Evaluation of low-density polyethylene biodegradation by Bacillus safensis BS-10L after plasma treatment under environmental stress and underlying mechanisms

The decomposition efficiency of bacterial plastic biodegradation methods remains inadequate, resulting in long degradation times. The use of Bacillus safensis BS-10L, a low-density polyethylene (LDPE)-degrading strain, with plasma can improve plastic degradation. However, maintaining LDPE-degradation efficiency and bacterial vitality remains challenging. Here, we aimed to evaluate whether the plasma-enhanced activity and functional capacity of B. safensis are maintained under environmental stress and to identify key factors associated with microbial activation. We further assessed antioxidant activity to determine microbial stress resistance and the effect of plasma treatment on microbial peroxide defense. Treatment with dielectric-barrier discharge plasma increased the activity of microbial peroxide detoxification enzymes more than two-fold and the expression of the transcription factor PerR five-fold. Factors influencing microbial activation in plasma under atmospheric pressure were categorized into physical and chemical parameters. The strongest microbial activation was observed under conditions in which physical parameters, such as UV light, and chemical parameters, such as active species, coexisted. Furthermore, electron spin resonance analysis showed the strongest microbial activation under conditions in which short-lived species, such as singlet oxygen, coexisted with physical parameters. Overall, plasma treatment enhanced the stress tolerance and LDPE-degrading activity of B. safensis BS-10L, with a 3-min exposure markedly increasing antioxidant responses and maintaining film oxidation under drought and salinity stress. These findings reveal key factors relevant to plasma activation and highlight BS-10L as a promising candidate for environmentally safe plastic bioremediation.