Pilot-scale Production of Functionalized mcl-PHA from Grape Pomace Supplemented with Fatty Acids

S. Follonier, R. Riesen and M. Zinn

Abstract
Bioprocess optimization is a prime target to decrease the cost of functionalized medium-chain-length poly(3-hydroxyalkanoate) (mcl-PHA). We have already demonstrated at the laboratory scale that the pomace of white wine grapes is a promising growth substrate for the biosynthesis of mcl-PHA that is both cheap and does not compete with food and land use. Here, we report the scale-up of a 2-step, 100 L bioprocess with Pseudomonas putida KT2440 involving: (1) a batch growth phase on extract of Gewürztraminer grape pomace, and (2) a fed-batch polymer accumulation phase with a linear feed of 50 mol % octanoic acid and 50 mol % 10-undecenoic acid. With this approach, we achieved a cell dry weight of 14.2 ± 0.3 g L–1 containing 41.1 ± 1.3 wt % of poly(3-hydroxyoctanoate-co-3-hydroxy-10-undecenoate) with 53 mol % and 47 mol % of saturated and unsaturated monomers, respectively. The molecular weight (Mw) was 139 000 Da (PDI = 1.97) and DSC analysis showed a Tg of –45.5 °C but no Tm thus indicating a completely amorphous polymer.

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Keywords
polyhydroxyalkanoate, mcl-PHA, scale-up, pomace, functionalized PHA