Linking the Metabolic Activity of Plastic-Degrading Fungi to Their Taxonomy and Evolution

Abstract

Plastic, a ubiquitous part of our daily lives, has become a global necessity, with annual production exceeding 300 million tons. However, the accumulation of synthetic polymers in our environment poses a pressing global challenge. To address this urgent issue, fungi have emerged as potential agents for plastic degradation. In our previous manuscript, 'A Review of the Fungi That Degrade Plastic', we explored the taxonomic placement of plastic-degrading fungi across three main phyla: Ascomycota, Basidiomycota, and Mucoromycota. In this review, we built upon that foundation and aimed to further explore the taxonomic relationships of these fungi in a comprehensive and detailed manner, leaving no stone unturned. Moreover, we linked metabolic activity and enzyme production of plastic-degrading fungi to their taxonomy and summarized a phylogenetic tree and a detailed table on enzyme production of plastic-degrading fungi presented here. Microbial enzymes are key players in polymer degradation, operating intra-cellularly and extra-cellularly. Fungi, one of the well-studied groups of microbes with respect to plastic degradation, are at the forefront of addressing the global issue of plastic accumulation. Their unique ability to hydrolyze synthetic plastic polymers and produce a wide range of specific enzymes is a testament to their potential. In this review, we gather and synthesize information concerning the metabolic pathways of fungi involved in the degradation of plastics. The manuscript explores the diverse range of specific enzymes that fungi can produce for plastic degradation and the major pathways of plastic metabolism. We provide a listing of 14 fungal enzymes (Esterase, Cutinase, Laccase, Peroxidases, Manganese peroxidase, Lignin peroxidase, Oxidoreductases, Urease, Protease, Lipase, Polyesterase, Dehydrogenase, Serine hydrolase, and PETase) involved in pathways for plastic degradation alongside the relevant fungi known to produce these enzymes. Furthermore, we integrate the fungi's enzyme-producing capabilities with their taxonomy and phylogeny. Taxonomic and phylogenetic investigations have pinpointed three primary fungal classes (Eurotiomycetes, Sordariomycetes (Ascomycota), and Agaricomycetes (Basidiomycota)) as significant plastic degraders that produce the vital enzymes mentioned earlier. This paper provides a foundational resource for recognizing fungal involvement in the biodegradation of synthetic polymers. It will ultimately advance fungal biotechnology efforts to address the global issue of plastic accumulation in natural environments.

Keywords: depolymerization; energy source; enzymes; metabolic by-products; mineralization.

Figure 1

The phylogram was obtained from the data set provided by Ekanayaka et al. [2]. Branches are collapsed to show the genera of the kingdom Fungi. Fourteen columns on the right side of the figure include major fungal enzymes. The cells in each column are relevant to the fungal genera represented in the phylogram and are coloured accordingly when the fungal genera can produce enzymes. The literature summarized in Table 1 identifies each fungal genus’s capability to produce enzymes. Note: esterases, E; cutinases, C; lipases, L; laccases, Lac; peroxidases, Pero; manganese peroxidase, MnP; lignin peroxidase, LiP; oxidoreductases, Oxi; urease, U; protease, P; polyesterase, PE; dehydrogenase, DH; serine hydrolase, SeH; PETase, PET.

Figure 1

The phylogram was obtained from the data set provided by Ekanayaka et al. [2]. Branches are collapsed to show the genera of the kingdom Fungi. Fourteen columns on the right side of the figure include major fungal enzymes. The cells in each column are relevant to the fungal genera represented in the phylogram and are coloured accordingly when the fungal genera can produce enzymes. The literature summarized in Table 1 identifies each fungal genus’s capability to produce enzymes. Note: esterases, E; cutinases, C; lipases, L; laccases, Lac; peroxidases, Pero; manganese peroxidase, MnP; lignin peroxidase, LiP; oxidoreductases, Oxi; urease, U; protease, P; polyesterase, PE; dehydrogenase, DH; serine hydrolase, SeH; PETase, PET.