Bacterial degradation of a new polyester,polyethylene glycol-phthalate polyester

Microorganisms which can assimilate a new polyester synthesized from polyethylene glycol (PEG) as a dihydroxyl compound and phthalic acid as a dicarboxyl compound were isolated from soils by enrichment culture techniques. Two cultures, K and N, were obtained: Culture K grew on PEG 4000 polyester and culture N assimilated PEG 6000 polyester. Each culture included two bacteria indispensable for the degradation of polyesters: bacteria K1 and K2 for PEG 4000 polyester-utilizing culture K and bacteria N1 and N2 for PEG 6000 polyester-utilizing culture N. Bacteria K2 and N2 were responsible for the hydrolysis of ester bonds in a polyester and both were identified as the same species,Comamonas acidovorans. Bacteria K1 and N6 could assimilate PEG as a sole carbon and energy source. Both are Gram-negative, non-spore-forming rods and resembled each other on their colony characteristics, although strain K1 could not grow on PEG 6000.C. acidovorans N2 (K2) grew on dialkyl phthalates (C₂–C₄) and phthalate and tributyrin, but not on PEG, diphthalic PEG, and PEG phthalate polyesters. Their culture supernatant and washed cells hydrolyzed PEG (400–20,000) phthalate and sebacate polyesters.C. acidovorans had higher esterase activity toward PEG phthalate, isophthalate, and terephthalate polyesters than known esterase and lipases. The esterase seemed to be an extracellular one and attached to the cell surface.     

Comparative Biodegradation Studies of Non-poronized and Poronized LDPE Using Indigenous Microbial Consortium

Seventeen bacterial isolates were screened for the utilization of low density polyethylene (LDPE) as the sole carbon source, out of which five potential strains were selected for the development of a consortium. In vitro biodegradation efficiency of the consortium was studied for two differently textured forms of LDPE viz. non-poronized and poronized. Although, both the forms were acted-upon well by the consortium, but the degradation was found to be better in the poronized form. This was substantiated by λ-max shift, FTIR spectra and simultaneous TG-DTG-DTA. The analysis revealed the breakage and formation of chemical bonds in the polymer backbone, as a result of microbial activity. The biodegraded samples of non-poronized and poronized LDPE exhibited similar weight losses at 400 °C (24.12% and 24.48%, respectively) as compared to their controls (4% and 4.5% respectively), but the latter could achieve it with greater ease as reveled by its lower heat of reactions (ΔH values). The study signifies the influence of poronization of polyethylene on its rate of biodegradation.     

A Sensitive Electrochemical Impedance Spectroscopy Method for Detection of Polyimide Degradation by Microorganisms

An electrochemical impedance spectroscopy (EIS) technique was evaluated for monitoring microbial degradation of electronic packaging polyimides. The microbial inoculum was a mixed culture of fungi isolated previously from deteriorated polyimides. The active fungal consortium comprised Aspergillus versicolor, Cladosporium cladosporioides, and a Chaetomium species. After inoculation, fungal growth on the polyimides resulted in distinctive EIS spectra indicative of polymer insulation failure, which directly related to polymer integrity. Degradation appeared to occur in a number of steps and two distinctive stages in the decline of film resistance were observed in the inoculated EIS cells within the 2 and 10 weeks after inoculation. The early stage of resistance decrease may be related to the ingress of water molecules and ionic species into the polymeric materials, whereas the second stage probably resulted from partial degradation of the polymers by fungal growth on the polymer film. The relationship between changes of impedance spectra and microbial degradation of the polymer was further supported by scanning electron microscopy (SEM) observations of fungi growing on the surface of the inoculated polyimides. Our data indicate that the EIS can be used in detection of early degradation of resistant polymers and polyimides that are susceptible to biodeterioration.     

A test method to determine rapidly if polymers are biodegradable

Polycaprolactone and polycaprolactone/polyethylene blends were exposed to two consortia, one containing three fungi (Aspergillus niger, Gliocladium virens, andPenicillium funiculosum) and one five fungi (the three aforementioned plusAureobasidium pullulans andChaetomium globosum). Evidence of metabolization of the polymer by the five-fungus consortium was obtained from the greater oxygen consumption in the presence of polycaprolactone than in the absence of the polymer. Minor differences in the composition of the consortium result in major differences in the ability of the consortium to utilize the polymer as a carbon source.Certain commercial products are identified in order adequately to specify experimental procedures. In no case does such identification imply endorsement by the National Institute of Standards and Technology or that the material is necessarily the best available for the purpose.     

