270
12 Collagen
proteins, fish skin and other residues attached to the scales. The solid and liquid
are then separated. This can then be followed by either rinsing or addition of acid
until neutral. The scales are then washed in tap water followed by distilled water.
The scales are then dried until bone dry and they can be stored in this form until
needed. Alternatively, they can be frozen until needed depending on the facilities
available. The cleaned washed scales are then extracted in distilled water in the ratio
1–10 wet weight of scales to volume of water in a closed vessel where the pressure
is around 80 kPa. The pressure prevents evaporation of water and also allows the
water molecules to penetrate into the scales. The duration of extraction could range
between 3 and 20 h depending on the desired yield. Optimal yield is obtained at
80 °C after 8 h. Further extracts were obtained up until 20 h, however, most of the
collagens were removed by 8 h (Olatunji and Denloye 2017).
The liquid extract which contains hydrolyzed collagen polypeptides is then separated from the solid residue which is mainly made up of calcium carbonate and
chitin, using a filter cloth or sieve. Further separation with a centrifuge at 2500 rpm
for 15 min is then done to separate smaller particles. The liquid filtrate is then evaporated on a hot plate or in an oven until a viscous liquid is formed. This is then solvent
cast and allowed to dry forming into sheets which can then be milled in granules or
processed into other desired forms such as pellets. The advantage of this method is
the minimal requirement for additional chemicals. This puts most of the cost of the
heat required to rupture the collagen structure to release the polypeptides.
12.5.3 Extraction of Collagen from Jellyfish
Collagen obtained from jellyfish is of particular interest due to recent findings that
polypeptides from these collagens have some antioxidant, hemostatic and antihypertensive bioactivities (Zhuang et al. 2009, 2012; Cheng et al. 2017). Extraction
of collagen can be carried out using the enzyme pepsin, and this has been used for
extraction of collagen from aquatic sources such as jellyfish and starfish (Felician
et al. 2019; Tan et al. 2013) used pepsin enzyme. 203 g of jellyfish filaments which
had been washed with ultrapurified water was then homogenized in a 50% w/v acetic
acid for 10 min. The extraction is then carried out using 1% pepsin under constant
stirring at 4 °C. The extraction was carried out for a duration of 72 h. Centrifugation
at 8000 rpm for 15 min was then used to separate the extracted collagen from the
other components. The collagen was then precipitated out by adding sodium chloride
at 2 and 0.05 mol/L tris to get a pH of 7. Further centrifugation was then carried out
at 10,000 rpm for 20 min to separate the precipitate. This is then dissolved in 50%
acetic acid. Dialysis against acetic acid is at 0.1 mol/L and ultrapure water for 2 h and
2 days, respectively. Advantage of this method for extraction of collagen is that it is
done at low temperature of 4 °C such that the collagen can be obtained in its whole
form rather than degraded into collagen peptides. Such method is desirable when the
whole collagen is needed, the main cost therefore goes into use of the enzyme and
maintaining the conditions required for the enzyme to function. To obtain collagen
12 Collagen
proteins, fish skin and other residues attached to the scales. The solid and liquid
are then separated. This can then be followed by either rinsing or addition of acid
until neutral. The scales are then washed in tap water followed by distilled water.
The scales are then dried until bone dry and they can be stored in this form until
needed. Alternatively, they can be frozen until needed depending on the facilities
available. The cleaned washed scales are then extracted in distilled water in the ratio
1–10 wet weight of scales to volume of water in a closed vessel where the pressure
is around 80 kPa. The pressure prevents evaporation of water and also allows the
water molecules to penetrate into the scales. The duration of extraction could range
between 3 and 20 h depending on the desired yield. Optimal yield is obtained at
80 °C after 8 h. Further extracts were obtained up until 20 h, however, most of the
collagens were removed by 8 h (Olatunji and Denloye 2017).
The liquid extract which contains hydrolyzed collagen polypeptides is then separated from the solid residue which is mainly made up of calcium carbonate and
chitin, using a filter cloth or sieve. Further separation with a centrifuge at 2500 rpm
for 15 min is then done to separate smaller particles. The liquid filtrate is then evaporated on a hot plate or in an oven until a viscous liquid is formed. This is then solvent
cast and allowed to dry forming into sheets which can then be milled in granules or
processed into other desired forms such as pellets. The advantage of this method is
the minimal requirement for additional chemicals. This puts most of the cost of the
heat required to rupture the collagen structure to release the polypeptides.
12.5.3 Extraction of Collagen from Jellyfish
Collagen obtained from jellyfish is of particular interest due to recent findings that
polypeptides from these collagens have some antioxidant, hemostatic and antihypertensive bioactivities (Zhuang et al. 2009, 2012; Cheng et al. 2017). Extraction
of collagen can be carried out using the enzyme pepsin, and this has been used for
extraction of collagen from aquatic sources such as jellyfish and starfish (Felician
et al. 2019; Tan et al. 2013) used pepsin enzyme. 203 g of jellyfish filaments which
had been washed with ultrapurified water was then homogenized in a 50% w/v acetic
acid for 10 min. The extraction is then carried out using 1% pepsin under constant
stirring at 4 °C. The extraction was carried out for a duration of 72 h. Centrifugation
at 8000 rpm for 15 min was then used to separate the extracted collagen from the
other components. The collagen was then precipitated out by adding sodium chloride
at 2 and 0.05 mol/L tris to get a pH of 7. Further centrifugation was then carried out
at 10,000 rpm for 20 min to separate the precipitate. This is then dissolved in 50%
acetic acid. Dialysis against acetic acid is at 0.1 mol/L and ultrapure water for 2 h and
2 days, respectively. Advantage of this method for extraction of collagen is that it is
done at low temperature of 4 °C such that the collagen can be obtained in its whole
form rather than degraded into collagen peptides. Such method is desirable when the
whole collagen is needed, the main cost therefore goes into use of the enzyme and
maintaining the conditions required for the enzyme to function. To obtain collagen