquid Acetobacter diazotrophicus on sugarcane
In South India use of Azospirillum
and Phospho-bacterium on the cash crop sugarcane is a regular practice
for the past few years with a saving of nearly 20 % of chemical
nitrogen and phosphate applications. Now, it has been reported that a
bacteria Acetobacter diazotrophicus which is present in the
sugarcane stem, leaves, soils have a capacity to fix up to 300 kgs of
nitrogen. This bacteria first reported in brazil where the farmers
cultivate sugarcane in very poor sub-soil fertilized with Phosphate,
Potassium and micro elements alone, could produce yield for three
consecutive harvests, without any nitrogen fertilizer. They have
recorded yield 182- 244 tones per ha. This leads to the assumption that
active nitrogen fixing bacteria has associated within the plant.
Do’s and Don’t for Entrepreneurs, Dealers and farmers
Do
|
Don’t
|
Keep Bio-fertilizers bottles away from direct heat and sunlight. Store it in cool and dry place. |
Don’t store Bio-fertilizers bottles under heat and sunlight |
Sell only Bio-fertilizers
bottles which contain batch number, the name of the crop on which it
has to be used, the date of manufacture and expiry period. |
Don’t sell Bio-fertilizers bottles after their expiry period is over. |
If the expiry period is over, then discard it as it is not effective. |
Don’t prick holes into the bottles or puncture them to pour the content |
Keep Bio-fertilizers bottles away from fertilizer or pesticide containers and they should not be mixed directly. |
Do not mix the Bio-fertilizers with fungicides, insecticides, herbicides, herbicides and chemical fertilizers. |
Liquid Bio-fertlizer application methodology
There are three ways of using Liquid Bio-fertilizers
- Seed treatment
- Root dipping
- Soil application
Seed Treatment
Seed Treatment is a most
common method adopted for all types of inoculants. The seed treatment
is effective and economic. For small quantity of seeds (up to 5 kgs
quantity) the coating can done in a plastic bag. For this purpose, a
plastic bag having size (21” x 10”) or big size can be used. The bag
should be filled with 2 kg or more of seeds. The bag should be closed
in such a way to trap the airs as much as possible. The bag should be
squeezed for 2 minutes or more until all the seed are uniformly wetted.
Then bag is opened, inflated again and shaked gently. Stop shaking
after each seeds gets a uniform layer of culture coating. The bag is
opened and the seed is dried under the shade for 20-30 minutes. For
large amount of seeds coating can be done in a bucket and inoculant can
be mixed directly with hand. Seed Treatment with Rhizobium, Azotobacter, Azospirillum, along with PSM can be done.
The seed treatment can be done
with any of two or more bacteria. There is no side (antagonistic)
effect. The important things that has to be kept in mind are that the
seeds must be coated first with Rhizobium, Azotobacter or Azospirillum.
When each seed get a layer of above bacteria then PSM inoculant has to
be coated as outer layer. This method will provide maximum number of
each bacteria required for better results. Treatments of seed with any
two bacteria will not provide maximum number of bacteria on individual
seed.
Root dipping
For application of Azospirillum/ /PSM on paddy transplating/ vegetable crops this method is used. The required quantity of Azospirillum/
/PSM has to be mixed with 5-10 litres of water at one corner of the
field and the roots of seedlings has to be dipped for a minimum of
half-an-hour before transplantation.
Soil application
Use 200ml of PSM per acre. Mix PSM
with 400 to 600 kgs of Cow dung FYM along with ½ bag of rock phosphate
if available. The mixture of PSM, cow dung and rock phosphate have to
be kept under any tree or under shade for over night and maintain 50%
moisture. Use the mixture as soil application in rows or during
leveling of soil.
