Production of agarose, production of hydrocolloids ,marine biotechnology ,marine biology, marine natural products, applications of algae, uses of red algae, applications of agar, uses of agar,

1. Production of
agarose
Presented by
S.Kaayathri Devi
19PO03
II M.Sc., Biotechnology

2. What is agar and agarose?
 Agar is a polysaccharides derived from
algae especially red algae such as
Gelidium,Gracillaria.
 They are hydrocolloids
 The basic structure of agar is a regularly
alternating sequence of 3-1-galactose and
4-linked 3,6-anhydro-L -galactose

3.  Agar a mixture of two polysaccharides:
agarose and agaropectin
 Agarose is a linear polymer, made up of
repeating units of agarobiose,a
disaccharide made up of D-galactose and
3,6-anhydro-L-galactopyranose

4. Gelidium
Gracilaria

5. The steps required to obtain
agar from seaweed are -
 1. Cleaning of seaweed
 2. Chemical pre-treatment
 3. Extraction of seaweed
 4. Filtration and gelation of extract
 5.Freezing-Thawing method
 6.Syneresis method

6. 1.CLEANING OF SEAWEED
 Agar is insoluble in cold water and the
seaweed may safely be washed with water
to remove soluble impurities, such as salt,
as well as to assist in the separation of
foreign matter, such as other weeds, sand,
stone and pieces of coral.

7. 2.CHEMICAL PRETREATMENT
 The seaweed is given a strong alkaline treatment before extraction. This
causes hydrolysis of sulfate groups and transforms important quantities of L-
galactose 6-sulfate into 3,6- anhydro-L-galactose, thereby significantly increasing
the gel strength of the agar obtained.
 0.25-0.5M sodium hydroxide solution at 80°C for 3-5 hours.
Acid pre-treatment
 The purpose of the acid is to soften the weed and prepare it for extraction.
 Treatment is accomplished by immersing the weed for 10-15 minutes
containing the dilute acid, usually hydrochloric.

8. 3.EXTRACTION
 Agar is extracted from seaweed using hot
water.
 Adjustment of the pH is sometimes
beneficial.
 The use of certain additives, such as
phosphates, is claimed to improve yield or
colour.
 The seaweed is usually added to boiling
water in the extraction vessel, which is
heated by live steam introduced through

9. Contd…
pipes at the bottom of the vessel.
 After addition of the seaweed, boiling is
continued for between 1and half to 3
hours.
 Test the samples of extract and weed at
intervals with fingers; good gel formation
and the right ‘feel’ when the weed is
pressed between the fingers indicate that
extraction is complete.

10.  Gelidium is more resistant and extraction
under pressure (105-110°C for 2-4 hours) is
faster and gives higher yields.
 Gracilaria is usually treated with water at
95-100°C for 2-4 hours.
 Extract concentrations ranges from 0.8%
to 1.5%.

11. 4.FILTRATION
 The extract is thick and will gel if allowed to
cool, so it must be kept hot during the
filtration processes.
 Filter presses with fine filter cloth are the
most useful ones.
 The filtrate is cooled to form a gel, which is
broken into pieces.
 The gel may be treated with bleach to
reduce any colour, washed to remove the
bleach, and allowed to soak in water so
that the salts can be removed by osmosis.

12. 5.Freezing-Thawing method
 The gel is slowly frozen so that large ice
crystals form. The structure of the gel is
broken down by the freezing so that when
the material is thawed most of the water
drains away, leaving a concentrated gel
that now contains about 10-12 percent agar
 Temperatures ranging from -10°C to -20°C

13.  Removal of low molecular weight
polysaccharides, as well as proteins from
the algae including phycoerytrins that
produce the red colour of the
Rhodophyceae family.

14. 6.Syneresis method
 Syneresis is used to describe the process
where pressure is used to exude liquid
fromthe gel.
 The water that soaks the colloidal net of
the gel is eliminated by applying, by
suitable means, a force that will favour
such loss.
 The agar gel was wrapped in canvas
cloths and placed in a series of steel
boxes fitted between the fixed and

15. Contd…
movable heads of a vertical hydraulic press.
 This treatment was followed by hydraulic
pressing, once the product was consistent
enough to withstand extrusion.
Freezing-thawing method is relatively
expensive compared to syneresis
 Agar by syneresis as the dry extract weight
after pressing is as high as 20% compared
to 11% in freezing

16.  Agar by freezing has double the water
content where the impurities stay while
syneresis eliminates more soluble
impurities.
 This is reflected in the lower ash content
found in syneresis agar.

18. Applications of agar in food
industry
 Agar is used as a thickening agent in low
calorie marmalades, jams, processed
meat products, bakery fillings, icings,
prepared soups, ice-creams, etc.
 As a gelation agent in doughnuts, low
calorie marmalades, jams, jelly candy, fruit
yogurts, acidified creams, cheese,
puddings, custards, flans, fruit desserts,
whipped fruit pulp, etc.

20. APPLICATIONS IN DENTAL
 Dentagars are technical agar powders to
be used in dental impression applications.
 Dentagars are offered with different gel
strengths and different meshes.

21. APPLICATIONS IN PHARMA
INDUSTRY
 Pharmaceutical Agar is used in the
pharmaceutical industry for many
applications such as suspending agent for
Barium Sulphate Radiology, intestine
regulation, surgical lubricants and in
preparations of emulsions, suspensions,
capsules, etc.

22. APPLICATIONS IN
LABORATORIES
 In the field of plant tissue culture .for the
propagation of orchids and other
ornamental plants, vegetables ,fruits and
other agricultural products.
 As a culture media for all pathogenic and
nonpathogenic bacteria and fungi in
Microbiology.

24. References
https://www.slideshare.net/Palash12/extracti
on-of-agarose-from-seaweeds
https://www.slideshare.net/nishankwaghmar
e1/agar-122374094
https://www.indiaagar.com/application-of-
agar
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