22 Phycobiliproteins as Food Additives
565
Phycobiliprotein stability measurements are made over a wide range of temperature and pH, measuring changes in the structure and function of the protein,
commonly using spectrophotometric techniques, fluorescence, and measurement of
antioxidant capacity. The thermostable phycobiliproteins have been extracted from
cyanobacteria that live in warmer waters, e.g., the C-phycocyanin of Thermosynechococcus elongatus TA-1, isolated from Taiwan hot springs, is stable between 4
and 60 °C and pH values between 4 and 9, after 4 h of treatment. However, as
with mesophilic phycocyanins above 75 °C, the protein loses its fluorescence due
to denaturation (Leu et al. 2013). Interestingly, the phycoerythrin of the cyanobacterium Leptolyngbya sp. KC 45 also isolated from hot springs, after being exposed
to 60 °C for 30 min maintains 80% of its antioxidant activity determined by
2,2-diphenyl-1-picrylhydrazyl radical (DPPH) (Pumas et al. 2012).
Phycocyanin from Synechococcus lividus PCC 6715 isolated from Yellowstone
National Park hot springs is one of the most stable proteins reported. It showed 90%
stability, after 5 h of incubation at 50 °C and about 70% after two weeks at the same
temperature. Phycocyanin from Synechococcus PCC6715 is slightly more stable than
Thermosynechococcus elongatus TA-1, with 5 h exposure at 50 °C. The phycocyanin
stability of Synechococcus PCC6715 is high at pH 4–8 at 4–50 °C (Liang et al. 2018).
Another reported phycocyanin is that of the thermophilic red alga Cyanidioschyzon merolae isolated from hot springs and geysers has a midpoint denaturation
point at pH 5 at 83 °C with an average lifetime of 40 min (Rahman et al. 2017).
The structural and genomic study of thermostable phycobiliproteins, will allow
to modify the genetic engineering phycobiliproteins to improve the thermostability
in sterilization processes in order to use them safely in different foods.
22.3.2 Phycobiliproteins of Mesophilic Cyanobacteria
Studies in phycobiliproteins in mesophilic cyanobacteria have focused on evaluating
the effect of temperature, pH, light, storage form (dry or in solution) as factors to
preserve the stability with food grade and antioxidant capacity of phycobiliproteins
for use in food or other purposes.
The studies on phycocyanin stability of pH and temperature have been carried out
mainly in the cyanobacterium Spirulina platensis. The phycocyanin of this cyanobacterium is stable in a range of pH 4–8 but at pH 5 the stability of the protein is increased.
At temperatures above 45 °C and pH 7, phycocyanin is denaturated, but when it is at
pH 5–6 its stability is higher, independent of the exposure temperature (Couteau et al.
2004; Patel et al. 2004; Antelo et al. 2008). In agreement with the above, in other
cyanobacteria and red algae has been observed the disappearance of the color of the
phycobiliproteins when exposed to 60–65 °C (Zhao and Brand 1989; Topchishvili
et al. 2002).
In the cyanobacterium Phormidium rubidium A09DM, the phycobiliproteins were
stable in a temperature range of 4–40 °C, but their concentrations decrease to 60–80
°C, as in Spirulina fusiformis (Prasad et al. 2015; Munawaroh et al. 2018).
565
Phycobiliprotein stability measurements are made over a wide range of temperature and pH, measuring changes in the structure and function of the protein,
commonly using spectrophotometric techniques, fluorescence, and measurement of
antioxidant capacity. The thermostable phycobiliproteins have been extracted from
cyanobacteria that live in warmer waters, e.g., the C-phycocyanin of Thermosynechococcus elongatus TA-1, isolated from Taiwan hot springs, is stable between 4
and 60 °C and pH values between 4 and 9, after 4 h of treatment. However, as
with mesophilic phycocyanins above 75 °C, the protein loses its fluorescence due
to denaturation (Leu et al. 2013). Interestingly, the phycoerythrin of the cyanobacterium Leptolyngbya sp. KC 45 also isolated from hot springs, after being exposed
to 60 °C for 30 min maintains 80% of its antioxidant activity determined by
2,2-diphenyl-1-picrylhydrazyl radical (DPPH) (Pumas et al. 2012).
Phycocyanin from Synechococcus lividus PCC 6715 isolated from Yellowstone
National Park hot springs is one of the most stable proteins reported. It showed 90%
stability, after 5 h of incubation at 50 °C and about 70% after two weeks at the same
temperature. Phycocyanin from Synechococcus PCC6715 is slightly more stable than
Thermosynechococcus elongatus TA-1, with 5 h exposure at 50 °C. The phycocyanin
stability of Synechococcus PCC6715 is high at pH 4–8 at 4–50 °C (Liang et al. 2018).
Another reported phycocyanin is that of the thermophilic red alga Cyanidioschyzon merolae isolated from hot springs and geysers has a midpoint denaturation
point at pH 5 at 83 °C with an average lifetime of 40 min (Rahman et al. 2017).
The structural and genomic study of thermostable phycobiliproteins, will allow
to modify the genetic engineering phycobiliproteins to improve the thermostability
in sterilization processes in order to use them safely in different foods.
22.3.2 Phycobiliproteins of Mesophilic Cyanobacteria
Studies in phycobiliproteins in mesophilic cyanobacteria have focused on evaluating
the effect of temperature, pH, light, storage form (dry or in solution) as factors to
preserve the stability with food grade and antioxidant capacity of phycobiliproteins
for use in food or other purposes.
The studies on phycocyanin stability of pH and temperature have been carried out
mainly in the cyanobacterium Spirulina platensis. The phycocyanin of this cyanobacterium is stable in a range of pH 4–8 but at pH 5 the stability of the protein is increased.
At temperatures above 45 °C and pH 7, phycocyanin is denaturated, but when it is at
pH 5–6 its stability is higher, independent of the exposure temperature (Couteau et al.
2004; Patel et al. 2004; Antelo et al. 2008). In agreement with the above, in other
cyanobacteria and red algae has been observed the disappearance of the color of the
phycobiliproteins when exposed to 60–65 °C (Zhao and Brand 1989; Topchishvili
et al. 2002).
In the cyanobacterium Phormidium rubidium A09DM, the phycobiliproteins were
stable in a temperature range of 4–40 °C, but their concentrations decrease to 60–80
°C, as in Spirulina fusiformis (Prasad et al. 2015; Munawaroh et al. 2018).