Abstract
The role of diatoms as a source of bioactive compounds has been recently explored. Diatom cells store a high amount of fatty acids, especially certain polyunsaturated fatty acids (PUFAs). However, many aspects of diatom metabolism and the production of PUFAs remain unclear. This review describes a number of technical strategies, such as modulation of environmental factors (temperature, light, chemical composition of culture medium) and culture methods, to influence the content of PUFAs in diatoms. Genetic engineering, a newly emerging field, also plays an important role in controlling the synthesis of fatty acids in marine microalgae. Several key points in the biosynthetic pathway of PUFAs in diatoms as well as recent progresses are also a critical part and are summarized here.
Highlights
Marine diatoms have been explored recently as sources of secondary metabolites with biological activity
Piepho et al found that the interactive effects of light and phosphorus supply were most pronounced in the diatom Cyclotella meneghiniana, compared with the other two green algae Scenedesmus quadricauda and Chlamydomonas globosa, and a cryptophyte Cryptomonas ovata, and hypothesized that increasing light intensity can lead to higher production of total fatty acids (TFAs), saturated fatty acids (SFAs), and monounsaturated fatty acids (MUFAs), both at low phosphorus concentrations and high phosphorus concentrations in the centric diatom Cyclotella meneghiniana [31]
The results are consistent with the observations in Nitzschia frustulum (Kützing) where a decreasing production of saturated and monounsaturated fatty acids and an increasing production of fatty acids with a high degree of unsaturation were detected at a low temperature treatment (10 °C) [34], which plays a critical role in the maintenance of membrane fluidity [39]
Summary
Marine diatoms have been explored recently as sources of secondary metabolites with biological activity. Diatoms have been attracting increasing interest for their biological characteristics and application value Due to their quantity, industrial scale culture conditions, as well as socio-economic considerations, diatoms are one of the most suitable raw materials for the production of bioactive metabolites. It is generally recognized that the main sources of PUFAs on the market are marine fish because there are no reported definitive examples of land plants accumulating EPA and DHA [16]. Diatoms are metabolically versatile species owing to the fact that they can produce and accumulate a range of bioactive metabolites, such as PUFAs and extracellular polymeric substances [1,26]. Diatoms are single-celled microalgae with fast growth, and it is feasible to manipulate their metabolism to promote the synthesis of PUFAs using biotechnological means, such as genetic manipulation and modified culture conditions [27]. Diatom products do not contain a fishy smell, cholesterol, or pollution by pesticides and heavy metals that most likely appear in fish oil
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