Sorption of strontium on bentonite

Sorption of Sr on bentonite was studied using the batch technique. Distribution coefficients (K_d) were determined as a function of contact time, pH, sorbent and sorbate concentration and temperature. The data were interpreted in terms of Freundlich, Langmuir and Dubinin-Radushkevich isotherms. Thermodynamic parameters for the sorption system were determined at three different temperatures. The positive value of the heat of sorption, ΔH° = 30.62 kJ/mol at 298 K, shows that the sorption of strontium on bentonite is endothermic. The negative value of the free energy of sorption, ΔG° = −10.69 kJ/mol at 298 K, shows the spontaneity of the reaction. ΔG° becomes more negative with increasing temperature, which shows that the sorption process is more favorable at higher temperatures. The mean free energy for sorption, E 9 kJ/mol, suggests that ion exchange is the predominant mode of sorption in the Sr concentration range studied, i.e. 0.01 – 0.3 mol/dm³. The presence of complementary cations depresses the sorption of strontium on bentonite in the order Ca²⁺>Mg²⁺>K⁺>Na⁺. Some organic complexing agents and natural ligands also affect the sorption of strontium. The desorption studies with ground water at low strontium loadings on bentonite show that about 90% of Sr is irreversibly sorbed on the bentonite.     

Degradation of Poly(3-hydroxybutyrate) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by Some Soil Aspergillus spp.

Systematic screening of 45 soil fungi for degradation polyhydroxyalkanoic acids (PHAs) has led to the selection of 6 potent Aspergillus isolates belonging to A. flavus, A. oryzae, A. parasiticus, and A. racemosus. Degradation of PHAs as determined by tube assay method revealed that these Aspergillus spp. were more efficient in degrading poly(3-hydroxybutyrate) [P(3HB)] compared to copolymer of 3-hydroxybutyric acid and 3-hydroxyvaleric acid (P3HB-co-16% 3HV). Moreover, the extent of degradation in mineral base medium was much better than those in complex organic medium. For all the Aspergillus spp. tested, maximum degradation was recorded at a temperature of 37°C with significant inhibition of growth. The optimum pH range for degradation was 6.5–7.0 with degradation being maximum at pH 6.8. The extent of polymer degradation increased with increase in substrate concentration, the optimum concentration for most of the cultures being 0.4% and 0.2% (w/v) for P(3HB) and P(3HB-co-16%3HV) respectively. Supplementation of the degradation medium with additional carbon sources exerted significant inhibitory effect on both P(3HB) and P(3HB-co-16%3HV) degradation.     

Anaerobic microbial degradation of poly (3-hydroxyalkanoates) with various terminal electron acceptors

The microbial degradation of poly (3-hydroxyalkanoates) (PHAs) under anaerobic conditions with various terminal electron acceptors was examined. Nitrate-reducing consortia were established using activated sludge, and PHAs were shown to be biodegradable under these conditions. A positive correlation between carbon dioxide production and nitrate reduction was demonstrated. Nitrous oxide accumulated as the main N-containing product of nitrate reduction. The amount of PHAs in activated sludge cultures decreased approximately 20% within 40 days of incubation. Attempts were made to establish iron- and sulfate-reducing consortia from spring water, yet it could not be demonstrated that the mixed cultures were capable of degrading PHAs. Pure cultures of iron- and sulfate-reducing bacteria could not utilize PHAs as sole carbon sources. Methanogenic environments sampled included pond sediment and rumen fluid. PHAs were fermented to methane and carbon dioxide after 10 weeks by a sediment consortium, with 43 to 57% of the substrate carbon transformed to methane. Although it could not be demonstrated that PHAs were biodegraded by a rumen fluid consortium, a facultative anaerobic bacterium, identified as aStaphylococcus sp., that could grow on PHAs was isolated from rumen fluid.     

