Distinct microbial communities degrade cellulose diacetate bioplastics in the coastal ocean

Abstract

Cellulose diacetate (CDA) is a bio-based plastic widely used in consumer products. CDA is a promising alternative to conventional thermoplastics due to its susceptibility to biodegradation in various environments. Despite widespread evidence for the degradation of CDA, relatively little is known about the microorganisms that drive degradation, particularly in the ocean. Recently, we documented the biodegradation of CDA-based materials (i.e., fabric, film, and foam) in a continuous-flow natural seawater mesocosm on the timescales of months, as indicated by mass loss, enzyme activity, and respiration to carbon dioxide. These findings paved the way for the present study aimed at identifying key microbial taxa implicated in CDA degradation. Analysis based on 16S rRNA gene amplicon sequencing of bacteria and archaea revealed that material type, incubation time, material morphology (e.g., fabric vs film), and plasticizer content significantly influenced the microbial community structure. Differential abundance analysis revealed that bacterial taxa affiliated with the families of Arenicellaceae , Cellvibrionaceae , Methyloligellaceae , Micavibrionaceae , Puniceicoccaceae , Spirosomaceae , and Thermoanaerobaculaceae , and the order of Pseudomonadales potentially initiated the degradation (i.e., deacetylation) of CDA fabric and film. These taxa were notably distinct from CDA-degrading microbes reported in non-seawater environments. Collectively, the findings lend further support for CDA as a promising next-generation, high-utility, and low-environmental persistence bioplastic material. IMPORTANCE Cellulose diacetate (CDA) is a promising alternative to conventional plastics due to its versatility in manufacturing and low environmental persistence. Previously, our group demonstrated that CDA is susceptible to biodegradation in the ocean on timescales of months. In this study, we report the composition of microorganisms driving CDA degradation in the coastal ocean. We found that the coastal ocean harbors distinct bacterial taxa implicated in CDA degradation and these taxa have not been previously identified in prior CDA degradation studies, indicating an unexplored diversity of CDA-degrading bacteria in the ocean. Moreover, the shape of the plastic article (e.g., a fabric, film, or foam) and plasticizer in the plastic matrix selected for different microbial communities. Our findings pave the way for future studies to identify the specific species and enzymes that drive CDA degradation in the marine environment, ultimately yielding a more predictive understanding of CDA biodegradation across space and time.

Strategies to Reduce the Environmental Lifetimes of Drinking Straws in the Coastal Ocean

“…In contrast, the PLA and PP straws, which did not measurably degrade, had similar community structures despite having vastly different material types (i.e., polyester vs polyolefin). This result suggests that these materials only provided surfaces for the colonization of microorganisms rather than substrates for metabolism, an observation consistent with our previous findings …”

“…This assumption is reasonable for CDA, PHA, and paper materials because it is well established that these materials biodegrade to CO 2 in the coastal ocean. , Moreover, our previous research on CDA showed that mass loss rates were comparable to respiration rates . Consistent with the absence of waves and abrasives (e.g., sand) in our study system, no mass loss has been detected in sterilized controls . Additionally, because biodegradation is a surface-driven process, if any mass loss were attributed to physical disintegration (fragmentation), then this would only increase the fragments’ surface area and thus mass loss (eq ) and respiration rates.…”

“…The white color of the foamed straw is due to internal reflections because of the pores. Further details on both CDA straws can be found in their technology’s published patents. , The CDA formulation used in both straws was the same as in our previous studies focused on CDA degradation; − the degree of substitution was 2.4, and the number-average molecular weight was approximately 90 kDa. According to the manufacturers, the Phade and Beyond Green straws were made from Nodax, a PHA produced by Danimer Scientific, and met several biodegradation standards for industrial compostability (ASTM D6400), home compostability (ISO 20200 and ISO 14855), and marine degradability (ASTM D6691).…”

“…All samples were subjected to DNA extraction using a DNeasy PowerBiofilm kit (Qiagen, Catalog #24000-50) according to the manufacturer’s protocol. Amplicon libraries for variable region V4 were prepared following previously established procedures. , The pooled amplicon libraries were sequenced using a 2 × 250 bp MiSeq platform (Illumina) at the Institute for Genome Sciences at the University of Maryland. Amplicon reads were processed in R (4.0.2) using the DADA2 (1.16) pipeline for quality control, merging sequences, and assigning amplicon sequence variants (ASVs).…”

Foaming enables material-efficient bioplastic products with minimal persistence

“…Foaming biodegradable bioplastics may solve these conflicting outcomes of widely used plastic foams. Several biodegradable bioplastics, such as cellulose diacetate (CDA) [18][19][20][21] , have been shown to biodegrade in natural environments (soil, freshwater, and seawater) on timescales of months to years 22 . The degradation of plastics in the environment is a surface-driven process that depends on the surface area-to-volume ratio (SA/V) of the item and the specific surface degradation rate of the material (𝑘 𝑑 ) 23 .…”