Research Project: Zero Waste Agricultural Processing

Location: Bioproducts Research

2022 Annual Report

Objectives
Food processing losses can represent up to 40 percent of the initial harvest, resulting in significant environmental and economic costs. With stakeholders like the Almond Board of California committed to achieving zero waste, we aim to create viable bioproducts from agricultural byproducts, everything from field to table. The first objective is to add value to a low-value almond processing coproduct, the hulls, which are the bitter, but sugar-rich fruit of the almond tree, by: (1) creating a phenolic-rich sweetener for human consumption; (2) extracting sugar from almond hulls for use in bee diets during the winter, and (3) developing cost-effective carbon feedstock for fermentation that produces bioplastics and specialty chemicals. With a commercial partner we will optimize a novel fermentation process to convert food waste (including hulls) into a commercially-viable family of bioplastics specifically polyhydroxyalkanoates (PHA) using the latest techniques in biotechnology. Objective 1: Develop sustainable technologies toward “zero waste” production by converting food waste, byproducts and under-utilized biomass streams into marketable plastics, specialty chemicals, additives, and active agents. • Sub-objective 1A. Add value to almond hulls. • Sub-objective 1B. Convert food waste and under-valued byproduct streams into bioplastics]. • Sub-objective 1C. Convert pectin-rich citrus peel waste, sugar beet biomass, and almond hulls into aldaric acid and aldonate bioproducts. Objective 2 focuses on optimizing new uses for underutilized agricultural fibers. In collaboration with several commercial partners, we plan to scale up torrefaction (heating biomass to 200-300 'C), to convert tree nut shells and hemp residue into functional fillers that will improve commodity plastics. We also propose to convert underutilized polysaccharides like pectin, alginate, and xylan were isolated from enzyme conversion processes into industrially-relevant environmentally friendly diacids such as aldaric acid for use as solvents in homecare products. Our group has developed a wide array of enzymes to deconstruct plant cell walls. These enzymes will be used, via combinatorial enzymatic strategies and in vitro reaction schemes, to create “designer oligosaccharides” and green chemicals that meet specific marketable needs. Objective 2: Optimize end-use technology for underutilized agricultural fibers, including straw residue, bagasse, and grasses by developing commercially-viable chemicals and nanoparticles for novel applications including nanocomposites. • Sub-objective 2A. Apply thermochemical conversion technology to add value to tree nut shells and underutilized crop residues including hemp. • Sub-objective 2B. Convert biomass into designer oligosaccharides using combinatorial enzyme technology.

Approach
Objective 1: Develop sustainable technologies toward “zero waste” production by converting food waste, byproducts and under-utilized biomass streams into marketable plastics, specialty chemicals, additives, and active agents. Sub-objective 1A. Add value to almond hulls. Sub-objective 1B. Convert food waste and under-valued byproduct streams into bioplastics. Sub-objective 1C. Convert pectin-rich citrus peel waste, sugar beet biomass, and almond hulls into aldaric acid and aldonate bioproducts. Objective 2: Optimize end-use technology for underutilized agricultural fibers, including straw residue, bagasse, and grasses by developing commercially-viable chemicals and nanoparticles for novel applications including nanocomposites. Sub-objective 2A. Apply thermochemical conversion technology to add value to tree nut shells and underutilized crop residues including hemp. Sub-objective 2B. Convert biomass into designer oligosaccharides using combinatorial enzyme technology.

