Nanomaterial scaffolds for enzymatic polymer degradation: a tool to advance current biodegradation assessments of polymers in liquid formulation

Abstract

Polymers are used as an integral component in a wide range of liquid formulation products to improve formulation integrity and product performance. Due to environmental and regulatory pressures, it is necessary for the industry to shift away from petrochemically derived polymers to more sustainable and biodegradable products. However, current methods to analyse the biodegradation of polymers are time consuming and adapted to small molecules which is stifling innovation in this area. There is a requirement to re-envisage how the industry conducts biodegradability testing for polymers in liquid formulation (PLFs) from high-throughput screening methods at the preliminary stages of development to predictive modelling. Advancements in the use of nanomaterials as enzyme immobilisation scaffolds for polymer degradation could evolve how biodegradability testing is thought about and drive the PLF industry into a more sustainable future. This review highlights the current trends in the use of nanomaterials as enzyme immobilisation platforms and how this technology has been applied to the degradation of biodegradable PLFs.

Keywords: Biodegradation; Enzyme Immobilisation; Flow Chemistry; Nanomaterials; Polymer Degradation.

Fig. 1

Current OECD standard testing guidelines for the biodegradation of polymeric substances. Guidelines for OECD 301 C (modified Sturm test measuring CO₂ evolution) and 301 F (manometric respirometry test measuring O₂ consumption) are the most widely used industry for polymers over a minimum of 28 days and a maximum of 2 years. Biodegradability tests (OECD 301) are prepared in aqueous media inoculated with an activated wastewater treatment culture and analysed at periodic time points to assess ready and inherent biodegradability

Fig. 2

Chemical structures of the polysaccharides; A cellulose, chitin, and chitosan, B amylose and amylopectin, C Xanthan gum, and D Guar gum

Fig. 3

Representative structures of the different nanomaterials employed for enzyme immobilisation. a 0-D nanomaterials e.g. nanoparticles, b 1-D nanomaterials e.g. nanorods and nanowires, c 2-D nanomaterials e.g. nanosheets, d 3-D nanomaterials e.g. hollow mesoporous silica nanoparticles

Fig. 4

Proposed method to conduct enzymatic degradation studies of polymers, i) identify key enzyme homologs of environmental samples and isolate for in vitro testing, ii) immobilise isolated enzyme on nanoparticle/nanomaterial scaffold to improve reusability and performance, iii) conduct in vitro experiments either in batch or continuous flow allowing superior biodegradation data analysis to current methods