Biomedical Engineering Reference
In-Depth Information
Utilization of microalgae for human health and as a foodstuff by indigenous populations has a
long history. Indeed, edible blue-green algae, including Nostoc, Arthrospira ( Spirulina ) and
Aphanizomenon species, have been used for food for thousands of years (Jensen et al ., 2001 ).
The first commercial large scale microalgal cultivation started in the early 1960s in
Japan with the culture of Chlorella by Nihon Chlorella. As a dry product, Chlorella is
composed of about 45% protein, 20% fat, 20% carbohydrate, 5% fiber, and 10% minerals
and vitamins (Belasco, 1997). In the 1960s health foods became available in the form of
tablets, granules and drinks as well as food additives in Japan (Yamaguchi, 1997). However,
Chlorella has proved difficult to produce on a large scale and digestibility problems have
also arisen in nutritional studies due to the tough cell wall of these species. An interesting
side-line to this story is the use of so-called 'Japanese Chlorella ' as a health food and for
aquaculture. While superficially similar to genuine Chlorella , detailed studies and
biochemical analyses showed that this was actually a eustigmatophyte of the genus
Nannochloropsis , which is notable for having a high content of the polyunsaturated fatty
acid 20:5n-3 (Volkman et al ., 1993 ).
In the early 1970s a harvesting and culturing facility for Arthrospira was established in
Mexico by Sosa Texcoco SA (Spolaore et al ., 2006 ). Arthrospira is used in human nutrition
because of its high protein content and its excellent nutritive value. A number of possible
health-promoting effects have also been claimed, including the alleviation of hyperlipidemia,
suppression of hypertension, protection against renal failure, growth promotion of intestinal
Lactobacillus , and suppression of elevated serum glucose level (an overview has been given
by Spolaore et al ., 2006 ).
Arthrospira ( Spirulina ) production for nutraceuticals is a commercial success story.
Companies such as Cyanotech Corporation and Earthrise in the United States have established
a market for nutraceuticals from Spirulina , which is sold as a 'superfood', and when grown
using naturally occurring deep-sea nutrients these products can be accredited with organic
status. However, most Arthrospira ( Spirulina ) production occurs in China and India.
The cyanobacterium Aphanizomenon flos-aquae contains approximately 60% protein by
dry weight and is known to contain an array of digestible nutrients, including essential fatty
acids such as linoleic acid (18:2n-6) and linolenic acid (18:3n-3). A. flos-aquae has been
harvested commercially in Oregon, USA, from naturally occurring algal blooms as a source
of nutraceuticals (Carmichael et al ., 2000 ).
Microalgae are extensively utilized in aquaculture as live feeds for all growth stages of
bivalve molluscs (e.g. oysters, scallops, clams and mussels), for the larval and early juvenile
stages of abalone, crustaceans and some fish species, and as booster feeds for zooplankton
such as rotifers, copepods and Artemia used as live feeds. The microalgae must be of an
appropriate size for ingestion, e.g. from 1 to 15 μm for filter feeders; 10 to 100 μm for grazers
(Webb and Chu, 1983; Jeffrey and co-workers, 1992) and can be readily digested (Brown et
al ., 1997; Volkman and Brown, 2006). The algal species must have rapid growth rates, be
amenable to mass culture, and also be robust and stable in culture to any fluctuations in
temperature, light and nutrients, as often occurs in aquaculture hatcheries. As well, the
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