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The microbial response to biodegradable polylactic acid microplastics during anaerobic fermentation of waste

Jie Chen1, Jinjing Xiang1, Maoli Hu1

  • 1Key Laboratory of the Three Gorges Reservoir Region's Eco-environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing, 400045, China.

Environmental Research
|February 4, 2026
PubMed

Insights

Polylactic acid microplastics (MPs) in wastewater sludge inhibit volatile fatty acid (VFA) production by affecting enzymes and microbial communities. This impacts waste activated sludge (WAS) treatment efficiency.

Area of Science:

  • Environmental Science
  • Microbiology
  • Biotechnology

Background:

  • Microplastic (MP) accumulation in natural environments poses ecological risks.
  • Wastewater treatment plants (WWTPs) are significant MP accumulation sites.
  • The impact of biodegradable MPs like polylactic acid (PLA) on anaerobic sludge digestion is not well understood.

Purpose of the Study:

  • To investigate the effects of PLA MPs on volatile fatty acid (VFA) production during waste activated sludge (WAS) anaerobic fermentation.
  • To analyze the influence of PLA MPs on sludge solubilization, extracellular polymeric substances (EPS), enzymatic activities, oxidative stress, and microbial community structure.

Main Methods:

  • Exposure of WAS to varying concentrations of PLA MPs (0-200 particles/g-TS).
  • Measurement of VFA production and sludge solubilization.
  • Analysis of EPS structure, enzymatic activity, and lactate dehydrogenase (LDH) leakage.
  • Characterization of microbial community structure using 16S rRNA gene sequencing.

Main Results:

  • PLA MPs significantly inhibited VFA production, decreasing yields by 5.14-18.18%.
  • Sludge solubilization increased by 2.3-11.91% in the presence of PLA MPs.
  • PLA MPs inhibited key enzymatic activities, increased oxidative stress (39.9% LDH leakage), and altered microbial communities (reduced Bacteroidota).

Conclusions:

  • Biodegradable PLA MPs negatively impact anaerobic fermentation efficiency in WAS treatment.
  • Mechanisms include enzyme inhibition, increased oxidative stress, and unfavorable shifts in microbial communities.
  • Mitigation strategies are needed for WWTPs facing increasing biodegradable MP contamination.
Keywords:
Anaerobic fermentationBiodegradable plasticsPLAResource recoveryWaste activated sludge

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