Performing Department
(N/A)
Non Technical Summary
Plastics have long been a mainstay in packaging applications, with approximately half of all fossil fuel-based plastics going toward food packaging. Unsurprisingly, the pervasive use of single-use plastics for food packaging has come under intense scrutiny as concerns mount over plastics' longevity and their impacts on our bodies and the broader environment. Replacement of plastics with paper-based packaging comes with its own issues, a notable example being the growing body of evidence that PFAS-coated paper products lead to health risks. While there are a few bioplastics companies that have been created in recent years, adoption into a global commodity market is stymied by two fundamental technology issues: cost and performance. RETRN Bio is enabling next-generation sustainable fiber-based packaging that can meet this challenge through development of high-performing fully biodegradable barrier coatings upcycled from agro-industrial waste residues. The RETRN process 1) sustainably sources agro-industrial and other lignocellulosic waste streams as primary feedstocks and 2) uses a novel, patent-pending technology for low-cost production of unique polymers with desirable properties, resulting in 3) a broad material platform of fully biodegradable, natural polymers that can provide the needed barrier properties to fiber-based packaging of food products (e.g. paper cups, food containers, etc.).To achieve our goals, we will use genetic engineering to improve our biological production platform to better utilize waste forest product residues. With these new production methods, we will generate a variety of different bioplastic formulations and test them against industry specifications for thermal and mechanical properties, barrier properties, and key recyclability criteria. Working with the Forest Products Lab, we will analyze strategic forest residues and raw materials to ensure their compatibility with our production platform as a feedstock. Finally, we will develop environmentally friendly aqueous coating methods to apply these bioplastics to paper packaging materials and determine their specific barrier properties (e.g. moisture vapor resistance, resistance to water/oil/grease penetration, and oxygen transmission). The project results will then be used to generate prototype materials for evaluation of product functionality by industry partners, the confirmation of which will de-risk the technology for further investment and evaluation of manufacturability in scale-up projects. Ultimately, successful commercialization of this technology would place the U.S. as a key producer of biodegradable biopolymers, will aid the transition away from the conventional plastics economy, and encourage the diversion of more food waste from landfills to composting systems.
Animal Health Component
50%
Research Effort Categories
Basic
25%
Applied
50%
Developmental
25%
Goals / Objectives
Plastics have long been a mainstay in packaging applications, with approximately half of all fossil fuel-based plastics going toward food packaging.Unsurprisingly, the pervasive use of single-use plastics for food packaging has come under intense scrutiny as concerns mount over plastics' longevity and their impacts on our bodies and the broader environment.While there are a few bioplastics companies that have been created in recent years, adoption into a global commodity market is stymied by two fundamental technology issues: cost and performance.Reliance on farmed food crops, such as corn or soybean oil, adversely affects sustainability and increases biopolymer production costs. At the same time, currently commercialized waste-based processes result in materials with a very limited degree of tunability and therefore a narrow range of applications fit for commercial application.Food packaging companies are seeking barrier coating solutions offering similar mechanical properties to PFAS, but without the toxic effects on human and environmental health. Additionally, to meet market demands for sustainability these new coating solutions must also be marine biodegradable and home compostable (unlike the majority of market-available biopolymers).As described earlier, current biopolymers suffer from critical limitations in availability, cost, sustainability, and functionality.Customers throughout the packaging value chain have indicated that large-scale adoption of biodegradable bioplastics is contingent on the resolution of these problems. While the persistence of these extensive challenges speaks to their technical difficulty, it also presents an opportunity for market disruption by novel technologies capable of bridging the gaps between sustainability and commercial feasibility.Addressing these needs, our major goal at Retrn is to developa novel technology for the conversion of lignocellulosic waste into high-performance, fully biodegradable natural polymers, designedfor use as barrier coatings in single-use food packaging as a beachhead market. Sourced from agricultural waste, our biopolymers will be tailorable to various applications in single-use packaging, thus improving the sustainability and safety of consumer products, from food wrappings to skincare.Through thisproject, we seek to develop and validate the efficacy of our platform to deliver high-value, well-controlled biopolymers using agro-industrial waste products, capable of meeting the coating barrier properties (i.e., MVTR, oil-, grease-resistance) needed in the single-use food packaging space.Successful completion of the proposed Phase I work will establish the suitability of our approach to create high-value PHAs from a typical, easily available lignocellulosic waste stream, while also establishing industry-compatible methods for the target application in barrier-coatings for fully biodegradable, fiber-based packaging. Technical de-risking in Phase I will lay the groundwork