The ubiquitous persistence of plastic waste in diverse forms and different environmental matrices is one of the main challenges that modern societies are facing at present. The exponential utilization and recalcitrance of synthetic plastics, including polyethylene terephthalate (PET), results in their extensive accumulation, which is a significant threat to the ecosystem. The growing amount of plastic waste ending up in landfills and oceans is alarming due to its possible adverse effects on biota. Thus, there is an urgent need to mitigate plastic waste to tackle the environmental crisis of plastic pollution. With regards to PET, there is a plethora of literature on the transportation route, ingestion, environmental fate, amount, and the adverse ecological and human health effects. Several studies have described the deployment of various microbial enzymes with much focus on bacterial-enzyme mediated removal and remediation of PET. However, there is a lack of consolidated studies on the exploitation of fungal enzymes for PET degradation. Herein, an effort has been made to cover this literature gap by spotlighting the fungi and their unique enzymes, e.g., esterases, lipases, and cutinases. These fungal enzymes have emerged as candidates for the development of biocatalytic PET degradation processes. The first half of this review is focused on fungal biocatalysts involved in the degradation of PET. The latter half explains three main aspects: (1) catalytic mechanism of PET hydrolysis in the presence of cutinases as a model fungal enzyme, (2) limitations hindering enzymatic PET biodegradation, and (3) strategies for enhancement of enzymatic PET biodegradation.
PET Packaging Products | Global Consumption in 2020 (Million Tonnes) |
---|---|
Water Bottles | 7.02 |
Carbonated soft drink (CSD) bottles (e.g., Coca Cola, beers) | 7.02 |
Other drinks (e.g., juices, milk) | 4.86 |
Other bottles/containers in form of films and sheets | 3.78 |
Food containers | 2.43 |
Containers for non-food consumer products (e.g., cosmetics) | 1.62 |
Hazardous Additives | Chemical Formula | Chemical Structure | Toxic Effects | References |
---|---|---|---|---|
Bisphenol A (BPA) |
C15H16O2 |
Female and male infertility Precocious puberty Breast cancer Prostate cancer Metabolic disorders including polycystic ovary syndrome (PCOS) |
[39] | ||
Bis (2-ethylhexyl) phthalate (DEHP) | C24H38O4 |
Cancer Reproductive system Stages of development Nerve system Immune system |
[40] | ||
Benzyl butyl phthalate (BBP) |
C19H20O4 |
Decrease in thyroid hormone levels Endocrine system Stages of development Reproductive system |
[41] | ||
Lead chromate molybdate sulphate red | Pb(Cr,Mo, S)O4 |
Cardiovascular system Respiratory system Gastrointestinal-liver Endocrine system Cancer Kidney damage Neurotoxic effects |
[42] | ||
Medium-chain chlorinated paraffins (MCCP) |
C14H24Cl6 |
Skin dryness Adverse effects on aquatic life |
[43] | ||
Triclosan | C12H7Cl3O2 |
Thyroid hormones Reproductive system Breast cancer |
[44] | ||
Dibutyl phthalate (DBP) |
C6H4(CO2C4H9)2 |
Effect on kidney Reproductive system Irritation of eyes, nose, throat, and skin |
[42] | ||
Diisobutyl phthalate (DiBP) |
C16H22O4 |
Reproductive system Developmental system Liver Kidney Possible triggering of cancer |
[45] | ||
Dicyclohexyl phthalate (DCHP) |
C20H26O4 |
Reproductive system Cumulative anti-androgenic effect with other phthalates |
[46] | ||
Tris(2-chloroethyl)phosphate (TCEP) |
C6H12Cl3O4P |
Possible impairment of fertility Adverse effects on aquatic organisms |
[47] | ||
1,3,5-Tris(oxiran-2-ylmethyl)-1,3,5-triazinane-2,4,6-trione (TGIC) |
C12H15N3O6 |
If swallowed If inhaled May cause genetic defects Serious eye damage |
[42] | ||
1,3,5-tris[(2S and 2R)-2,3-epoxypropyl]-1,3,5-triazine-2,4,6- (1H,3H,5H)-trione (β-TGIC) |
C24H30N6O12 |
May cause genetic defects Harmful if swallowed Causes serious eye damage May cause damage to organs through prolonged or repeated exposure May cause an allergic skin reaction |
[42] | ||
Bisphenol S | C12H10O4S |
Obesity Metabolic disorders Possible triggering of cancer Reproductive defects Gestational diabetes Breast cancers |
[48] | ||
Benzophenone-3 | C14H12O3 |
Allergic reactions Endocrine disruption Hirschsprung’s disease |
[49] | ||
Antimony trioxide | Sb2O3 |
Possible triggering of lung cancer Reproductive system Kidney, liver, heart |
[50] |
This entry is adapted from the peer-reviewed paper 10.3390/jof7110931