Aging of Toughened Polylactic Acid Nanocomposites: Water Absorption,Hygrothermal Degradation and Soil Burial Analysis

The environmental aging behaviour of montmorillonite (MMT) filled polylactic acid (PLA) nanocomposites (PLA/MMT) and linear low density polyethylene (LLDPE)-toughened PLA (PLA/LLDPE ratio = 90/10) nanocomposites (PLA/LLDPE/MMT) were investigated in this study. The nanocomposites were subjected to water absorption, hygrothermal degradation and soil burial analysis. Both PLA/MMT and PLA/LLDPE/MMT nanocomposites were immersed in distilled water at three different temperatures (room temperature, 60, and 90 °C) and the weight difference before and after immersion was calculated. The kinetics of water absorption for both nanocomposites followed the Fick’s second law of diffusion, where a linear relationship exists between the initial moisture absorption at any time t and t ^1/2 (the square root of time), followed by a horizontal plateau (saturation). The equilibrium moisture content (M _m ) and diffusion coefficient (D) of PLA nanocomposites increased with the addition of MMT (2 phr) and LLDPE. However, the D values of both nanocomposites decreased by increasing MMT (4 phr). The M _m for PLA/MMT and PLA/LLDPE/MMT nanocomposites increased by increasing immersion temperature (60 °C) and prolonged immersion resulted in hygrothermal degradation of both nanocomposites. The hygrothermal degradation studies showed that PLA degrades much faster at 90 °C as compared to 60 °C in both the nanocomposites. The addition of MMT and LLDPE improved the hygrothermal stability of PLA in both nanocomposites. Soil burial test revealed deterioration of impact strength in all samples while the rate of biodegradation was retarded in the presence of MMT and LLDPE.     

Distribution of Poly(β-propiolactone) Aerobic Degrading Microorganisms in Different Environments

The distribution of degading microorganisms of high molecular weight poly(-propiolactone) (PPL), whose individual structural units are similar to those of poly(-hydroxybutyrate) (PHB) and poly(€-caprolactone) (PCL), was examined. Despite the fact that PPL is a chemosynthetic polymer, many kinds of PPL-degrading microorganisms were found to be distributed as resident populations widely in natural environments. A total of 77 strains of PPL-degrading microorganisms was isolated. From standard physiological and biochemical tests, at least 41 strains were referred to as Bacillus species. Microbial degradation of fibrous PPL proceeded rapidly in some enrichment cultures but was not as complete as that of PHB. Most of the isolated PPL-degrading microorganisms were determined to be PCL degraders and/or PHB degraders. Therefore, it can be assumed that mostly PPL is recognized by the microorganisms as PHB or another natural substrate of the same type as which PCL is regarded. Microbial degradation of PPL was confirmed by some Bacillus strains from type culture collections. The similarity of microbial degradation between PPL and PCL was found to be very close.     

Lysinibacillus sphaericus and Geobacillus sp Biodegradation of Petroleum Hydrocarbons and Biosurfactant Production

Petroleum oil is a major driver of worldwide economic activity, but it has also created contamination problems during the storage and refining process. Also, unconventional resources are natural resources, which require greater than industry‐standard levels of technology or investment to exploit. In the case of unconventional hydrocarbon resources, additional technology, energy, and capital have to be applied to extract the gas or oil. Bioremediation of petroleum spill is considered of great importance due to the contaminating effects on human health and the environment. For this reason, it is important to reduce total petroleum hydrocarbons (TPH) in contaminated soil. In addition, biosurfactant production is a desirable property of hydrocarbon‐degrading microorganisms. Seven strains belonging to Lysinibacillus sphaericus and Geobacillus sp were selected to evaluate their ability to biodegrade TPH in the presence of toxic metals, their potential to produce biosurfactants, and their ability to improve the biodegradation rate. The seven bacterial strains examined in this study were able to utilize crude petroleum‐oil hydrocarbons as the sole source of carbon and energy. In addition, their ability to degrade crude oil was not affected by the presence of toxic metals such as chromium and arsenic. At the same time, the strains were able to reduce toxic metals concentration through biosorption processes. Biosurfactant production was determined using the drop‐collapsed method for all strains, and they were characterized as both anionic and cationic biosurfactants. Biosurfactants showed an increase in biodegradation efficiency both in liquid minimal salt medium and landfarming treatments. The final results in field tests showed an efficiency of 93 percent reduction in crude oil concentration by the selected consortium compared to soil without consortium. The authors propose L. sphaericus and Geobacillus sp consortium as an optimum treatment for contaminated soils. In addition, production of biosurfactants could have an application in the extraction of crude oil from unconventional hydrocarbon resources. © 2014 Wiley Periodicals, Inc.     

