Project : USDA ARS

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Research Project: Bioproducts and Biopolymers from Agricultural Feedstocks

Location: Bioproducts Research

2021 Annual Report

Objectives
Objective 1 encompasses processing technologies primarily for cellulosic feedstocks including hemp, a potential new specialty crop in the U.S. Research on objective 1 will focus on fiber-based packaging, particularly insulative and/or cushioning foam packaging and nanofiber films and composites. Objective 2 encompasses a broader range of feedstocks and includes starches and other carbohydrates beyond starch and cellulose as well as polyhydroxyalkanoates that are produced by bacteria. The primary objective is to utilize renewable polymers that are degradable in both garden compost and marine environments to make bioproducts designed for single-use food and packaging items. Objective 3 focuses on sustainable solutions for chemical products, particularly antibiotics, that are a growing health or environmental concern. The focus will be to use small molecules that bind or associate at critical concentrations to form active complexes with specific functions. Below the critical concentrations, the active complexes dissociate into benign molecules. Objective 1: Enable new technologies to manufacture fiber/nanofiber-based bioproducts. • Sub-objective 1A: Enable new technologies for making fiber-based foam products with moisture and grease/oil resistance. • Sub-objective 1B: Create consumer products utilizing hemp fiber. Objective 2: Enable new technologies for biopolymers and their blends. • Sub-objective 2A: Develop plastics and composites for consumer products that are readily degraded in marine and soil environments. • Sub-objective 2B: Develop microorganisms for novel biopolymer production. • Sub-objective 2C: Develop new technologies to process biopolymers into industrially-relevant products. Objective 3: Develop bioactive materials that are designed to minimize ecotoxicity and biocide resistance.

Approach
Hypothesis 1A: Fiber-based materials can be made into rigid, insulative foam products or non-foam composites with moisture and grease/oil resistance. Rigid foam samples will be made with agricultural fibers, foaming agent, and sizing agents. The rigid foam will be characterized by testing the mechanical and thermal properties of the foam. If the use of agricultural fibers is unsuccessful or too expensive, kraft fiber from wood pulp will be used in the study. Hypothesis 1B: The hypothesis statement will be provided by the scientist who fills the vacant position in the CRIS. Biomass left over from CBD extraction from various industrial hemp cultivars will be pulped and used as a source of nanofibers. Water soluble film formulations will be provided by our CRADA partner and treated with nanofibers to evaluate their effect on mechanical properties. If nanofibers from hemp do not desired properties, biomass resources provided by our cooperators from Brazil. Hypothesis 2A: Marine degradable polymers and composites can be processed into bioproducts including films, foams, and molded articles. We intend to promote crystallization of thermoplastic starch (TPS) during and after extrusion and molding as a means of enhancing moisture resistance and improving strength without reverting to chemical modification or blending. Commercial starches from various agricultural sources and with varying amylose:amylopectin ratios will be evaluated and formed into TPS using twin-screw extrusion. Blends of TPS and wood fiber, cellulose nanocrystals/nanofibrillar cellulose from hemp or corn stover will be prepared, processed by extrusion and/or film blowing, and characterized. Other biopolymers or mineral additives will be used in formulations if the properties of TSP are not acceptable. Hypothesis 2B: Microorganisms that use methane (methanotrophs) or other carbon sources (Bacillus subtilis) can be engineered to improve production processes and generate valuable biopolymer additives. We will use overexpression of targeted proteins to increase cell hydrophobicity in methanotrophs. If this approach is unsuccessful, the membrane proteins that target proteins regulate will also be singled out to change their expression. Hypothesis 2C: Active nutritional supplement can be produced at large scale by Bacillus megaterium.: B. megaterium strains within our own inventory will be used to produce poly-3-hydroxybutyrate (P(3HB)) trimers as active nutritional supplements. If insufficient quantities of 3HB trimer are produced, another strategy would be to isolate fungal or bacterial depolymerases for their ability to release trimers from P(3HB). Hypothesis 3: Judicious use of reversible actives (e.g. antimicrobials) will minimize negative human health effects, ecotoxicity and biocide resistance. We will incorporate reversible bonds in traditionally persistent chemicals such as cationic guanylhydrazones to minimize environmental toxicity and biocide resistance. If activity is affected by anionic additives, we will utilize hydroxamic acids.

Progress Report
In support of Sub-objective 1A, a simple process was developed for making fiber foam using a surfactant and rigorous mixing. A blender was used to disperse the fiber in an aqueous solution. The wet foam was mixed with various binders then deposited in a sheet mold followed by oven drying. The finished foam was comparable in compression strength to soft polyurethane foam. Binders such as starch increased the stiffness and compressive strength of foams. The foam density ranged from 0.02 to 0.05 grams per cubic centimeter depending on the amount of binder added to the formulation. The foam had thermal insulative properties comparable to polystyrene foam. The foam had very little moisture resistance and quickly dispersed when added to water. However, a new method was developed to improve moisture resistance. An invention disclosure was submitted detailing the methods used to make moisture resistant foams that were still lightweight and had good thermal insulative properties. This research supports the objective of developing new technologies for making fiber-based foam products with moisture and grease/oil resistance. Data collected on foam experiments were shared with stakeholders through written reports and Zoom meetings. Progress on Sub-objective 2A included the development of starch/fiber composites were developed that had superior tensile strength. The composites were prepared by uniformly dispersing softwood pulp fiber in a starch matrix. The composite material was formed into sheets by compression molding with heated platens. The finished, dry products could be rolled into large rolls and stored until ready for the molding step. The dry composite was prepared for compression molding by first prehydrating the film to about 15% moisture content. This amount of hydration made the composite very pliable and easy to mold into a finished article such as a plate or bowl. The compression mold was heated which effectively lowered the moisture content of the film and solidified the shape of the molded article. This research supports the objective of developing plastics and composites for consumer products that are readily degraded in marine and soil environments. Progress was made in developing composite materials with moisture/oil resistance. Currently, packaging is made using per- and polyfluoronated additives that confer moisture/oil resistance to food packaging. Starch/fiber composites were made using an alkyl ketene dimer additive. The additive effectively provided the composite materials with good moisture/oil resistance. Reversible guanylhydrazones were shown to be highly effective in nonionic surfactant-containing cleaning solutions, including a commercial product formula provided by our CRADA partner. Guanylhydrazones provided disinfectant-like activity (>4-log reductions of pathogenic bacteria) and passed preservative challenge testing (USP-51) at a very low level (0.2 wt. %), as confirmed by a third-party testing lab.

Accomplishments
1. Starch fiber composite resistant to oils, but susceptible to moisture. ARS researchers in Albany, California, in collaboration with scientists from an industrial partner developed a process for making a composite of starch and plant fibers that is both moisture and oil resistant. The starch/fiber composite is naturally resistant to oils but is susceptible to moisture. By incorporating a chemical sizing agent, the composite material exhibits very good moisture and oil resistance. This invention was developed as a sustainable/biodegradable alternative to perfluoro chemicals that are no longer permitted as sizing agents in food containers.

U.S. DEPARTMENT OF AGRICULTURE

Bioproducts Research: Albany, CA