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13 Starch
Food security is increasingly becoming a global concern. Starch forms an important part of the human diet and making up over half of the global calorie intake. It is
a major source of carbohydrate and energy food. Although approximately 65 million
tonnes of starch are produced annually in the world and constantly increasing at an
annual rate of 2–3% (Sullivan-Trainor 2013; McWilliams 2017), much more starch
would be required if it is to serve as a sustainable source of biofuel as well as a
component of food and other products used by humans.
Starch is one of the major polymers being explored to solve one of the biggest
global crises of single-use plastic pollution through the development of starch-based
bioplastic packaging. It is therefore pertinent to seek alternative, preferably more
abundant source of starch which do not interfere with the human consumption of
starch and starch-based products but rather augments it where possible. Conventional starch sources are maize, rice, wheat, potato, tapioca and cassava. From these,
starches for biofuel, bioplastic, food and other starch-based products must be sourced.
In addition to the existing and potential application of aquatic-sourced starch to
create products, the process of cultivating and processing of aquatic-sourced starch
should also be considered in order to understand the overall impact of aquatic-sourced
starch as a biopolymer resource. This chapter therefore discusses the sources, availability, production process, chemistry, potential applications and the impact on the
environment and global economy of starch sourced from aquatic ecosystems.
13.2 Occurrence in Nature
Starch, a major energy storage carbohydrate, occurs naturally in plants. It is present
in the leaves, seeds, fruits, stems, roots and tubers. It is also present in red, brown
and green macroalgae and microalgae (Prabhu et al. 2019). These photosynthetic
organisms absorb light energy from the sun and store it in chemical form as starch.
Aquatics plants like the water hyacinth, duckweed and Azolla are examples of aquatic
sources of starch. These starch-producing organisms can be found in both marine
and freshwater (Zhang et al. 2018) in varying amounts. The starch content of any
given organism depends on factors such as species and abiotic factors of the aquatic
ecosystem, and it is growing within.
Microalgae contain a considerably large amount of starch. On average, they contain around 37% starch by weight. Strains such as Chlamydomonas, Chlorella,
Spirulina, Dunaliella, Scenedesmus have the most abundant starch content which
could be as much as 50% carbohydrates most of which is starch (Rehman and Anal
2018). At optimized conditions, the cultivation of the green marine microalgae strain
Tetraselmis subcordiformis with starch content of up to 62.1% dry weight has been
achieved (Yao et al. 2012). These findings suggest that not only is starch present in
microalgae but also that the rate of starch accumulation in the microalgae biomass
can be controlled and thus optimized through the limitation of nutrients.
The rate of accumulation of starch and biomass within the aquatic organism is
affected by the environmental conditions as well as the nutrients available for growth.
13 Starch
Food security is increasingly becoming a global concern. Starch forms an important part of the human diet and making up over half of the global calorie intake. It is
a major source of carbohydrate and energy food. Although approximately 65 million
tonnes of starch are produced annually in the world and constantly increasing at an
annual rate of 2–3% (Sullivan-Trainor 2013; McWilliams 2017), much more starch
would be required if it is to serve as a sustainable source of biofuel as well as a
component of food and other products used by humans.
Starch is one of the major polymers being explored to solve one of the biggest
global crises of single-use plastic pollution through the development of starch-based
bioplastic packaging. It is therefore pertinent to seek alternative, preferably more
abundant source of starch which do not interfere with the human consumption of
starch and starch-based products but rather augments it where possible. Conventional starch sources are maize, rice, wheat, potato, tapioca and cassava. From these,
starches for biofuel, bioplastic, food and other starch-based products must be sourced.
In addition to the existing and potential application of aquatic-sourced starch to
create products, the process of cultivating and processing of aquatic-sourced starch
should also be considered in order to understand the overall impact of aquatic-sourced
starch as a biopolymer resource. This chapter therefore discusses the sources, availability, production process, chemistry, potential applications and the impact on the
environment and global economy of starch sourced from aquatic ecosystems.
13.2 Occurrence in Nature
Starch, a major energy storage carbohydrate, occurs naturally in plants. It is present
in the leaves, seeds, fruits, stems, roots and tubers. It is also present in red, brown
and green macroalgae and microalgae (Prabhu et al. 2019). These photosynthetic
organisms absorb light energy from the sun and store it in chemical form as starch.
Aquatics plants like the water hyacinth, duckweed and Azolla are examples of aquatic
sources of starch. These starch-producing organisms can be found in both marine
and freshwater (Zhang et al. 2018) in varying amounts. The starch content of any
given organism depends on factors such as species and abiotic factors of the aquatic
ecosystem, and it is growing within.
Microalgae contain a considerably large amount of starch. On average, they contain around 37% starch by weight. Strains such as Chlamydomonas, Chlorella,
Spirulina, Dunaliella, Scenedesmus have the most abundant starch content which
could be as much as 50% carbohydrates most of which is starch (Rehman and Anal
2018). At optimized conditions, the cultivation of the green marine microalgae strain
Tetraselmis subcordiformis with starch content of up to 62.1% dry weight has been
achieved (Yao et al. 2012). These findings suggest that not only is starch present in
microalgae but also that the rate of starch accumulation in the microalgae biomass
can be controlled and thus optimized through the limitation of nutrients.
The rate of accumulation of starch and biomass within the aquatic organism is
affected by the environmental conditions as well as the nutrients available for growth.