# Effect of Agricultural Beneficial Microbes on the Degradability of Polylactic Acid Film in the Farmland Environment

## TL;DR

This study shows that three agricultural microbes significantly speed up the breakdown of biodegradable polylactic acid (PLA) films used in farming.

## Contribution

The study identifies specific microbes that enhance PLA degradation in farmland and explains how they alter soil microbial communities.

## Key findings

- PLA film degradation exceeded 30% in the presence of Trichoderma harzianum, Bacillus cereus, and Pseudomonas fluorescens.
- Microbes caused surface cracking of PLA films and reduced their molecular weight.
- The microbes increased Betaproteomicrobes abundance, promoting PLA breakdown.

## Abstract

Three common agricultural beneficial microbes, Trichoderma harzianum, Bacillus cereus, and Pseudomonas fluorescens, are widely used in the growth cycle of crops, and increase the yield of agricultural products through disease prevention and sterilization. As a biodegradable biological macromolecular material, polylactic acid (PLA) is also widely used in agricultural production as a biodegradable film. The addition of agricultural microbes will affect the degradation rate of polylactic acid and thus its agricultural use. Under specific conditions (Tri15), the degradation rate of PLA film exceeds 30%. Scanning electron microscopy (SEM) images show that the degradation of the PLA happened after 360 days of exposure to these three specific microbe environments, which makes the surface of PLA films crack. Gel permeation chromatography (GPC) analysis reveals that in the presence of these microbes, the molecular weight of PLA is reduced. The analysis of 16S rDNA sequences demonstrates that the introduction of these microbes alters the soil microbial community, resulting in an enhanced abundance of Betaproteomicrobes, promoting the degradation of PLA. These results indicate that the three microbes species significantly promote the degradation of PLA, and the effects of microbes vary for the different concentrations. This study establishes practical guidelines for the deployment of PLA in real-world farmland environments.