• Energy Research

Bio-degradation assays were performed for bio-based polymers under environmental conditions with controlled temperature and pH using pH Stat titration. Suspensions of PLA and PBS microparticles, produced by e.g. cryo-milling, were incubated with proteolytic and lipolytic enzymes. Rates of hydrolysis, as determined by counter-titration with a diluted base (NaOH), was recorded for two hours. The thermal profile of PLA hydrolysis by protease was investigated. All measurements were conducted under controlled laboratory conditions. The columns headings are abbreviated and mean the following. Min: Duration of the titration in minutes; ml: Volume of added NaOH. Unless otherwise specified, c (NaOH) = 10 mM; pH: pH value of the suspension, set to 8.2; °C: Temperature of the suspension.

We present in depth data of the sea urchin population in the Arctic Porsangerfjord. Sea urchins were collected by hand from randomly chosen square meters of two present habitats: a sea urchin barren, characterized by stony ground without major algae growth, and the neighbouring kelp forest with a healthy macroalgae community. Both habitats are located near the shoreline of a bay in the Porsangerfjord, called the Holmfjord, and sampling took place in less than 1 m depth at low tide. Sampling was conducted in two consecutive years, summer 2022 and summer 2023. Data collected from the sea urchins includes the test-diameter, freshmass, species and morphotype.

Bio-based polymers have been suggested as one possible opportunity to counteract the progressive accumulation of microplastics in the environments. The gradual substitution of conventional plastics by bio-based polymers bears a variety of novel materials. The application of bioplastics is determined by their stability and bio-degradability, respectively. With the increasing implementation of bio-based plastics, there is also a demand for rapid and non-elaborate methods to determine their bio-degradability. Here, we propose an improved pH Stat titration assay optimized for bio-based polymers under environmental conditions and controlled temperature. Exemplarily, suspensions of poly(lactic acid) (PLA) and poly(butylene succinate) (PBS) microparticles were incubated with proteolytic and lipolytic enzymes. The rate of hydrolysis, as determined by counter-titration with a diluted base (NaOH), was recorded for two hours. PLA was hydrolyzed by proteolytic enzymes but not by lipase. PBS, in contrast, showed higher hydrolysis rates with lipase than with proteases. The thermal profile of PLA hydrolysis by protease showed an exponential increase from 4 to 30 °C with a temperature quotient Q10 of 5.6. The activation energy was 110 kJ·mol−1. pH-Stat titration proved to be a rapid, sensitive, and reliable procedure supplementing established methods of determining the bio-degradability of polymers under environmental conditions.