Polyhydroxyalkanoates (PHA) production from brewer's spent grain

Overview

This research program addresses the high cost barriers in current biopolymer production by developing non-sterile, mixed microbial fermentation processes to convert brewer's spent grain into polyhydroxyalkanoates (PHA). Brewer's spent grain is a high-volume, low-cost waste stream from brewing operations, making it an attractive feedstock for sustainable biopolymer manufacturing. The work builds on prior demonstration of compostable cellulose-based multilayer materials using agricultural waste, which achieved a 19% reduction in carbon footprint compared to PET and exhibited strong barrier properties suitable for packaging applications.

The solution targets food-contact packaging and other applications where compostable, high-performance biocomposites are needed. By integrating locally sourced waste feedstocks with simplified fermentation processes, the approach aims to achieve cost parity with conventional plastics while delivering environmental benefits.

Technical specifications

Feedstock and process innovation:

• Utilizes brewer's spent grain, a locally generated waste stream with high availability and low cost
• Mixed microbial fermentation eliminates the need for sterile processing, reducing capital and operating costs
• Three-stage experimental approach to select microbes capable of accumulating PHA at high rates

Prior material achievements:

• Cellulose isolated from wheat straw melt-extruded with commercial PHA
• Plant-based protein coating applied to enhance barrier performance
• Oxygen transmission rate (OTR) of 12–20 cm³·100µm·m⁻²·d⁻¹·bar⁻¹
• Water vapour transmission rate (WVTR) of 30 g·100µm·m⁻²·d⁻¹
• Multilayer composition: 69% PHA, 29% cellulose, 2% coating
• Cradle-to-grave LCA showing 19% carbon footprint reduction versus PET

Downstream processing and validation:

• Stabilization of PHA-rich biomass followed by purification to obtain pure PHA
• Thermal and chemical characterization to confirm industrial-grade quality
• Migration and organoleptic testing to verify food-contact regulatory compliance
• End-of-life assessment and energy/carbon footprint quantification
• Manufacturing using only authorized starting substances and additives for food-contact materials

Technology readiness level

The underlying cellulose recovery and biocomposite processing capabilities have been validated through feedstock availability assessments, methodology development for biopolymer building block recovery, and processing on industrial production infrastructure into multilayer sheets and thermoformed products. The PHA production from spent grain is currently at an optimization stage, with planned three-stage microbial selection trials, downstream process development, and comprehensive characterization and regulatory testing to demonstrate consistent industrial quality and end-of-life performance.