Production of PETase by engineered Yarrowia lipolytica for efficient poly(ethylene terephthalate) biodegradation.

There has been a growing interest in poly(ethylene terephthalate) PET degradation studies in the last few years due to its widespread use and large-scale plastic waste accumulation in the environment. One of the most promising enzymatic methods in the context of PET degradation is the use of PETase from Ideonella sakaiensis, which has been reported to be an efficient enzyme for hydrolysing ester bonds in PET. In our study, we expressed a codon-optimized PETase gene in the yeast Yarrowia lipolytica. The obtained strain was tested for its ability to degrade PET directly in culture, and a screening of different supplements that might raise the level of PET hydrolysis was performed. We also carried out long-term cultures with PET film, the surface of which was examined by scanning electron microscopy. The efficiency of PET degradation was tested based on the concentration of degradation products released, and the results showed that supplementation of the culture with olive oil resulted in 66 % higher release of terephthalic acid into the medium compared to the mutant culture without supplementation. The results indicate the possibility of ethylene glycol uptake by both strains, and, additionally, the PETase produced by the newly engineered strain hydrolyses MHET. The structure of the PET film after culture with the modified strain, meanwhile, had numerous surface defects, cracks, and deformations.

Metabolic engineering of Yarrowia lipolytica for poly(ethylene terephthalate) degradation.

Polyethylene terephthalate (PET) is the most widely used plastic, whose global production scale causes serious problems due to it being highly non-biodegradable. The present work provides a novel approach to plastic degradation studies, which involves direct degradation of PET in the culture of a modified Y. lipolytica yeast strain extracellularly producing cutinase from Fusarium solani. In this study, we successfully accomplished a scale-up of the degradation process in culture, which is promising from the perspective of wider application of the developed method in the future. Additionally, we tested the effect of various supplements, which may increase the PET degradation efficiency in the culture of the Y. lipolytica pAD CUT_FS strain. The ability of PET decomposition was verified by the amount of the released degradation products, such as terephthalic acid (TPA) and mono-(2-hydroxyethyl)-terephthalic acid (MHET), during cultivation. We observed that the quantities of TPA and MHET released during the PET degradation process were increasing daily, and were 1.51 gL-1 and 0.45 gL-1, respectively after 240 h of the bioreactor fermentation. Analysis of the PET film by electron microscopy indicated that there was abundant damage on the surface of the material. This study also demonstrated that the engineered Y. lipolytica strain is able to degrade PET at 28 °C during fermentation. The results obtained in this study using amorphous PET powder provide a wide range of possibilities for application of the cutinase-secreting strain of Y. lipolytica on the more difficult to degrade highly crystalline PET films, PET bottles and PET melts.

Efficient conversion of crude glycerol from various industrial wastes into single cell oil by yeast Yarrowia lipolytica.

In this study, crude glycerol from various industries was used to produce lipids via wild type Yarrowia lipolytica A101. We tested samples without any prior purification from five different waste products; each contained various concentrations of glycerol (42-87%) as the sole carbon source. The best results for lipid production were obtained for medium containing glycerol from fat saponification. This reached 1.69gL(-1) (25% of total cell dry weight) with a biomass yield of 0.17gg(-1) in the flasks experiment. The batch cultivation in a bioreactor resulted in enhanced lipid production-it achieved 4.72gL(-1) with a biomass yield 0.21gg(-1). Moreover, the properly selected batch of crude glycerol provides a defined fatty acid composition. In summary, this paper shows that crude glycerol from soap production could be efficiently converted to single cell oil without any prior purification.