Sorting efficiency and combustion properties of municipal solid waste during bio-drying

One aerobic and two combined bio-drying processes were set up to investigate the quantitative relationships of sorting efficiency and combustion properties with organics degradation and water removal during bio-drying. Results showed that the bio-drying could enhance the sorting efficiency of municipal solid waste (MSW) up to 71% from the initial of 34%. The sorting efficiency was correlated with water content negatively (correlation coefficient, r = −0.89) and organics degradation rate positively (r = 0.92). The higher heating values (HHVs) were correlated with organics degradation negatively for FP (i.e. the sum of only food and paper) (r = −0.93) but positively for the mixing waste (MW) (r = 0.90), whereas the lower heating values (LHVs) were negatively correlated with water content for both FP (r = −0.71) and MW (r = −0.96). Other combustion properties depended on organics degradation performance, except for ignition performance and combustion rate. The LHVs could be greatly enhanced by the combined process with insufficient aeration during the hydrolytic stage. Compared with FP, MW had higher LHVs and ratios of volatile matter to fixed carbon. Nevertheless, FP had higher final burnout values than MW.     

Synthesis of a block copolymer of poly(3-hydroxybutyrate) and poly(ethylene glycol) and its application to biodegradable polymer blends

A block copolymer {P[(R,S)-HB-b-EG]} of atactic poly[(R,S)-3-hydroxybutyrate] {P[(R,S)-HB]} and poly(ethylene glycol) (PEG) was prepared by the ring-opening polymerization of -butyrolactone in the presence of a macroinitiator (PEG/ZnEt₂/H₂O) which had been produced by the reaction of ,-dihydroxy PEG ( _n=3000) with ZnEt₂/H₂O (1/0.6) catalyst. The block copolymer ( _n=10,500, _w/ _n=1.2) was an A-B-A triblock copolymer comprising atactic P[(R,S)-HB] (A) and PEG (B) segments. The miscibility, physical properties, and biodegradability of binary blends of microbial poly[(R)-3-hydroxybutyrate] {P[(R)-HB]} with the block copolymer P[(R,S)-HB-b-EG] has been studied. The glass-transition temperature (T _g) data showed that the P[(R)-HB]/P[(R,S)-HB-b-EG] blend was miscible in the amorphous state. The P[(R)-HB] film became flexible and tough by means of blending with P[(R,S)-HB-b-EG] block copolymer. The enzymatic degradation of blend films was carried out at 37°C and pH 7.4 in a 0.1M phosphate solution of an extracellular PHB depolymerase fromAlcaligenes faecalis. The enzymatic degradation took place solely on the surface of the blend films.     

A Retrospective Isotopic Study of Spruce Decline in the Vosges Mountains (France)

The objective of this study was to assess the time variation of mineral and water stress levels across the life of a declining, Mg-deficient, spruce stand, in order to clarify the factors that caused the decline. Since 1985, strong soil acidification linked to a large leaching of nitrate and base cations was measured at the study site. In 1994, 5 trees were felled and tree rings were measured and analysed for Ca, Mg, K, Sr, ¹³C¹²C and ⁸⁷Sr/⁸⁶Sr isotopic ratios. Strontium pools and fluxes as well as root Sr isotope ratio in relation to depth were also measured. Wood chemical concentrations and isotope ratios were strongly related to the dominance status of each tree. On average during the study period, the ⁸⁷Sr/⁸⁶Sr ratio of spruce wood decreased. Using a mechanistic model computing long term variations of ⁸⁷Sr/⁸⁶Sr ratio in trees and soils, we reproduced the observed trend by simulating soil acidification – increasing Sr drainage from the whole profile, and particularly from the organic horizon –, and root uptake becoming more superficial with time. Between 1952 and 1976, tree ring ¹³C decreased strongly and continuously, which, in addition to other factors, might be related to an increase in water stress. Thus, a decrease in rooting depth, possibly related to soil acidification, appeared as a possible cause for the long term increase in water stress. The extreme drought event of 1976 appears to have revealed and triggered the decline.     

