Construction of an MRCUT1 Cutinase-Expressing Saccharomyces boulardii Probiotic Yeast Strain Capable of Degrading Polyethylene Terephthalate (PET) Microplastics

Excessive use of plastics has led to an unprecedented global accumulation of plastic waste, particularly of the polyethylene terephthalate (PET) polymer, resulting in severe environmental and health challenges due to the proliferation of microplastic particles. To respond to this environmental challenge, especially in the Philippines, where single-use plastic sachet pollution is rampant, we genetically engineered Saccharomyces boulardii yeast cells to express and secrete the cutinase enzyme (MRCUT1) derived from the fungus Moniliophthora roreri. Our results suggest that our engineered yeast can degrade pre-weighed PET fragments over a twenty-one-day period in vitro, with significant measurable weight reductions observed within the first week of incubation. Statistical analysis (One-way ANOVA, p = 0.0112) confirmed that our MRCUT1 engineered strain degraded PET at a significantly higher rate than non-engineered control cells. To the best of our knowledge, this is the first time that a cutinase capable of PET degradation has been successfully expressed in and secreted by yeast. It also opens up the possibility that our MRCUT1-expressing probiotic could be used prophylactically to mitigate the microplastic bioaccumulation in the gastrointestinal tracts of common food fish like the rabbitfish (Siganus fuscescens) and the milkfish (Chanos chanos), both of which are popular aquaculture fish in the Philippines.