The Current State of Research on PET Hydrolyzing Enzymes Available for Biorecycling
Round 1
Reviewer 1 Report
The author in this short paper describes the current advancements in PET biorecycling, focusing on the utilization of thermophilic and mesophilic hydrolases for this purpose. Τhe author also clearly states, in his respect, the superiority of the thermophile cutinases for the hydrolysis of PET in terms of product yields based on the research works he is citing while he also presents perspectives pertaining to translation to practical application in the industry. Furthermore, the author emphasizes the need to separate the enzymes with the potential to modify than those that degrade/hydrolyze the target material.
Overall, I believe the manuscript is well written and provides the current state of the art pertaining to PET biocatalysis, while it points out that IsPETase, which has indeed attracted so much attention for its potential to be used in PET degradation cycle, it seems to be inferior to thermophilic hydrolases and there is much room for improvement, while researchers need to evaluate their findings and others and focus their efforts on essential research that will bring us closer to alleviating one of the worst environmental problems of our time, polymer waste accumulation in our ecosystem.
I have no comments for this short review/opinion just this one:
At some point in the maintext it is mentioned that:
“It is questionable whether mesophilic enzymes or their mesophilic microbial hosts contribute significantly to the hydrolysis of PET in the ecosystem, because the over-all temperatures in both the marine and terrestrial environments are lower than 30oC. We should not expect too much hydrolysis of PET by these PET hydrolase homologs, as the increase in PET waste far surpasses any biodegradation that may occur in the ecosystem.”
It is a fact that mesophilic and thermophilic enzymes or hosts do not contribute significantly to enzymatic degradation of PET in the ecosystem, considering the huge amounts of waste that have caused the plastics pollution. Temperatures at 30oC or 60-70oC are both not feasible in the marine and terrestrial environments as the author mentions. The scope of our research is the utilization of these enzymes to perform polymer hydrolysis under controlled conditions on accumulated plastic waste material for optimum efficiency and hydrolysis yields.
Author Response
Thanks for your positive response.
I have checked spells and styles (especially in references).
According to your comments, I have revised. I hope that this would be satisfactory.
Reviewer 2 Report
Addressing a serious global problem associated with plastic pollution this paper gives an excellent coverage on the current intense research on the two classes of PET hydrolyzing enzimes. The content is composed on the basis of a wide-range yet relevant selection of high-standard literature sources with special focus on critical comparative evaluation of the state-of-the art of enzymatic recycling. In its present form this review merits publication in Catalysts.
Author Response
Many thanks for your positive comments. I hope that this paper would be helpful to related researchers.