for Phase II expansion of the platform to deliver properties needed in additional potential markets (e.g., skincare packaging) and process scaleup required for pilot demonstration with industry partners.TECHNICAL OBJECTIVESThis Phase I project seeks to develop and validate the technology as a commercially viable platform delivering biodegradable coating solutions for the paper packaging industry.Objective 1. Engineer a new biological production method to improve utilization of forest residue and agro-waste resources(Retrn).While preliminary data have shown our current production strain is able to create tunable copolymers in appreciable yields from simple ideal substrates (lab conditions),tunability and yields are lost with growth on more complexsubstrates representative of forest residue materials. To improve uptake and utilization of complex substrates for tunable PHA copolymer synthesis,we will engineer mutant strains with an altered metabolism.Production based on modelfeedstocks, in direct comparison to lignocellulosic hydrolysates provided by USDA Forests Products Lab (FPL) under Objective 3, will be evaluated for PHA productivity in the new mutant strains alongside our current production strain.Objective 2. Develop a synthesis method for PHA copolymer products demonstrating commercializable thermal and mechanical properties (Retrn). One of the most valuable contributions of Retrn's patented technology is its ability to controllably produce a wide range of specific PHA copolymers. Since the brittleness and processability of currently available PHAs has limited their commercial viability as paperboard barrier coatings, we will focus primarily on manipulating polymer synthesis to address these challenges. This will be done by creating PHA copolymers with compositions (side-chain lengths, monomer inclusions) targeted towards published values which have demonstrated the melting temperatures, glass transition temperatures, tensile strengths, and % elongations required for manufacturing processes and final applications. Screened PHA products that meet specifications will be then used for further evaluation in Objective 4.Objective 3. Produce and characterize hydrolysates from softwood kraft pulp and recycled paper mill rejects (USDA FPL). To ensure compatibility of the developed biotechnology with strategic lignocellulosic raw materials, we will produce softwood kraft pulp (unbleached kraft pulp, UBK) with a kappa number resembling that of recycled paper mill rejects. UBK will be screened for fibers with the same dimensions as recycled paper mill rejects. Refined UBK and recycled paper mill rejects will be enzymatically hydrolyzed to create liquid hydrolysates, which will then be analyzed for sugar and potential inhibitor (acetate, furan) composition. The hydrolysates produced in duplicates will be supplied to the RetrnTeam for Objective 1.Objective 4. Formulate PHA emulsions and evaluate their film formation and barrier properties on paperboard (SUNY ESF).To ensure ease of adoption, the PHAs will need to be offered in emulsion form to be compatible with liquid coating processes used in the packaging industry. We will investigate a variety of industrial water-based emulsion forming techniques (e.g., sonication, high shear homogenization) and formulations containing ingredients such as surfactants, plasticizing agents, and biocides. Dispersions will be applied via rod by automatic coater to paperboard grade paper, and will be evaluated for film formation under different drying conditions. The coated paperboard will be tested for barrier properties including resistance to oil, water, and grease, as well as water vapor and oxygen transmission rate (OTR). We will also conduct an initial investigation on the recyclability of the coated paper. commercial viability of our platform to transform lignocellulosic waste feedstocks into PHAs with desirable and tunable mechanical properties, in a form amenable for commercial adoption for paper-based barrier coatings.
Project Methods
Objective 1. Engineer a new biological production method to improve utilization of forest residue and agro-waste resources.To improve uptake and utilization of complex substrates for tunable PHA copolymer synthesis, we will engineer mutant strains with modificationsto their metabolism.Successful mutants will be validated by the gain and loss of antibiotic resistance, colony PCR, and by Sanger sequencing of the mutated loci. The kinetics of substrateconsumption will be analyzed for the mutant strains developed to determine the optimal strain for consumption of each substrate. Initial tests will be performed using lab-grade materials at defined concentrations inbatch fermentations.Cell-free supernatants will be analyzed using a combination of liquid and gas chromatogaphies to measuresubstrate and product concentrations. Later tests will be performed with hydrolysates developed in Objective 3, and analyzed in the same manner. The data gathered from these experiments will be analyzed to determine the specific growth rate (µ) and yield coefficient with eachfeedstock, the rate of substrate depletion, and the PHA titer and composition. Significant differences between strains will be determined using a one-way analysis of variance (ANOVA) with a post-hoc Tukey's test. A p < 0.05 will be considered significant. Using this data, we will identify a mutation or set of mutations with the ability to optimally utilize target substratesto generate our target PHA copolymers. Evaluationmetrics:Identify the best performing production strain based on specific growth rate (µ), yield coefficient (g biomass/ g substrate), PHA production (g PHA / g biomass), and MCL copolymer yield (g MCL copolymer / g substrate).Objective 2: Develop a synthesis method for PHA copolymer products demonstrating commercializable thermal and mechanical properties.Initially, we will use laboratory grade carbon sources