Iron‐mediated abiotic degradation of RDX in a contaminated aquifer

The influence of aqueous‐ and mineral‐phase iron on royal demolition explosive (RDX) destruction has been previously investigated in theoretical settings and bench‐scale tests by various practitioners. The feasible use of in situ redox manipulation to create reactive Fe(II) is contingent upon the aquifer containing enough iron oxides and iron‐bearing clay minerals for the treated zone to remain effective. The following is a summary of a bench‐scale assessment of this relationship using aquifer material from an ongoing groundwater remediation effort at the Iowa Army Ammunition Plant (IAAP). A bench‐scale study was designed to determine the relative contributions of the biotic and iron‐mediated abiotic degradation processes to the net decrease in RDX observed at the site using saturated aquifer samples collected from within the RDX plume. Sterilized samples with a sufficient stoichiometric excess of both soluble and mineral‐phase iron reduced concentrations of RDX in both the soil and water fractions to the same extent as the samples containing native biota. These results indicate that in situ, abiotic degradation of RDX is feasible in areas unsuitable to biotic degradation processes, yielding an additional alternative for in situ RDX remediation. © 2012 Wiley Periodicals, Inc.     

Enzymatic Degradation and Aminolysis of Microbial Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) Single Crystals

Solution-grown single crystals of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] were hydrolyzed by polyhydroxybutyrate (PHB) depolymerase from Ralstonia pickettii T1. Enzymatic degradation proceeded from the edges of lamellar crystals, yielding serrated contour and small crystal fragments. Gel permeation chromatography analysis revealed that the molecular weights of the crystals decreased during enzymatic degradation, suggesting that the enzymatic hydrolysis of chain-folding regions at the crystal surfaces occurred in addition to the enzymatic degradation at crystal laterals or edges. After P(3HB-co-4HB) single crystals were aminolysed in 20% aqueous methylamine solution to remove the folded-chain regions and enzymatic degradation by lipase from Rhizopus oryzae to remove 4HB components at crystal surfaces of single crystal aminolyzed, it was found that a small amount (up to ca. 2 mol%) of 4HB component can be incorporated into the P(3HB) mother crystal lattice irrespective of the 4HB content.     

1,3-Propanediol Production Potential by a Locally Isolated Strain of Klebsiella Pneumoniae in Comparison to Clostridium Beijerinckii NRRL B593 from Waste Glycerol

The fermentative production of 1,3-propanediol (1,3-PDO) by Klebsiella pneumoniae under different initial substrate concentrations (between 5 and 110 g/L) was investigated. It was found that glycerol was almost 100% utilized and 1,3-PDO production increased up to 20 g/L of influent substrate concentration, but there was a significant decrease in both glycerol consumption and 1,3-PDO production at substrate concentrations exceeding 20 g/L. Furthermore, pH control was essential, and a lack of pH control negatively effects of 1,3-PDO production. In the second part of the study, two microorganisms, namely Clostridium beijerinckii NRRL B593 and K. pneumoniae were comparatively studied in terms of their 1,3-PDO productivity under pH controlled conditions. Higher 1,3-PDO production was achieved under pH controlled fermentation conditions (pH = 7) for both microorganisms. Even though the two microorganisms had almost the same 1,3-PDO yield (0.60 mol/mol for C. beijerinckii, 0.61 mol/mol for K. pneumoniae) at the end of fermentation period, K. pneumoniae completed the 1,3-PDO production in one-third of the time (t = 8 h with a productivity of 1.34 g/L/h) than C. beijerinckii (t = 24 h). The results of this study clearly indicated that a substrate inhibition is a challenge that needs to be studied further for higher productivities.     

Bioremediation of PCP-contaminated soil: Bench to full-scale implementation

Pentachlorophenol (PCP) is a widely used wood treatment agent and pesticide that is often listed among the contaminants at hazardous waste sites. Bench-scale studies were performed to develop a microbial culture and biodegradative process that could treat PCP at higher concentrations than previously reported. Several substrate formulations and culture techniques were evaluated. Ultimately a “self-feeding” (pH auxostat) continuous culture system (pH auxostat) was used to select for biodegradative activity with PCP as the carbon and energy source. After a period of 50 days, influent PCP concentrations reached 3,500 mg/liter at a dilution rate of 0.066 H^?1. Of the total theoretical chloride that could be released from PCP, 99% was detected as free chloride in the reactor effluent. PCP analysis of the effluent verified complete degradation by the microbial consortium. The reactor was converted to a constant PCP feed. At steady state conditions, the dilution rate was 0.05 H^?1 with an influent PCP concentration of 2,560 mg/liter and a biomass yield of 018 mg (dry weight) per mg of PCP. Mineralization studies performed with the microbial consortium using [U-14C1]-PCP indicated that 36.5% of the label was released as 14C-carbon dioxide.     

