# Microalgal Proteins and Bioactives for Food, Feed, and Other Applications
## 1 Introduction
### Microalgae for Pharmaceutical Applications  
Red biotechnology defines the use of biotechnology in the medical and pharmaceutical industries and health preservation [103]. There is demand for further screening of different microalgae species and strains and the development of new potential pharmaceutical agents derived from microalgae biomass [104]. Antioxidants hold potential for development as health-promoting ingredients and for maintenance of food quality and safety. Well-known antioxidants include carotenoids and peptides derived from microalgae. Carotenoids prevent cell damage by quenching cellular reactive oxygen species (ROS) such as superoxide anion, hydrogen peroxide or hydroxyl radicals, which result in increased oxidative stress and subsequent lipid peroxidation and protein oxidation. Oxidative stress results from an imbalance of homeostasis between oxidant and antioxidant species in the cell with excessive production of ROS and free radicals [105]. Carotenoids can protect human cells from inflammatory and metabolic disorders, early ageing, cardiovascular diseases, arthritis and cancer by quenching ROS and free radicals [86]. Several studies indicate that an increase in the intake of astaxanthin, for example, helps to prevent the development of type 2 diabetes mellitus (T2 DM), reduces systolic blood pressure and protects the consumer from diseases associated with metabolic syndromes as well as atherosclerosis, neurodegenerative and cardiovascular diseases [106]. Moreover, a sufficient intake of \(\beta\)-carotene can decrease the damaging effect of free radicals associated with different types of cancer and plays a role in restoring the activity of antioxidant hepatic enzymes, which protect hepatic cells from xenobiotics, for example [86; 107]. Microalgae sterols are lipids that make up the cell membrane and influence its fluidity and permeability. They can lower blood cholesterol significantly and are reported to reduce total cholesterol by 10% and LDL cholesterol by up to 15%. Species known to produce phytosterols in high amounts are _Isochrysis galbana_ and _Pavlova lutheri_. Moreover, significant anti-cancer and anti-inflammatory effects of microalgae sterols were previously described. In a study by [PERSON] and colleagues, lipid extracts from _Nannochloropsis_ sp. reduced plasma and liver cholesterol in rats significantly. In contrast, a lipid extract derived from _Nannochloropsis galatana_ was found to reduce blood glucose and LDL cholesterol, while the concentration of blood insulin and HDL cholesterol increased [75]. As mentioned earlier, PUFAs are an important group of bioactive molecules with significant, positive effects on human health. Eicosapentaenoic acid (EPA) helps with the regulation of blood pressure, regulation of the immune system response, protection against cancer and atherosclerosis and treatment of anxiety and depression. Docosahexaenoic acid (DHA) showed significant anticancer activity previously and has positive impacts on the functionality of the nervous system and human fetus development. Gamma linoleic acid is successfully used for the treatment of autoimmune diseases, allergies and obesity [8]. Another interesting group of microalgae bioactive molecules with the potential for use in pharmaceutical applications includes therapeutic proteins. The advantages of