## 8 Remediation Strategies and Methods
### Bioremediation  
Bioremediation is gaining attention for its advantages such as eco-friendliness, low cost, and low energy input. Basic categories for bioremediation are bacterial, fungal, and enzymatic degradations [179]. Chemical remediation techniques can also be combined with bioremediation because corrosion on the surface of MPs attracts microorganisms to be in these areas [245]. The usage of microorganisms to degrade MPs can be dependent on some parameters such as pH, temperature, and oxidative conditions [246]. By utilizing plastic fragments as the sole carbon source for energy and growth, recent technologies can be employed to predict the complete degradation and elimination of MPs [247]. The microbial degradation of plastic follows a series of steps. Firstly, biodeterioration occurs, which involves biological agents changing the physical and chemical properties of the polymer. This is followed by bio-fragmentation, where complex polymers are cleaved into simpler forms through the action of enzymes or acids. Microorganisms then incorporate these fragmented molecules through assimilation. Finally, the oxidized metabolites produced during degradation, such as CO\({}_{2}\), CH\({}_{4}\), and H\({}_{2}\)O, undergo mineralization [246; 247]. As mentioned earlier, UV radiation and photo-oxidation have been found to increase microbial degradation [248]. However, higher molecular weight plastic polymers pose a challenge due to their large fragments, which are difficult for microorganisms to take up. To overcome this, microorganisms employ two mechanisms: intracellular and extracellular degradation [249]. In intracellular degradation, microbes accumulate on the surface of MPs and hydrolyze the plastic into shorter chains whereas in extracellular degradation, bacteria secrete enzymes called hydrolases that break down complex polymers into simpler units, which can then be metabolized following which the mineralization process emerges. Fungal degradation also plays a crucial role in the biodegradation of plastics. Also, fungi enzymatically convert the metabolic intermediate into metabolic byproducts [208; 209]. Furthermore, there are some criteria to degrade MPs with fungal degradation which are surface area, molecular weight, hydrophilicity or hydrophobicity, crystallinity, functional groups, and chemical structure [210]. There are recent few attempts to use microalgae for the biodegradation of plastic. Exopolysaccharides (EPS) are synthesized by microalgae and enable them to colonize walls, rocks, and other substrates resulting in biodeterioration of the substrate. Surface charge, hydrophobicity, and electrostatic forces are the unique properties of EPS that bind to the substrate [250]. For example, the consortium of _Chlorella_ sp. and _Cyanobacteria_ sp. were found to deteriorate low-density polyethylene (LDPE sample), and this was confirmed by many chemical analyses like FTIR. The consortium was found to secrete various EPS. These EPS act as colonizing and degradative agents and convert polymers into monomers [251]. The factors that can affect the degradation process by microalgae include the type of polymer and the pre-treatment process such as UV, and heat. For instance, PP has raised severe environmental issues concerning its non-degradability. [PERSON] et al. investigated the ability of _Aspergillus terreus_ (ATCC 20542) and _Engyodontium album_ (BRIP 61534a) to break down PP and focused on the pre-treatment process. Polypropylene granule (GPP), film (FPP) and metallized film (MFPP) were pre-treated by either UV, heat, or [PERSON]'s reagent. _A. terreus_ incubated with UV-treated MFPP formed a high biomass yield. Additionally, surface morphological changes revealed consistent biodeterioration indication. Thus, _A. terreus_ and _E. album_ can grow on, change, and utilize PP as a source of carbon with pre-treatment aid, enhancing the biological pathways for plastic waste treatment [252]. Hydrolytic enzymes have been shown to be the major players in the biological degradation of polymers.