*3.2. Uses for Health and Well-Being Promotion*

In the human being, oxidation reactions driven by reactive oxygen species can lead to protein damage and DNA decay or mutation; these may in turn lead to several syndromes, *viz*. cardiovascular diseases, some kinds of cancer and degenerative diseases, and ageing at large [17,27]. As potent biological antioxidants, carotenoids are able to absorb the excitation energy of singlet oxygen radicals into their complex ringed chain—thus promoting energy dissipation, while protecting tissues from chemical damage. They can also delay propagation of such chain reactions as those initiated by degradation of polyunsaturated fatty acids—which are known to dramatically contribute to the decay of lipid membranes, thus seriously hampering cell integrity [21]. 

One illustrative example is the decline of cognitive ability accompanying Alzheimer's disease, which is apparently caused by persistent oxidative stress in the brain [28]. Using transgenic mice fed with extracts from *Chlorella* sp. containing Άcarotene and lutein, Nakashima *et al.* [29] claimed significant prevention of cognitive impairment. Wu *et al*. [30] used also *Chlorella* extracts containing 2–4 mg/gDW of lutein, and reported reduction in the incidence of cancer, as well as prevention of macular degeneration [31]. Likewise, carotenoids extracted specifically from *Chlorella ellipsoidea* and *Chlorella vulgaris* inhibited colon cancer development [23]. Furthermore, astaxanthin obtained from *Haematococcus pluvialis* decreased expression of cyclin D1, but increased that of p53 and some cyclin kinase inhibitors of colon cancer cell lines [32]. 

Carotenoids have also the ability to stimulate the immune-system, thus being potentially involved in more than 60 life-threatening diseases—including various form of cancer, coronary heart diseases, premature ageing and arthritis [33]; this is specifically the case of canthaxanthin and astaxanthin, and other nonprovitamin A carotenoids from *Chlorella* but to a lesser degree [23]. A few epidemiological studies encompassing Ά-carotene from *Dunalliela* sp.—which contains readily bioavailable 9-*cis* and all-*trans* stereoisomers (*ca*. 40% and 50%, respectively), have indeed provided evidence of a lower incidence of several types of cancer and degenerative diseases [34]. Finally, carotenoids exhibited hyperlipidemic and hypercholesterolemic effects [19]. 

## **4. Industrial Production**

The worldwide demand for carotenoids was *ca*. 640 M€ in 2004, but it has been rising ever since at an average yearly rate of 2.2% [9]; Ά-carotene has specifically risen from *ca*. 175 M€ in 2004 to 

*ca*. 183 M€ in 2009 [35]. A growing fraction has been accounted for by carotenoids from biotechnological sources; and Ά-carotene, as well as such xanthophylls as astaxanthin, cantaxanthin and lutein have consequently been in higher and higher demand [9]. The most famous source microalgae are *Chlorella*, *Chlamydomonas*, *Dunaliella*, *Muriellopsis* and *Haematococcus* spp.—all of which belong to the Chlorophyceae family [2]. They tend to accumulate carotenoids as an intrinsic part of their biomass, thus offering economical alternatives to chemical synthesis [36]. 

Among all natural sources studied to date, *Dunaliella* possesses the highest content of 9-*cis* Ά-carotene [20,34]—reaching levels up to 100 g/kgDW, [19,37,38]; Άcarotene-rich *Dunaliella* powder has been commercially exploited in many countries since the 1980s. Although many microalgae can produce xanthophylls, *H. pluvialis* is the one that accumulates them to the highest levels (e.g., asthaxanthin [10]), so it is now cultivated at large scale by several companies using distinct approaches [39]. On the other hand, *Muriellopsis* sp. holds a high lutein content (up to 35 mg Lƺ1), coupled with a high growth rate; hence, it has been exploited for commercial production of lutein [10]. Finally, *C. ellipsoidea* was reported to produce violaxanthin, together with two other minor xanthophylls, *viz*. antheraxanthin and zeaxanthin— whereas the main carotenoid in *C. vulgaris* was lutein [23]. Further pieces of related information are gathered in Table 1. 


**Table 1.** Carotenoids produced by selected microalgae. 
