Kinetics of the polymerization of methylhydroquinone diacetate, terephthalic acid and poly(ethylene-terephthalate)

Poly(ethylene terephthalate) fabrics are treated with sodium hydroxide using ethylene glycol or glycerin as the solvent. Compared with conventional aqueous alkaline hydrolysis, the degradation rate in ethylene glycol increases tenfold. The kinetics of the alkaline-ethylene glycol treatment show that the weight loss is linear with respect to time. The moisture regain rate and tensile properties of the treated fabrics are measured; other tests include scanning electron microscopy and dyeing properties. The results show that the properties of the treated fabrics do not depend significantly on the solvent; therefore, using ethylene glycol can greatly shorten the treatment time to achieve results similar to those with the conventional aqueous system.

Download Full-text

Development of a targeted gene disruption system in the PET-degrading bacterium Ideonella sakaiensis and its applications to PETase and MHETase genes

Applied and Environmental Microbiology ◽

10.1128/aem.00020-21 ◽

2021 ◽

Author(s):

Shin-ichi Hachisuka ◽

Tarou Nishii ◽

Shosuke Yoshida

Keyword(s):

Terephthalic Acid ◽

Parent Strain ◽

Gene Disruption ◽

Ethylene Terephthalate ◽

Targeted Gene Disruption ◽

Degrading Bacterium ◽

Poly Ethylene Terephthalate ◽

Poly Ethylene ◽

Pet Hydrolase

Poly(ethylene terephthalate) (PET) is a commonly used synthetic plastic; however its non-biodegradability results in a large amount of waste accumulation that has a negative impact on the environment. Recently, a PET-degrading bacterium Ideonella sakaiensis 201-F6 strain was isolated and the enzymes involved in PET-digestion, PET hydrolase (PETase) and mono(2-hydroxyethyl) terephthalic acid (MHET) hydrolase (MHETase), were identified. Despite the great potentials of I. sakaiensis in bioremediation and biorecycling, approaches to studying this bacterium remain limited. In this study, to enable the functional analysis of PETase and MHETase genes in vivo , we have developed a gene disruption system in I. sakaiensis . The pT18 mobsacB -based disruption vector harboring directly connected 5'- and 3'-flanking regions of the target gene for homologous recombination was introduced into I. sakaiensis cells via conjugation. First, we deleted the orotidine 5'-phosphate decarboxylase gene ( pyrF ) from the genome of the wild-type strain, producing the Δ pyrF strain with 5-fluoroorotic acid (5-FOA) resistance. Next, using the Δ pyrF strain as a parent strain, and pyrF as a counterselection marker, we disrupted the genes for PETase and MHETase. The growth of both Δ petase and Δ mhetase strains on terephthalic acid (TPA, one of the PET hydrolytic products) was comparable to that of the parent strain. However, these mutant strains dramatically decreased the growth level on PET to that on no carbon source. Moreover, the Δ petase strain completely abolished PET degradation capacity. These results demonstrate that PETase and MHETase are essential for I. sakaiensis metabolism of PET. IMPORTANCE The poly(ethylene terephthalate) (PET)-degrading bacterium Ideonella sakaiensis possesses two unique enzymes able to serve in PET hydrolysis. PET hydrolase (PETase) hydrolyzes PET into mono(2-hydroxyethyl) terephthalic acid (MHET) and MHET hydrolase (MHETase) hydrolyzes MHET into terephthalic acid (TPA) and ethylene glycol (EG). These enzymes have attracted global attention as they have potential to be used for bioconversion of PET. Compared to many in vitro studies including the biochemical and crystal structure analyses, few in vivo studies have been reported. Here, we developed a targeted gene disruption system in I. sakaiensis , which was then applied for constructing Δ petase and Δ mhetase strains. Growth of these disruptants revealed that PETase is a sole enzyme responsible for PET degradation in I. sakaiensis , while PETase and MHETase play essential roles in its PET assimilation.

Download Full-text