|Ashby, Richard - Rick|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 8/13/2018
Publication Date: 11/26/2018
Citation: Ashby, R.D., Solaiman, D. 2018. Levulinic acid: A valuable platform chemical for the fermentative synthesis of poly(hydroxyalkanoate) biopolymers. In: Cheng, H.N., Gross, R.A., and Smith, P.B. (eds.). Green Polymer Chemistry: New Products, Processes, and Ap. Book Chapter. ACS Press, Washington DC, ACS Symposium Series 1310:339-354.
Interpretive Summary: Levulinic acid is a renewable chemical that can be easily produced from the sugars present in plant biomass. As such, it can be produced economically at a large-scale. Many chemical companies have focused their research efforts on using levulinic acid to chemically-produce various related molecules that have applications in the fuel, herbicide, polymer and solvent arenas. One potential use of levulinic acid that is only now garnering interest is as a microbial food source. Poly(hydroxyalkanoates) (PHA) are microbially-derived polyesters (plastics) that can be naturally degraded into carbon dioxide and water which makes them, from an environmental standpoint, more appealing in large-scale applications. Unfortunately, history has shown that producing these environmentally-benign plastics using microbes is prohibitively more expensive than their petrochemical equivalents thus limiting their use. By using levulinic acid in combination with other low-cost molecules such as glycerine (a coproduct from biodiesel synthesis), whey permeate (a byproduct of the cheese-making process), and/or xylose (a large volume sugar naturally present in plant biomass), specific PHA polymers can be produced with favorable properties at lower costs than previously achieved. By reducing the production costs, these microbially-derived plastics will become more economically competitive with petroleum-based plastics thus improving their application potential.
Technical Abstract: Levulinic acid (LVA) is a valuable platform chemical that can be produced from both 5-carbon and 6-carbon sugars. As such, lignocellulosic biomass is a rich source of sugars for the large-scale production of LVA. Because LVA is relatively cheap, it may be viewed as a promising feedstock for biological syntheses. Many bacterial strains have been shown to utilize LVA for the synthesis of polyhydroxyalkanoate (PHA) polymers however, only a few have been confirmed to use LVA in combination with other cheap, renewable feedstocks (e.g., glycerine, whey permeate and xylose) to produce copolymeric PHA polymers. This chapter focuses on our work as well as that of others in the synthesis of copolymers consisting of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) (P-3HB-co-3HV) from separate mixtures of LVA with glycerine, whey permeate, and xylose. By utilizing LVA in conjunction with other cheap feedstocks, the economics of PHA production can be improved making these materials more attractive for large-scale use.