The Use of Azohydromonas lata DSM 1122 to Produce 4-hydroxyvalerate-Containing Polyhydroxyalkanoate Terpolymers, and Unique Polymer Blends from Mixed-Cultures with Burkholderia sacchari DSM 17165
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Azohydromonas lata DSM 1122 was utilized to synthesize short-chain-length (scl-) polyhydroxyalkanoate (PHA) terpolymers containing 3-hydroxybutyric (3HB) acid, 3-hydroxyvaleric (3HV) acid, and 4-hydroxyvaleric (4HV) acid from mixtures of glucose (GLC; 1 wt%) and levulinic acid (LevA; 0–0.4 wt%). LevA media concentrations greater than 0.4% completely inhibited cellular growth. At LevA concentrations ≤ 0.4%, the 3HV polymer content remained constant (3–5 mol%). The 4HV content was two-fold higher in the polymers derived from the 0.2% LevA-containing cultures reaching a maximum of 9 mol% (vs. 4 mol% in the 0.4% LevA-containing cultures). Polymer molecular weights (based on number-average molecular weight, Mn) were smallest (Mn = 240,000 g/mol) when synthesized in the presence of 0.2% LevA. At 0.4% LevA and at 1% GLC the average Mn values were 43% and 87% larger than the polymers synthesized in the presence of 0.2% LevA, respectively. Mixed-cultures containing A. lata and Burkholderia sacchari DSM 17165, a known poly-3-hydroxybutyrate-block-3-hydroxyvalerate (P3HB-block-3HV) producer, using LevA media concentrations ≤ 0.4% and staggered inoculations resulted in scl-PHA polymer mixtures with improved tensile properties. The results of this study show that LevA can be utilized in combination with simple sugars to produce unique scl-PHA terpolyesters and scl-PHA mixtures with enhanced properties.
KeywordsAzohydromonas lata Levulinic acid Terpolyesters 4-Hydroxyvalerate Mixed cultures
The authors gratefully acknowledge Nicole Crocker, Jennifer Thomas, and Nick Latona for their technical assistance throughout the study.
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