Opportunities and Challenges of Diatom Cell Factory for Human Health

This chapter aims to direct the reader's attention to the great biotechnological potential of diatoms by presenting current knowledge on the content and synthesis of their bioactive compounds. Microalgae— including diatoms—still represent an underexploited resource, even though they present the biological and biochemical characteristics to become one of the main resources for biotechnological applications. This chapter focuses on compound families with renowned benefits for human health. Carotenoids, vitamins, polyphenols, phytosterols, and carbohydrates in diatoms are herein reviewed, reporting information on their composition and intracellular modulation as well as their known biological activities; and fatty acids are also covered in another part the chapter. Also discussed are the promising opportunities diatoms provide in a human health-driven biotechnology context, e.g., as a source of functional ingredients for nutraceuticals, cosmeceuticals or pharmaceuticals. The open challenges to improve their use as biofactories are also discussed. In addition, a section is dedicated to dealing with polar diatoms. Low temperature, lighting (low light, prolonged darkness to long light phase duration), and high UV radiations are abiotic forces inducing physiological and/or biochemical adjustments that could induce the accumulation of potential bioactive compounds. Although those organisms possess great biotechnological potential related to their eco-physiological properties that allow them to successfully grow in extreme environments, there is still little known about their bioactive compounds.