[P007] Poster

12:10 PM - 1:00 PM JST(3:10 AM - 4:00 AM UTC)

[P04-561] Design of Marine-Degradable Plastics Based on Silk-Derived Proteins

○Yuri Matsumoto¹, Shota Akioka¹, Keiichi Noguchi¹, Yasumoto Nakazawa¹ (1. Biotechnology and Life Science, Graduate School of Engineering, Tokyo University of Agriculture and Technology (Japan))

Keywords:

Bioplastic,Silk fibroin,Polymer blends,Miscibility,Biodegradability

Bioplastics have attracted increasing attention as alternatives to petroleum-derived plastics, which contribute significantly to environmental pollution. However, achieving both high mechanical strength comparable to conventional plastics and sufficient biodegradability remains a major challenge. In particular, the development of materials that can degrade effectively in marine environments is still limited. As a result, biodegradable bioplastics account for less than 0.5 % of global plastic production, highlighting the need for new material strategies (European Bioplastics, Bioplastics market data 2018).In this study, we focused on silk fibroin (SF), the primary structural protein of silk. As an insect-derived biomass, SF is currently being explored for potential applications in the environmental sector. Furthermore, since it is known that a significant amount of waste fiber is generated during the processing of cocoons into silk thread (Gaviria et al., 2023), we proposed the development of bioplastics as a strategy for utilization of this unused resource. SF exhibits high mechanical strength and moderate biodegradability due to its crystalline structure formed by repetitive G–X sequences. To enhance its biodegradability, we explored blending SF with polysaccharides, which are inherently more biodegradable but mechanically weaker. However, such polymer blends often suffer from poor miscibility, resulting in compromised material performance.To address this issue, we introduced a peptide modification strategy based on the (GA) repeat motif found in SF to enhance interfacial interactions and improve compatibility between components. Pectin, a polysaccharide with abundant functional groups suitable for chemical modification, was selected as the blending partner. The effects of peptide modification and improved miscibility on material properties and biodegradability were investigated.Composite materials were prepared by freeze-drying equal-weight aqueous solutions of SF and pectin, followed by hot pressing at 150°C and 62.4 MPa to obtain resin samples (SP). Peptide-modified pectin bearing (GAGAGA) sequences via the EDC/NHS method was used to prepare modified composites (SP-A). Pure SF and pectin resins were prepared as controls. Thermal properties were evaluated by differential scanning calorimetry (DSC), and biodegradability was assessed using biological oxygen demand (BOD) measurements.DSC results showed that the increase in glass transition temperature was suppressed in SP-A compared to SP, indicating improved miscibility. Additionally, the crystallization relaxation peak was split into two upon peptide modification, suggesting the formation of crystalline domains with different stabilities. However, SP-A exhibited a lower biodegradation rate. These findings suggest that biodegradability in this system is governed more by phase structure than by molecular structure. Further characterization and discussion of the relationship between miscibility and biodegradability will be presented, highlighting the potential of this material as a novel bioplastic.This study was supported by JST COI-NEXT Program Grant Number JPMJPF2104, JSPS KAKENHI (23K13573), and by the Research and Implementation Promotion Program through Open Innovation Grants (JPJ011937) from the Bio-oriented Technology Research Advancement Institution (BRAIN).