Progress Report
In support of Sub-objective 1A, ARS researchers in Albany, California, are working to add value to almond coproducts by removing bitter tannins from almond hull sugars. Almond hull sugars are rich in antioxidants and nutraceutical components that could benefit human health and open new markets for almond hulls, which are not eaten because of their bitter-tasting phenolic tannins. While certain cultures eat almond hulls, their bitter taste limits their market appeal. ARS researchers in Albany, California, developed a safe and nutritious method to remove the bitter tannins from almond hull sugars by precipitation with proteins including casein, zein, gluten, and fish gelatin. Fish gelatin at approximately 1% proved most effective, removing up to 85% of the phenolic tannins while leaving most of the free sugars and minimizing the loss of health-promoting antioxidants. This information increases the commercial potential of almond hull sugars as a sweetener that could displace, for example, high fructose corn sugars in processed foods. In support of Sub-objective 1B, polyhydroxyalkanoate (PHA) biopolymers are being optimized for specific market needs by matching culture conditions with asked-for specifications, such as degree of compostability and the ability to form safe and sustainable adhesives. In response to international regulations that could limit U.S. exports of fruits, ARS researchers in Albany, California, in collaboration with industry partners are developing single-use packages and stickers, termed Product Look-Up (PLU) labels, that are sustainably produced and fully compostable. The team has focused on creating home-compostable adhesives that meet the American Society for Testing and Materials (ASTM) standards and could be applied industrially as PLU labels for use on fruit for export markets. Adhesives from a series of biopolymers, including a particularly “sticky” formulation of polyhydroxyalkanoates (PHA), were tested in industrial labelling conditions. Research to optimize these adhesives in conjunction with a sustainable laminate formulation continues. In support of Sub-objective 2A, advanced thermochemical treatments are being developed to add value to under-utilized biomass sources to create advanced biomaterials. ARS researchers in Albany, California, have carried out research to commercialize pyrolyzed almond shells for advanced applications such as in lightweight composites, natural gas storage, batteries, and ultracapacitors. In one application, the effect of raw and torrefied rice hulls on PHA biocomposites was investigated. The composites were analyzed for flexural and tensile strength with the aim to develop polyhydroxybutyrate (PHB) composite blends suitable for consumer plastic applications. For advanced electronic applications, research continues to optimize thermal treatments on pyrolyzed almond shells to provide an alternate high-value market for the almond industry. In support of Sub-objective 2B, ARS researchers in Albany, California, have been working with industrial partners including waste handlers to optimize the value of oligopolysaccharides isolated from under-valued biomass sources. Recent progress includes isolation and characterization of nanocrystalline cellulose fibrils from (1) municipal solid waste (MSW), (2) almond coproducts, and, notably, (3) shredded bank notes from the United States Treasury. Each of these sources represent under-valued biomass sources that could add to greenhouse gas production if allowed to go to landfills. Research continues to build economic models that converts these polysaccharide-rich streams into marketable bioproducts, including as composite materials in plastic products.

Accomplishments
1. Reversible antibiotics to treat bovine mastitis. Bovine mastitis caused by infection of milk ducts in dairy cattle, which results in significant losses to the industry because milk and meat, from even treated cattle, cannot be marketed for consumption. Treatments result in significant antibiotic use, with high doses of iodine, copper sulfate, and formalin, highlighting the need for safer alternatives that do not taint milk or lead to antibiotic resistance. ARS researchers in Albany, California, developed a novel reversible biocide derived from natural products that has demonstrated excellent efficacy against pathogens that cause mastitis. They showed that a reversible antibiotic (biocide) was formed by joining benzaldehyde with guanyl hydrazones. When formulated in a mastitis balm this reversible biocide dramatically reversed the onset of mastitis for clinically affected animals, with results matching the efficacy of high doses of iodine, the industry standard. Further research showed that, upon dilution, the benzaldehyde guanyl hydrazones antibiotics de-coupled back to benign, farm-safe ingredients, thus minimizing the development of antibiotic resistance due to residual build-up of unwanted chemicals.

Review Publications
Rafique, N., Bashir, S., Khan, M., Hayat, I., Orts, W.J., Wong, D. 2021. Metabolic engineering of Bacillus subtilis with an endopolygalacturonase gene isolated from Pectobacterium. carotovorum, a plant pathogenic bacterial strain. PLoS ONE. 16(12). Article e0256562. https://doi.org/10.1371/journal.pone.0256562.
Ma, Y., Ma, Y., Yu, Z., Chiou, B., Liu, F., Zhong, F. 2021. Calcium spraying for fabricating collagen-alginate composite films with excellent wet mechanical properties. Food Hydrocolloids. 124. Article 107340. https://doi.org/10.1016/j.foodhyd.2021.107340.
Zhang, T., Yu, Z., Yun, M., Chiou, B., Liu, F., Zhong, F. 2021. Modulating physicochemical properties of collagen films by cross-linking with glutaraldehyde at varied pH values. Food Hydrocolloids. 124. Article 107270. https://doi.org/10.1016/j.foodhyd.2021.107270.