Influence of Processing Additives on the Degradation of Melt-Pressed Films of Poly(ε-Caprolactone) and Poly(Lactic Acid)

Melt-pressed films of polycaprolactone (PCL) and poly(lactic acid) (PLA) with processing additives, CaCO₃, SiO₂, and erucamide, were subjected to pure fungal cultures Aspergillus fumigatus and Penicillium simplicissimum and to composting. The PCL films showed a rapid weight loss with a minor reduction in the molecular weight after 45 days in A. fumigatus. The addition of SiO₂ to PCL increased the rate of (bio)erosion in A. fumigatus and in compost. The use of a slip additive, erucamide, was shown to modify the properties of the film surface without decreasing the rate of bio(erosion). Both the rate of weight loss and the rate of molecular weight reduction of PCL increased with decreasing film thickness. The addition of CaCO₃ to PLA significantly reduced the thermal degradation during processing, but it also reduced the rate of the subsequent (bio)degradation in the pure fungal cultures. PLA without additives and PLA containing SiO₂ exhibited the fastest (bio)degradation, followed by PLA with CaCO₃. The degradation of the PLA films was initially governed by chemical hydrolysis, followed by an acceleration of the weight change and of the molecular weight reduction. PLA film subjected to composting exhibits a rapid decrease in molecular weight, which then remains unchanged during the measurement period, probably because of crystallization.     

Improvement of digestibility of sunflower and corn residues by some saprophytic fungi

The in vitro degradation of fiber from two agricultural residues (Helianthus annuus and Zea mays) was studied using four saprophytic fungi. The changes in cellulolytic enzyme and phosphatase activities, the C/N ratio, the dry weight, the crude fiber (CF) content, and the protein and fiber digestibility coefficients were investigated in solid-state culture during a 45-day period of biodegradation. The FPase activity of Phanerochaete chrysosporium and the endoglucanase activities of P. chrysosporium and Trichoderma reesei compared to those of the other fungi were significantly (P < 0.05) high on both crop resides. Both acid and alkaline phosphatases were produced in greater amounts by P. chrysosporium than by the other fungi. The organic carbon contents of both residues were reduced more by T. reesei than by the other fungi. The fiber digestibility coefficient of untreated corn residue was higher than that of sunflower residue, but after treatment with fungi, the sunflower fiber digestibility increased more than that of corn did. Although the CF contents of both residues were decreased more by P. chrysosporium than by T. reesei, the fiber digestibility coefficients of both residues were increased more by T. reesei than by P. chrysosporium. The treatment of both crop residues increased their protein digestibility coefficients significantly compared to the control. The protein digestibility coefficients of both residues were increased more by T. reesei and P. chrysosporium than by the other fungi. In all treatments, the protein digestibility coefficient of sunflower residue was higher than that of corn residue.     

Synthesis of copolyesters containing poly(ethylene terephthalate) and poly(ε-caprolactone) units and their susceptibility toPseudomonas sp. lipase

Copolyesters containing poly(ethylene terephthalate) (PET) and poly(-caprolactone) (PCL) were synthesized from PET and PCL homopolymers by transesterification reaction at 270°C in the presence of catalyst. The copolyesters were characterized by¹³C-NMR and differential scanning calorimetry (DSC). The degradation behavior of PCL byPseudomonas sp. lipase in buffer solution (pH 7) and tetrahydrofuran (THF) was investigated by gel permeation chromatography (GPC) and¹H-NMR. From these experiments, it was found thatPseudomonas sp. lipase acted endoenzymatically on PCL. Using this lipase, degradation tests for PET/PCL copolyesters whose PCL content was below 50% by weight were also performed in buffer solution (pH 7). However, evenPseudomonas sp. lipase with high degradation activity on PCL did not easily degrade the PCL unit in PET/PCL copolyesters.