The biodegradable biopolymer polylactic acid (PLA) has been used in the recent past in single-use packaging as a suitable replacement for non-biodegradable fossil fuel-based plastics, such as polyethylene terephthalate (PET). Under FDA and EU regulations, lactic acid (LA), the building block of PLA, is considered safe to use as a food contact material. The mechanical, thermal, and barrier properties of PLA are, however, major challenges for this material. PLA is a brittle material with a Young’s modulus of 2996–3750 MPa and an elongation at break of 1.3–7%. PLA has a glass transition temperature (Tg) of 60 °C, exhibiting structural distortion at this temperature. The water permeability of PLA can lead to hydrolytic degradation of the material. These properties can be improved with biopolymer blending and composites. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), for instance, increases the thermal stability of PLA while decreasing the water permeability by up to 59%. Polypropylene (PP) is one of the most common plastics in reusable food containers. This study will compare PLA-based blends and composites to the currently used PP as a sustainable alternative to fossil fuel-based plastics. The end-of-life options for PLA-based food containers are considered, as is the commercial cost of replacing PP with PLA.

C⁴‐substituted fluoroprolines (4R)‐fluoroproline ((4R)‐Flp) and (4S)‐fluoroproline ((4S)‐Flp) have been used in protein engineering to enhance the thermodynamic stability of peptides and proteins. The electron‐withdrawing effect of fluorine can bias the pucker of the pyrrolidine ring, influence the conformational preference of the preceding peptide bond, and can accelerate the cis/trans prolyl peptide bond isomerisation by diminishing its double bond character. The role of 4,4‐difluoroproline (Dfp) in the acceleration of the refolding rate of globular proteins bearing a proline (Pro) residue in the cis conformation in the native state remains elusive. Moreover, the impact of Dfp on the thermodynamic stability and bioactivity of globular proteins has been seldom described. In this study, we show that the incorporation of Dfp caused a redox state dependent and position dependent destabilisation of the thioredoxin (Trx) fold, while the catalytic activities of the modified proteins remained unchanged. The Pro to Dfp substitution at the conserved cisPro76 in the thioredoxin variant Trx1P did not elicited acceleration of the rate‐limiting trans‐to‐cis isomerization of the Ile75‐Pro76 peptide bond. Our results show that pucker preferences in the context of a tertiary structure could play a major role in protein folding, thus overtaking the rules determined for cis/trans isomerisation barriers determined in model peptides.

Single-use plastics (SUPs) in life science laboratories account for approximately 5.5 million tonnes of waste per year globally. Of SUPs used in life science laboratories, Petri dishes, centrifuge tubes, and inoculation loops are some of the most common. In order to reduce the reliance on petrochemical-based SUPs in the life science research laboratory and minimize the negative environmental impacts associated with SUPs, this research investigates the applicability of polylactic acid (PLA) in single-use labware as a replacement for petrochemical-based plastics. PLA is one of the most well-studied biodegradable plastics that can be produced from sustainable resources. Commercially available PLA was used to 3D print a select range of labware to test the suitability of PLA-based material for routine microbiology work. An injection moulded PLA-based Petri dish was also designed and produced, for increased optical clarity. The biocompatibility was tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus epidermidis) strains of bacteria. The PLA-based labware did not negatively impact the cell growth, viability, and metabolic activity of the bacterial cultures. The injection moulded PLA Petri dish showed a reduced colony forming unit count for the Gram-negative E. coli strain compared to the polystyrene Petri dish, ∼1.5 × 10⁹ CFU/mL and ∼3.0 × 10⁹ CFU/mL respectively, during late-exponential growth. The colony counts were, however, in the same order of magnitude. This observed difference may be due to the internal environment inside the Petri dish, hence the internal O₂ concentration, humidity, and temperature during bacterial growth were investigated. This work demonstrates, for the first time, a full successful workflow of bacterial growth using a sustainable bioplastic, providing a pathway to reducing the environmental impacts of SUPs in life science laboratories.