Computational Exploration of Bio-Degradation Patterns of Various Plastic Types

Abstract

Plastic materials are recalcitrant in the open environment, surviving for longer without complete remediation. The current disposal methods of used plastic material are inefficient; consequently, plastic wastes are infiltrating the natural resources of the biosphere. The mixed composition of urban domestic waste with different plastic types makes them unfavorable for recycling; however, natural assimilation in situ is still an option to explore. In this research work, we have utilized previously published reports on the biodegradation of various plastics types and analyzed the pattern of microbial degradation. Our results demonstrate that the biodegradation of plastic material follows the chemical classification of plastic types based on their main molecular backbone. The clustering analysis of various plastic types based on their biodegradation reports has grouped them into two broad categories of C-C (non-hydrolyzable) and C-X (hydrolyzable). The C-C and C-X groups show a statistically significant difference in their biodegradation pattern at the genus level. The Bacilli class of bacteria is found to be reported more often in the C-C category, which is challenging to degrade compared to C-X. Genus enrichment analysis suggests that Pseudomonas and Bacillus from bacteria and Aspergillus and Penicillium from fungi are potential genera for the bioremediation of mixed plastic waste. The lack of uniformity in reporting the results of microbial degradation of plastic also needs to be addressed to enable productive growth in the field. Overall, the result points towards the feasibility of a microbial-based biodegradation solution for mixed plastic waste.

Keywords: bio-cycling; computational study; microbial degradation; mixed plastic waste; plastic waste.

Figure 1

The hierarchical classification of plastic types based on atomic composition of the main backbone.

Figure 2

The frequency plot for different plastic types based on the number of publications reported for biodegradation of the corresponding plastics type.

Figure 3

(a): Hierarchical clustering plot of plastic type cosine distance matrix computed from genus plastic association matrix. (b): Non-metric multidimensional scaling (NMDS) plot of cosine distance matrix computed from genus plastic association matrix where blue diamonds and red circles represent C-X and C-C types of plastics, respectively.

Figure 4

The heatmap shows the group level proportion plastic types reported for 51 selected genera. The left-most vertical bar shows the class of genus and the right-most bar shows the group association with individual rows if applicable.