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ARS Home Pacific West Area Albany, California Western Regional Research Center Bioproducts Research Research





- McMahan, Colleen
- Chen, Grace
- 2023
- 2022
- 2021
- 2020
- Publications
- Product Quality and New Uses (306)

Research Project: **Location:
                            Bioproducts Research** Project Number: 2030-21410-022-000-D
                        
                        Project Type: In-House Appropriated Start Date: Apr 13, 2020
                        
                        End Date: Apr 12, 2025 **Objective:**
                        
                        Objective 1:  Genetically modify guayule for improved commercial rubber yields. 
Sub-objective 1A:  Over-express enzymes and proteins involved in natural rubber synthesis and accumulation in guayule, including components of the rubber transferase complex. 
Sub-objective 1B:  Increase natural rubber yield in guayule through controlled expression of transcription factors related to plant stress response. 
Sub-objective 1C.  Apply CRISPR/Cas9 technology to improve rubber yield in guayule. 

Objective 2:  Develop environmentally sustainable, commercially viable processes for fractionation and modification of guayule resin co-product into higher value products. 
Sub-objective 2A:  Enrich the high-value terpene fraction of guayule resin via  environmentally-friendly extraction and filtration processes. 
Sub-objective 2B:  Chemically modify guayule resin components to enhance their market value. 

Objective 3:  Enable marketable natural rubber composites incorporating food waste and byproducts. 
Sub-objective 3A:  Evaluate the use of heat-treated agricultural residues as bio-based reinforcing fillers in natural rubber compounds. 
Sub-objective 3B:  Assess the feasibility of using meat-processing byproducts and other agricultural residues as bio-based rubber compound additives. 
Sub-objective 3C: Develop bio-based antioxidants for stabilization of natural rubber and resin. **Approach:**
                        
                        Sub-objective 1A:  Over-express enzymes and proteins involved in natural rubber synthesis –Co-expression of genes associated with the Rubber Transferase and the MVA pathway will provide targets for preparation of a vector using GAANTRY technology that can insert  multiple transgenes simultaneously into plants. We will generate at least 10 independent transformed guayule lines using Agrobacterium-mediated transformation. Transgene insertion will be confirmed, and genotype and phenotype analysis performed.  

Sub-objective 1B:  Controlled expression of transcription factors – We will construct transformation vectors, overexpressing transcription factors.  Guayule transformation, transgene confirmation, transgene expression, and other phenotypes including rubber content will be determined.

Sub-objective 1C.  Apply CRISPR/Cas9 technology to improve rubber yield. – Using plant codon optimized synthetic Cas9 nuclease, to reduce off-target effects, Agrobacterium-mediated transformation of guayule will be performed to target the reporter gene GUS (ß-glucuronidase). Once the Cas9 is proven to be functional in guayule, we will target the AOS1 for gene editing. Transgenic lines will be further evaluated by standard methods.

Sub-objective 2A:  Enrich the high-value terpene fraction of guayule resin –The utility of filtration technology for fractionation of guayule resins will be evaluated, with a focus on green solvents and low temperature processing.

Sub-objective 2B:  Chemically modify guayule resin components – 
We will determine if saponification and methanolysis of complex guayule resin mixtures can/should be applied as a fractionation strategy, as a means to valuable products. 

Sub-objective 3A:  Evaluate the use of heat-treated agricultural residues –
We will conduct torrefaction of the guayule bagasse and other crop residues. Natural rubber composites will be prepared and characterized using with the torrefied biobased fillers compared to conventionally used fillers. 

Sub-objective 3B:  Assess the feasibility of using agricultural residues –
We will focus on protein sources from agricultural operations, initially meat by-products. Materials will be characterized for chemical and physical properties, and protein stability. Model natural rubber compounds will be formulated in which commercial meat by-products will be added to, or used in place of, synthetic anti-degradants and vulcanization aids, and the impact on compound performance assessed.

Sub-objective 3C: Develop bio-based antioxidants –
We will determine the efficacy of in vivo stabilization of guayule rubber by tocopherols, and ex vivo use of biobased antioxidants for guayule extraction processing and compounding.


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