## 2 Pharmaceuticals and Personal Care Products (PPCPs) in the Ecosystems
### Microbial Remediation in Culture
#### 2.1.3 Phycoremediation  
Traditionally, microalgae cultures have not been used for the elimination of PPCPs since these compounds are often toxic to photosynthetic organisms (e.g., [220, 221, 222]). In fact, some of them are used as ecotoxicity testing organisms due to their sensitiveness to pollutants (Table 1). This is probably the reason why, so far this century, only 52 manuscripts have been published using these microorganisms as PPCPs-removers and only 7% of them propose an important role in advanced biorecovery systems for microalgae (Figure 3C). _Scenedesmus obliquus_ and _Chlamydomonas mexicana_ have some capacity to eliminate CBZ at low concentrations, but higher concentrations inhibited algal growth [223]. IBU stimulated the algal growth of _Navicula_ sp. at lower concentrations, but growth decreased substantially at high concentrations (Figure 4). In addition, the inoculation of _Navicula_ sp. to water systems, can inhibit the degradation of IBU, implying that it could prolong the stress time by this anti-inflammatory drug [224]. However, using wastewater as a source of nitrogen and phosphorus for mass production of rich added-value microalgae with the simultaneous contaminant removal represents an extraordinarily attractive option. Overall, the energy (biogas and biodiesel), pharmaceutical, food and feed industries are an attractive market of microalgae applications (Figure 4, [225, 226, 227, 228]). In fact, estimations for demand in microalgae products project an increase up to US$ 44.6 billion by 2023 [227, 229]. Recently, a geographic information system model was built to identify the areas in Mexico with high potential for microalgae production [227]. Some studies have shown that algal treatments of wastewater considerably reduce a high number of PPCPs (Figure 3C), but the toxicity of the water persists, due to the presence of ammonium, a metabolism toxic derivative, [99; 234; 235]. Although in some analyzes, on a laboratory scale, this toxic compound has been eliminated [103], the number of laboratory tests should be increased in order to confirm these results. Most of the focuses mainly on studies in continuous open ponds (e.g., [236; 237]). As far as we know, the PPCPs algae-removal mechanisms are like those described for bacteria and fungi: intracellular and extracellular biodegradation, bioadsorption or/and bioaccumulation, (Figure 2, [238]). Extracellular processes appear to be mediated by lacases, like fungi and bacteria. Thus, _Tetracystis_ lacase converts bisphenol A, 17\(\alpha\)-ethinylestradiol, NP and TCS in the presence of a redox mediator [102]. The intracellular degradative metabolic pathway would be mediated by cytochrome P450 and conjugation with the implication of several other enzymes [223], Figure 2). External digestion could be carried out by lacases and other extracellular enzymes [102; 103]. Metabolic pathways for phycodegradation of SMT and SMX have been proposed elsewhere [239]. The degradation of these antibiotics was higher at higher concentrations, indicating that biodegradation might be an efficient mechanism of microalgae acclimatization to antibiotics [240]. _Desmodesmus subpictatus_ uptake and biotransformation E2\(\alpha\) but yields a very toxic brominated product [241]. Green algae _Desmodesmus_ sp. and _Scenedesmus obliquus_ were used to carry out hydrolysis and reductive dechlorination of TCS, suggesting the possibility of mineralization by these algae [38]. Similarly, [242] not only report the bioremediation of DFC using _Chorella sorokiniana_, _Chorella vulgaris_ and _Scenedesmus obliquus_, but also show an important reduction in the toxicity of the effluents, especially with _S. obliquus_. Even non-living _S. obliquus_ can be an effective option in the elimination of DFC and other PPCPs by bioadsorption [243; 244] since pollutants with cationic groups are actively attracted to the cell wall through electrostatic interactions [238]. Figure 4: Towards the circular supply chain management (CSCM) reactivation. **a**.