Hemicellulosic hydrolysates copolymers

Thermal and viscosity-based characteristics of the P(3HB-co-3HV) samples produced from detoxified aspen hemicellulosic hydrolysate and levulinic acid are presented in Table I. The hemicellulosic hydrolysate-based samples displayed melting temperatures that decreased from 157 C to 98-103 C, with an increase in the mol % 3HV fraction of the copolymers. This T profile is relatively consistent with the pseudoeutectic behavior previously reported for other isodimorphic, P(3HB-co-3HV) copolymers (32,33). The isodimorphic properties displayed by these short-chain length copolymers relate to the similar size and crystalline lattice conformations of the monomers, which permit crystallization of polymer chains within either the 3HB or 3HV lattices (33). The Tm pattern determined for W. eutropha-der wQd P(3HB-co-3HV) samples... 

Table 1. Physical characteristics of P(3HB-cii-3HV) copolymers produced by Burkholderia cepacia from detoxified NREL CF/aspen-based hemicellulosic hydrolysate and levulinic acid.

The P(3HB-co-3HV) polymer has been a primary focus, because compared to P(3HB), the copolymer has physical and mechanical properties more conducive to melt-processing and subsequent commercial application. Investigators (Keenan et al, 2005 Nakas et al, 2004) have demonstrated the conversion of steam-exploded (aqueous) and organic solvent-extracted ( organosolv ) hemicellulosic hydrolysates (National Renewable Energy Laboratory, NREL, Golden, CO) to P(3HB-co-3HV) copolymers using levulinic acid as a cosubstrate (see Table 9.3). 

Table9.3 Physical-chemical characteristics of P(3HB-co-3HV) copolymers produced by shake-flask cultures of Burkholderia cepacia from hemicellulosic hydrolysate and levulinic acid as renewable, forest-based substrates and cosubstrates, respectively...

C5 hemicellulosic hydrolysates, produced by the NREL Clean Fractionation procedure, have been detoxified by methods related to the TVA detoxification procedure (Strickland and Beck, 1984). With the appropriate addition of an organic acid cosubstrate, levulinic acid, also produced from renewable feedstocks, we have produced P(3HB-co-3HV) copolymers possessing physical and chemical properties that are potentially useful for application as industrial bioplastics. Thermal characteristics and viscosity-derived molecular masses of a set of P(3HB-co-3HV) samples produced microbially from detoxified hemicellulosic hydrolysate and levulinic acid, are presented in Table 9.3. 

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