Dear Colleagues,

Common plastics of fossil fuel origin are persistent in nature, representing a serious and growing environmental problem. These plastics can be replaced in diverse applications by bio-based polymers like polyhydroxyalkanoates (PHAs). PHAs are biodegradable and can be produced from numerous wastes and by-products by more than 300 genera of prokaryotes.

PHAs act as internal carbon and energy reserves in bacteria, allowing for survival in environments that experience unbalanced nutritional conditions. One example of these conditions is the limitation of nutrients required for growth, such as oxygen or nitrogen, when carbon is present in excess. Another example is the alternation of periods of lack and availability of carbon sources. Also, due to the high diversity of monomers and the possibility to combine different monomers into the final polymer, a wide range of properties can be obtained for this class of polymers, from thermoplastics to elastomers, with a wide range of applications. Although PHAs can replace many types of petrol-derived plastics, their production price is not yet commercially attractive. Researchers in this field still need to tackle several challenges in order to make the industrial production of PHAs competitive with the well-established industry of conventional plastics. These challenges include high cell density processes, the use of cheap and fast metabolized substrates, fast-growing strains, low sterility processes, high cell contents, and easier downstream processing.

This Special Issue intends to cover the latest developments in this field including all types of producing microorganisms—pure, recombinant, and mixed microbial cultures. Topics will include the use of new raw materials as the substrate; the selection, enrichment, screening, and isolation of novel producers; reactor operation; metabolic engineering for production improvement; downstream processing; process scale-up; polymer characterization; and polymer applications/blends.

Prof. Luísa Seuanes Serafim
Dr. Paulo Costa Lemos
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• Biopolymers
• Polyhydroxyalkanoates
• Bacterial production
• Mixed microbial cultures
• Recombinant organisms
• Cheap raw materials
• Downstream