Dosage of liquid Bio-fertilizers in different crops
Recommended Liquid Bio-fertilizers
and its application method, quantity to be used for different crops
are as follows:
Crop |
Recommended Bio-fertilizer |
Application method |
Quantity to be used |
Field crops
Pulses
Chickpea, pea, Groundnut, soybean, beans, Lentil,
lucern, Berseem, Green gram, Black gram, Cowpea and pigeon pea
|
Rhizobium
|
Seed treatment
|
200ml/acre
|
Cereals
Wheat, oat, barley
|
Azotobacter/Azospirillum
|
Seed treatment
|
200ml/acre
|
Rice
|
Azospirillum
|
Seed treatment
|
200ml/acre
|
Oil seeds
Mustard, seasum, Linseeds, Sunflower, castor
|
Azotobacter
|
Seed treatment
|
200ml/acre
|
Millets
Pearl millets, Finger millets, kodo millet
|
Azotobacter
|
Seed treatment
|
200ml/acre
|
Maize and Sorghum
|
Azospirillum
|
Seed treatment
|
200ml/acre
|
Forage crops and Grasses
Bermuda grass, Sudan grass, Napier Grass , ParaGrass, StarGrass etc.
|
Azotobacter
|
Seed treatment
|
200ml/acre
|
Other Misc. Plantation Crops
Tobacco
|
Azotobacter
|
Seedling treatment
|
500ml/acre
|
Tea, Coffee
|
Azotobacter
|
Soil treatment
|
400ml/acre
|
Rubber, Coconuts
|
Azotobacter
|
Soil treatment
|
2-3 ml/plant
|
Agro-ForestRY/Fruit Plants
All fruit/agro-forestry (herb,shrubs, annuals and
perennial) plants for fuel wood fodder,
fruits,gum,spice,leaves,flowers,nuts and seeds puppose
|
Azotobacter
|
Soil treatment
|
2-3 ml/plant at nursery
|
Leguminous plants/ trees
|
Rhizobium
|
Soil treatment
|
1-2 ml/plant
|
Note:
Doses recommended when count of inoculum is 1 x 108 cells/ml
then doses will be ten times more besides above said Nitrogen fixers,
Phosphate solubilizers and potash mobilizers at the rate of 200 ml/
acre could be applied for all crops.
Equipments required for Biofertilizer production
In biofertilizer production industry,
equipments are the major infrastructure, which involves 70 percent of
capital investment. Any compromise on the usage of the following
mentioned equipments may finally decline in the quality of
biofertilizer.After studying the principle behind the usage of all
instruments, some of the instruments can be replaced with a culture
room fitted with a U.V.Lamp. Autoclaves, Hot Air Oven, Incubators and
sealing machines are indigenously made with proper technical
specifications. The correct use of equipments will give uninterrupted
introduction with quality inoculum.
Essential equipments
Autoclave
It is an apparatus in which materials are
sterilized by air free saturated steam (under pressure) at a
temperature above 100OC. If the steam pressure inside the autoclave is
increased to 15 psi, the temperature will rise to 121°C. this is
sufficient to destroy all vegetative cells. Normally all growth medium
are sterilized in the autoclave.
Laminar air flow chamber
Laminar air flow chamber provides a uniform
flow of filtered air. This continuous flow of air will prevent settling
of particles in the work area.Air borne contamination is avoided in
this chamber. Culture transfers and inoculation can be done here.
BOD incubators
Incubators providing controlled conditions
(light, temperature, humidity, etc.) required for the growth and
development of microorganisms. Multiplication of starter culture can be
done in this instrument.
Rotary shaker
It is used for agitating culture
flasks by circular motion under variable speed control. Shaking
provides aeration for growth of cultures. Shakers holding upto 20-50
flasks are generally used. The capacity of the shaker may be increased
if it is a double- decker type.
Hot air oven
Hot air oven is meant for
sterilizing all glassware materials. Dry heat is used in this apparatus
to sterilize the materials. Normally 180OC is used for two hours for
sterilizing glasswares.
pH meter
An instrument for measuring pH of
the solution using a 0-14 scale in which seven represents neutral
points, less than seven is acidity (excess of H‘ over OH-) and more
than seven is alkality (excess of OH- over H‘ ) useful in adjusting
the pH of the growth medium.
Refrigerator
This equipment is used preserving
all mother cultures used for biofertilizer production. The mother
culture is periodically sub-cultured and stored in the refrigerator for
long- term usage.
Fermentor
A fermentor is the equipment, which provides
the proper environment for the growth of a desired organism. It is
generally a large vessel in which, the organism may be kept at the
required temperature, pH , dissolved oxygen concentration and substrate
concentration. Different models of fermentors are available depending
upon the necessity. A simple version model contains steam generator,
sterilization process devices and agitator. A sophisticated fermentor
contains pH regulator, oxygen level regulator, anti-foam device,
temperature controller, etc.