Scale-Up of the Downstream Process for Polyhydroxyalkanoate Copolymer P(HB‑co-HHx) Extraction with Nonhalogenated Solvents

Abstract

Biobased and biodegradable polyhydroxyalkanoates (PHAs) are promising alternatives to common plastics. Due to their high production costs, only a minimal share of global plastic production is composed of PHA. A major contributor to the high costs minimizing the potential to occupy a larger market share is the downstream process. To obtain high recovery yields and pure products, most approaches rely on large amounts of solvents. While short-chain-length PHA (scl-PHA) is poorly soluble in nonhalogenated solvents, medium-chain-length PHA (mcl-PHA) was shown to be soluble in nonhalogenated solvents. In this study, an approach to recover poly(hydroxybutyrate-co-hydroxyhexanoate) with acetone and 2-propanol was scaled up 30-fold to 300 g of lyophilized cells per recovery cycle. High PHA purities of 90–100 % were reached from extractions at moderate temperatures from 30–58 °C. In two-stage extractions, up to 100 % PHA was recovered, while the molecular weight was not reduced. Solvents were recovered by distillation in a concentration step and after precipitation. Furthermore, the material properties were analyzed. PHA recovered from the distillation bottom had an increased HHx content compared to the first and second extractions using recovered solvents and was of low purity, indicating efficient and pure precipitation of the recovered PHA during the 2-stage extractions

Polyhydroxyalkanoate production from animal by‐products: Development of a pneumatic feeding system for solid fat/protein‐emulsions

“…Nevertheless, it is anticipated that the influence of residual lipids is neglectable when a non‐halogenated solvent‐based downstream processing is applied, which was shown for high‐purity P(HB‐ co ‐HHx) recovery from R . eutropha cells grown on plant oil and waste animal fat (Riedel et al, 2013 ; Thiele et al, 2021 ).…”

“…We showed that the bacteria efficiently take up the substrate, and an optimized C/N ratio will allow no residual lipids that potentially interfere with the downstream. Nevertheless, it is anticipated that the influence of residual lipids is neglectable when a non-halogenated solvent-based downstream processing is applied, which was shown for high-purity P(HB-co-HHx) recovery from R. eutropha cells grown on plant oil and waste animal fat (Riedel et al, 2013;Thiele et al, 2021).…”

Tailoring the HHx monomer content of P(HB-co-HHx) by flexible substrate compositions: scale-up from deep-well-plates to laboratory bioreactor cultivations

“…Molecular weight distribution of the PHA polymers was determined by size exclusion chromatography (SEC) from CDW samples as described previously ( Thiele et al, 2021 ).…”