Brewers' Spent Grain-Derived Arabinoxylan as a Sustainable Filler for Enhanced PHBV Biocomposites

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a highly promising biodegradable and bio-based thermoplastic recognized for its environmental benefits and potential versatility. However, its industrial adoption has been limited due to its inherent brittleness and suboptimal processability. Despite these challenges, PHBV's performance can be tailored for a wide range of applications through strategic modifications, particularly by blending it with other biodegradable polymers or reinforcing it with natural fibers and bio-based fillers. This study explores the potential of brewers' spent grain (BSG) as a sustainable source for the development of PHBV biocomposites. The biocomposites were synthesized by incorporating arabinoxylan-bound benzoate, which can be derived from BSG, as a sustainable filler at concentrations of 4% and 10% w/w. The resulting materials were characterized using tensile testing, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The findings demonstrate that the incorporation of functionalized arabinoxylan significantly enhances the mechanical properties of PHBV, preserves its thermal stability, and increases its crystallinity (from 59.9% to 67.6%), highlighting a positive impact on both material performance and processing characteristics.