A Review of the Fungi That Degrade Plastic

Abstract

Plastic has become established over the world as an essential basic need for our daily life. Current global plastic production exceeds 300 million tons annually. Plastics have many characteristics such as low production costs, inertness, relatively low weight, and durability. The primary disadvantage of plastics is their extremely slow natural degradation. The latter results in an accumulation of plastic waste in nature. The amount of plastic waste as of 2015 was 6300 million tons worldwide, and 79% of this was placed in landfills or left in the natural environment. Moreover, recent estimates report that 12,000 million tons of plastic waste will have been accumulated on the earth by 2050. Therefore, it is necessary to develop an effective plastic biodegradation process to accelerate the natural degradation rate of plastics. More than 400 microbes have been identified as capable of plastic degradation. This is the first paper of the series on plastic-degrading fungi. This paper provides a summary of the current global production of plastic and plastic waste accumulation in nature. A list is given of all the plastic-degrading fungi recorded thus far, based on the available literature, and comments are made relating to the major fungal groups. In addition, the phylogenetic relationships of plastic-degrading fungi were analyzed using a combined ITS, LSU, SSU, TEF, RPB1, and RPB2 dataset consisting of 395 strains. Our results confirm that plastic-degrading fungi are found in eleven classes in the fungal phyla Ascomycota (Dothideomycetes, Eurotiomycetes, Leotiomycetes, Saccharomycetes, and Sordariomycetes), Basidiomycota (Agaricomycetes, Microbotryomycetes, Tremellomycetes, Tritirachiomycetes, and Ustilaginomy-cetes), and Mucoromycota (Mucoromycetes). The taxonomic placement of plastic-degrading fungal taxa is briefly discussed. The Eurotiomycetes include the largest number of plastic degraders in the kingdom Fungi. The results presented herein are expected to influence the direction of future research on similar topics in order to find effective plastic-degrading fungi that can eliminate plastic wastes. The next publication of the series on plastic-degrading fungi will be focused on major metabolites, degradation pathways, and enzyme production in plastic degradation by fungi.

Keywords: fungi; global plastic production; multi-gene phylogeny; plastic waste accumulation; synthetic polymers.

Figure 1

Phylogenetic relationships of plastic-degrading fungi. Phylogram generated from a maximum likelihood analysis of ITS, LSU, SSU, TEF, RPB1 and RPB2 fungal sequence data. MLBP values ≥ 70% and BYPP ≥ 0.90 values are given as the first and the second set of numbers near the nodes. Strain/culture numbers are given after the taxon names. The tree is rooted with Basidiobolus ranarum AFTOL-ID 301, Basidiobolus ranarum ARSEF 260, Basidiobolus ranarum ATCC 14449, and Olpidium brassicae AFTOL-ID 633. Strains in Red: Strains directly reported as plastic degraders. Green: Other strain of the same species reported as plastic degraders. Blue: Other species in the same genus reported as plastic degraders.

Figure 1

Phylogenetic relationships of plastic-degrading fungi. Phylogram generated from a maximum likelihood analysis of ITS, LSU, SSU, TEF, RPB1 and RPB2 fungal sequence data. MLBP values ≥ 70% and BYPP ≥ 0.90 values are given as the first and the second set of numbers near the nodes. Strain/culture numbers are given after the taxon names. The tree is rooted with Basidiobolus ranarum AFTOL-ID 301, Basidiobolus ranarum ARSEF 260, Basidiobolus ranarum ATCC 14449, and Olpidium brassicae AFTOL-ID 633. Strains in Red: Strains directly reported as plastic degraders. Green: Other strain of the same species reported as plastic degraders. Blue: Other species in the same genus reported as plastic degraders.

Figure 1

Phylogenetic relationships of plastic-degrading fungi. Phylogram generated from a maximum likelihood analysis of ITS, LSU, SSU, TEF, RPB1 and RPB2 fungal sequence data. MLBP values ≥ 70% and BYPP ≥ 0.90 values are given as the first and the second set of numbers near the nodes. Strain/culture numbers are given after the taxon names. The tree is rooted with Basidiobolus ranarum AFTOL-ID 301, Basidiobolus ranarum ARSEF 260, Basidiobolus ranarum ATCC 14449, and Olpidium brassicae AFTOL-ID 633. Strains in Red: Strains directly reported as plastic degraders. Green: Other strain of the same species reported as plastic degraders. Blue: Other species in the same genus reported as plastic degraders.

Figure 1

Phylogenetic relationships of plastic-degrading fungi. Phylogram generated from a maximum likelihood analysis of ITS, LSU, SSU, TEF, RPB1 and RPB2 fungal sequence data. MLBP values ≥ 70% and BYPP ≥ 0.90 values are given as the first and the second set of numbers near the nodes. Strain/culture numbers are given after the taxon names. The tree is rooted with Basidiobolus ranarum AFTOL-ID 301, Basidiobolus ranarum ARSEF 260, Basidiobolus ranarum ATCC 14449, and Olpidium brassicae AFTOL-ID 633. Strains in Red: Strains directly reported as plastic degraders. Green: Other strain of the same species reported as plastic degraders. Blue: Other species in the same genus reported as plastic degraders.

Figure 2

Compressed overview of the phylogram for the phylogenetic relationships of plastic-degrading fungi. Class level taxonomic ranks in Green include fungal species that were reported as plastic degraders.