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. 2022 Nov 3;27(21):7502.
doi: 10.3390/molecules27217502.

Post-Consumer Poly(ethylene terephthalate) (PET) Depolymerization by Yarrowia lipolytica: A Comparison between Hydrolysis Using Cell-Free Enzymatic Extracts and Microbial Submerged Cultivation

Julio Cesar Soares Sales  1 , Aline Machado de Castro  2 , Bernardo Dias Ribeiro  3 , Maria Alice Zarur Coelho  3
Affiliations

Post-Consumer Poly(ethylene terephthalate) (PET) Depolymerization by Yarrowia lipolytica: A Comparison between Hydrolysis Using Cell-Free Enzymatic Extracts and Microbial Submerged Cultivation

Julio Cesar Soares Sales et al. Molecules. .

Abstract

Several microorganisms have been reported as capable of acting on poly(ethylene terephthalate) (PET) to some extent, such as Yarrowia lipolytica, which is a yeast known to produce various hydrolases of industrial interest. The present work aims to evaluate PET depolymerization by Y. lipolytica using two different strategies. In the first one, biocatalysts were produced during solid-state fermentation (SSF-YL), extracted and subsequently used for the hydrolysis of PET and bis(2-hydroxyethyl terephthalate) (BHET), a key intermediate in PET hydrolysis. Biocatalysts were able to act on BHET, yielding terephthalic acid (TPA) (131.31 µmol L-1), and on PET, leading to a TPA concentration of 42.80 µmol L-1 after 168 h. In the second strategy, PET depolymerization was evaluated during submerged cultivations of Y. lipolytica using four different culture media, and the use of YT medium ((w/v) yeast extract 1%, tryptone 2%) yielded the highest TPA concentration after 96 h (65.40 µmol L-1). A final TPA concentration of 94.3 µmol L-1 was obtained on a scale-up in benchtop bioreactors using YT medium. The conversion obtained in bioreactors was 121% higher than in systems with SSF-YL. The results of the present work suggest a relevant role of Y. lipolytica cells in the depolymerization process.

Keywords: Biocatalysis; Yarrowia lipolytica; lipase; plastics.

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Conflict of interest statement

PETROBRAS has patent applications in this field.

Figures

Figure 1
Figure 1
Enzymatic hydrolysis of BHET using: (a) CALB and (b) SSF-YL and PC-PET using: (c) CALB and (d) SSF-YL at 37 °C and 180 rpm.
Figure 2
Figure 2
Growth of Y. lipolytica IMUFRJ 50682 in different media containing PET-PC (500 mg/L) at 28 °C and 250 rpm for 96 h.
Figure 3
Figure 3
Lipolytic activity during PC-PET biodepolymerization by submerged cultures of Y. lipolytica IMUFRJ 50682 at 28 °C and 250 rpm for 96 h.
Figure 4
Figure 4
Esterase activity during PC-PET biodepolymerization by submerged cultures of Y. lipolytica IMUFRJ 50682 at 28 °C and 250 rpm for 96 h.
Figure 5
Figure 5
Protease activity during PC-PET biodepolymerization by submerged cultures of Y. lipolytica IMUFRJ 50682 at 28 °C and 250 rpm for 96 h.
Figure 6
Figure 6
pH variations during PC-PET biodepolymerization by submerged cultures of Y. lipolytica IMUFRJ 50682 at 28 °C and 250 rpm for 96 h.
Figure 7
Figure 7
Hydrolysis products of PC-PET obtained during submerged cultivation of Y. lipolytica IMUFRJ 50682 in (a) YP, (b) YT, (c) YPD and (d) YTD medium at 28 °C and 250 rpm for 96 h.
Figure 8
Figure 8
ATR-FTIR spectrum before and after biodepolymerization during submerged cultures of Y. lipolytica IMUFRJ 50682 at 28 °C and 250 rpm for 96 h.
Figure 9
Figure 9
Y. lipolytica IMUFRJ 50682 growth and pH variation in the bioreactors (450 rpm, 1 vvm and 28 °C) containing YT medium + PC-PET (500 mg/L) over 96 h.
Figure 10
Figure 10
Enzymes production by Y. lipolytica IMUFRJ 50682 in bioreactors (450 rpm, 1 vvm and 28 °C) containing YT medium + PC-PET (500 mg/L) over 96 h.
Figure 11
Figure 11
PET hydrolysis products obtained during Y. lipolytica cultivation in bioreactors (450 rpm, 1 vvm and 28 °C) containing YT medium + PC-PET (500 mg/L) for 96 h.
Figure 12
Figure 12
ATR-FTIR spectrum before (black line) and after (red line) the biodepolymerization process during Y. lipolytica cultivation in bioreactors (450 rpm, 1 vvm and 28 °C) containing YT + PC-PET (500 mg/L) for 96 h.
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