A novel sustainable PHA downstream method

Abstract

A proposed greener approach for extraction of PHAs in comparison to methods using hazardous solvent.

Current trends in medium‐chain‐length polyhydroxyalkanoates: Microbial production, purification, and characterization

“…Although solvent extraction is a significantly efficient method, it is disadvantageous from an economic and environmental point of view because a large volume of toxic solvents is required. Therefore, for mcl‐PHA extraction, a comprehensive screening should be done to evaluate green and sustainable solvents, such as hydrophobic natural deep eutectic solvent (NADES), which exhibited a PHA recovery value and purity of 42% and 99%, respectively [ 68 ]. NADES comprises various naturally occurring or food‐grade components mixed in specific proportions to create a eutectic mixture with unique solvent properties.…”

A Novel Strategy for Extraction of Intracellular Poly(3-Hydroxybutyrate) From Engineered Pseudomonas Putida Using Deep Eutectic Solvents: Comparison with Traditional Biobased Organic Solvents

“…Furthermore, sonication was applied for either 1 or 2 min (experiments were carried out in triplicate). Conditions were tested with the use of a full factorial experimental design with the program MODDE 7 and Bradford assay to determine efficiency of disruption indirectly by protein concentration [21]. The PHB containing biomass pre-treatment in this work included the following steps: (i) Equal amounts of wet biomass were re-suspended in 6 ml hypotonic lysis buffer containing lysozyme and were left to incubate for set amount of time, (ii) after incubation some of the cell samples were sonicated for a set amount of time (0 or 2 min), (iii) 1 ml of the cell suspension was transferred to falcon tubes and diluted with 9 ml lysis buffer with lysozyme in different concentrations (0.5 mg/ml, 1.75 mg/ml and 3 mg/ml), (iv) Bradford assay was performed to assess the disruption efficiency by measuring protein release as compared to an un-disrupted control sample.…”

“…Hence, the method also requires that special care has to be taken when it comes to worker safety and solvent disposal [12,19]. Furthermore, after extraction, PHA purification usually requires the addition of a PHA anti-solvent in large volumes, of up to 10 times the volume of the original PHA solution, to precipitate the PHA [21][22][23].…”

“…This reduces the melting point of the mixture significantly with respect to its individual components, which is what deep in the NADES acronym refers to [33][34][35]. As NADESs are cheap to make and have low toxicity, they have gained popularity for many different applications in recent years, including for extraction and purification processes [21,36]. Furthermore, NADESs exhibit some of the same characteristics as detergents, they can also help to disrupt cells, potentially making pre-treatment less necessary and increasing extraction efficiency at lower temperatures.…”

Chlorine-free Extractions of Mixed-Culture Polyhydroxyalkanoates Produced from Fermented Sewage Sludge at Pilot Scale

“…The other procedure for the polymer recovery is based on chemical solubilization of non-PHA cell matrix (NPCM) with strong oxidant, typically NaClO and H 2 O 2 , or bases, mainly NaOH water solution, as well as enzymatic digestion. , However, the use of sodium hypochlorite also presents drawbacks due to the toxicity of potentially formed halogenated compounds and its difficult removal from the polymer . The combination of parallel or sequential methods have been proposed in order to increase the recovery yields and PHA purity without compromising the original polymer features by harsh extraction conditions. , For instance, preliminary cell disruption has been obtained by bead milling, mechanical mastication, sonication, and supercritical carbon dioxide treatment. − Mixed NPCM digestion or PHA solubilization procedures, including treatment with NaOH solution and sodium dodecyl sulfate (SDS), NaClO solution and SDS, NaClO and DMC, have been reported. − Furthermore, depending on the desired purity of the PHAs for their intended application, additional purification stages may be implemented, such as the precipitation the solubilized polymer using a nonsolvent . However, despite the considerable volume of literature encompassing these extraction methods, the comparison, evaluation, and selection of the most advantageous methodologies remain complex, challenging, and laborious.…”