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Diverse sources of wastewater organic carbon can be microbially funneled into biopolymers like polyhydroxybutyrate (PHB) that can be further valorized by conversion to hydrocarbon fuels and industrial chemicals. We report the vapor-phase dehydration and decarboxylation of PHB-derived monomer acids, 3-hydroxybutyric acid (3HB) and crotonic acid (CA), in water to propylene over solid acid catalysts using a packed-bed continuous-flow reactor. Propylene yields increase with increased Brønsted acidity of catalysts, with amorphous silica–alumina and niobium phosphate yielding 52 and 60 %C (percent feedstock carbon, max 75 %C) of feedstock 3HB and CA, respectively; additional products include CO 2 and retro-aldol products (acetaldehyde and acetic acid). Deactivation studies indicate progressive and permanent steam deactivation of amorphous silica–alumina, while re-calcination partially recovers niobium phosphate activity. Experiments demonstrating sustained reactor operation over niobium phosphate provide a promising technology pathway for increasing valorization of organic-rich wastewater.
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Bioplastic degradation by a polyhydroxybutyrate depolymerase from a thermophilic soil bacterium
Abstract As the epidemic of single‐use plastic worsens, it has become critical to identify fully renewable plastics such as those that can be degraded using enzymes. Here we describe the structure and biochemistry of an alkaline poly[(R)‐3‐hydroxybutyric acid] (PHB) depolymerase from the soil thermophileLihuaxuella thermophila. Like other PHB depolymerases or PHBases, theLihuaxuellaenzyme is active against several different polyhydroxyalkanoates, including homo‐ and heteropolymers, butL. thermophilaPHB depolymerase (LtPHBase) is unique in that it also hydrolyzes polylactic acid and polycaprolactone.LtPHBase exhibits optimal activity at 70°C, and retains 88% of activity upon incubation at 65°C for 3 days. The 1.2 Å resolution crystal structure reveals an α/β‐hydrolase fold typical of PHBases, but with a shallow active site containing the catalytic Ser‐His‐Asp‐triad that appears poised for broad substrate specificity.LtPHBase holds promise for the depolymerization of PHB and related bioplastics at high temperature, as would be required in bioindustrial operations like recycling or landfill management.
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- Award ID(s):
- 1817796
- PAR ID:
- 10377097
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Protein Science
- Volume:
- 31
- Issue:
- 11
- ISSN:
- 0961-8368
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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