Influence of substrate crystallinity and glass transition temperature on enzymatic degradation of polyethylene terephthalate (PET)

Standardized method for controlled modification of poly (ethylene terephthalate) (PET) crystallinity for assaying PET degrading enzymes

“…Although PET is a synthetic polymer, recent data have shown that certain esterolytic enzymes (EC 3.1.1,x), including the PET hydrolase from the bacterium Ideonella sakaineses 201-F6, originally specified as a PETase (or IsPETase) [8] , now classified as EC 3.1.1.101, are capable of catalyzing hydrolysis of the ester bonds within PET. The activity of these enzymes are, however, limited on PET samples with a high X C [9] , [10] , [11] , [12] . X C of PET in water bottles ranges from 21–31% [13] making the significance of X C on PET degrading enzyme activity of critical importance in biobased industrial PET recycling.…”

“…Here we present the practical details and the theory behind an experimental methodology that we have developed for preparing PET samples of different degrees of crystallinity, X C , to allow systematic evaluation of the efficiency of PET degrading enzymes in response to the X C of PET [11] . We introduce annealing involving controlled heating and isothermal cold crystallization to control the X C of standardized PET sheets ( Fig.…”

“…A temperature range from 20°C to 270°C is sufficient to determine the thermal features required to estimate X C and X MAF of PET samples. A constant heating rate of 10°C min −1 is recommended, as some thermal features are dependent on the heating rate [9 , 11 , 16] . The X C of a PET sample, measured by DSC, is then calculated according to Eq.…”

“…Where ∆C P(m) is the change in heat capacity of the sample at T g and ∆C P(a) is the change in heat capacity at T g of a completely amorphous sample. By extrapolation from a linear regression curve of measured ∆C P(m) values and X C of PET disk samples we have previously estimated ∆C P(a) of an amorphous PET disk sample to be approximately 0.47 J g −1 K −1 [11] .…”

“…LCC ICCG was expressed recombinantly in E. coli Shuffle T7 and purified as described in [11] (Expression also works in E. coli BL21 (DE3) cells).…”