to biosynthesize our PHA copolymers as previously reported by the team. PHA yield and monomer composition will be analyzed directly from dried cell biomass using GC-FID. We will also use 13C NMR spectroscopy to determine how fermentation conditionsinfluences the polymer structure (i.e. blocky vs random copolymers). Once we have generated a range of random copolymers containing PHHx or PHO comonomers between 10-50 mol%, they will be extracted and purified by Soxhlet extraction and non-solvent precipitation. The PHAs developed will be analyzed for key thermal and mechanical properties. Differential scanning calorimetry (DSC) will be used to determine the glass transition temperature and melting temperature. Dynamic mechanical analysis (DMA) will be used to determine key performance characteristics such as Young's modulus and ultimate tensile strength. Data gathered will allow us to identify an ideal copolymer or set of copolymers that meet our target specifications for thermal and mechanical properties, which will inform our production experiments using hydrolysates as feedstocks in Objective 1.EvaluationMetrics:Demonstrate production of PHA products with desirable properties in the ranges of 0.5-2 GPa Young's Modulus; 15-600% elongation at break; <0 °C glass transition temperature; 110-130°C melting temperature.Objective 3: Produce and characterize hydrolysates from softwood kraft pulp rejects and recycled paper mill rejects. The USDA FPL team will conduct standard kraft pulping experimentswithtypical softwood species used in the production of unbleached pulp; Lodgepole pineto produce pulp, UBK with the lignin content of ~8%, close to the lignin content in recycled papermill reject fibers, RPR fibers supplied as never dried by the partner company WestRock. The UBK fibers will be refined to reach freeness close to the CSF of RPR fibers. Enzymatic hydrolysis (EH) will be conducted using a mixture of cellulose and hemicellulose hydrolyzing enzymes which act synergistically to release monomeric sugars. EH will be performed at standard conditions at different enzyme loadings to select a minimal enzyme dosage that achieves a high yield of sugars. After the enzyme dosage is selected, EH will be performed to produce ~300 mLhydrolysates at 30 g sugars/L from UBK and RPR fibers to send to the RetrnTeam for polymer synthesis. The chemical composition of UBK and RPR fibers will be determined via conventional two-step acid hydrolysis, followed by the analysis of the hydrolysate for monosaccharides using HPAEC with pulsed amperometric detection (PAD). The results will include the lignin content, ash content, and the contents of glucose, xylose, mannose, galactose, arabinose, and rhamnose in UBK and RPR fibers. Hydrolysates of these two types of fibers will be analyzed for monosaccharides using HPAEC-PAD. The concentration of acetic acid and the total concentration of furfural (F) and hydroxymethylfurfural (HMF) as fermentation inhibitors will be determined using1H NMR spectral analysis. The results will include the concentrations of monosaccharides,acetic acid, and the total concentration of F and HMF in UBK and RPR enzymatic hydrolysates. The yields of sugars produced from UBK and RPR fibers via enzymatic hydrolysis will be calculated.EvaluationMetrics: Produce softwood Kraft pulp and recycled paper mill rejects hydrolysates with total sugar concentrations between 30 and 90 g/L, glucose and xylose combined fraction >95%, glucose:xylose ratios between 8:1 and 11:1.Objective 4: Formulate PHA emulsions and evaluate their film formation and barrier properties on paperboard. We will develop methods to emulsify PHA in an aqueous medium, a form compatible with coating processes used in the packaging industry. A combination of surfactants, rheology modifiers, wetting agents, dispersing agents, coalescing agents, nucleating agents, cross linking agents, temperature control, and mechanical dispersion methods (e.g., high shear homogenization) will be tried on the preparation of PHA aqueous emulsion. All emulsification agents will be chosen based on FDA approval for food contact. The rheological properties of the prepared emulsions will be determined, andemulsions will be cast on a glass slide to evaluate the film-forming capability using optical microscopy. The prepared PHA emulsion will be applied on the surface of uncoated and coated paperboard by automatic meter bar coater. Different rod coaters will be used to apply different coating weights, and the number of coating layers and application to top, bottom, both sides will also be tested. The wet coated samples will be dried in a gravity convection oven, with curing curves generated according to the Tg of the prepared PHA determined in Objective 2. Film formation and interaction with the paper substrate will be characterized by scanning electron microscopy, andcontact angles will be measured using a goniometer. Packaging material coated with PHA will be evaluated for resistance to oil, water, and grease, as well as water vapor and oxygen transmission rates. Resistance to water absorption will be measured using the Cobb water absorption test. Resistance to grease absorption will be measured using the Kit grease resistance test. Moisture vapor transmission rateand oxygen transmission rate will be measured. Heat-sealability of the coated paper will be evaluated with a laboratory heat sealer with varying time and sealing temperature. Preliminary evaluation of recyclability of the coated papers will be done using the testing procedure proposed by Su et al. (2012) to determine the repulpability index.EvaluationMetrics: Form water-based PHA dispersions with ≥25% solids concentrations. Test their applicability to paper products using industry-standard equipment and testing procedures. Demonstrate coatings offer desirable barrier properties: <10 g/m2-day MVTR, 1-15.5 cc/m2day OTR, <10% weight pickup for oil or water.