Feasibility study of an alkaline-based chemical treatment for the purification of polyhydroxybutyrate produced by a mixed enriched culture

Abstract

This study focused on investigating the feasibility of purifying polyhydroxybutyrate (PHB) from mixed culture biomass by alkaline-based chemical treatment. The PHB-containing biomass was enriched on acetate under non-sterile conditions. Alkaline treatment (0.2 M NaOH) together with surfactant SDS (0.2 w/v% SDS) could reach 99% purity, with more than 90% recovery. The lost PHB could be mostly attributed to PHB hydrolysis during the alkaline treatment. PHB hydrolysis could be moderated by increasing the crystallinity of the PHB granules, for example, by biomass pretreatment (e.g. freezing or lyophilization) or by effective cell lysis (e.g. adjusting alkali concentration). The suitability of the purified PHB by alkaline treatment for polymer applications was evaluated by molecular weight and thermal stability. A solvent based purification method was also performed for comparison purposes. As result, PHB produced by mixed enriched cultures was found suitable for thermoplastic applications when purified by the solvent method. While the alkaline method resulted in purity, recovery yield and molecular weight comparable to values reported in literature for PHB produced by pure cultures, it was found unsuitable for thermoplastic applications. Given the potential low cost and favorable environmental impact of this method, it is expected that PHB purified by alkaline method may be suitable for other non-thermal polymer applications, and as a platform chemical.

Polyhydroxyalkanoate (PHA) purification through dilute aqueous ammonia digestion at elevated temperatures

“…Previous studies on alkali extraction have reported up to 96% PHA purity by using NaOH, and up to 99% when combined with SDS . When applied to the crude PHA from the present study, these methods led to 72% and 76% purity, respectively (Table ), giving further indication of the recalcitrance of the mixed microbial culture used for the PHA production.…”

“…Sodium hydroxide digestion, as well as combined NaOH and SDS digestion, were performed according to the protocols suggested by Jiang et al . Incubations were done using 100 mg of crude PHA and 4 mL of digestion solution, containing NaOH 0.2 mol/L or NaOH 0.2 mol/L with SDS 0.2% ( w / v ).…”

“…High PHA purity and recovery (> 90%) have been attained with some of these reagents (or combinations of them) both in pure strains and MMC . Nevertheless, the ester bonds of PHA are susceptible to hydrolysis and PHA degradation (reduction of molar mass) is usually reported as a significant drawback of these processes . In this sense, one of the most promising treatments so far is the use of dilute H 2 SO 4 followed by NaOCl.…”

Microbial community-based polyhydroxyalkanoates (PHAs) production from wastewater: Techno-economic analysis and ex-ante environmental assessment

“…glucose, methanol or acetic acid, contribute significantly to 48 the overall environmental impacts of the process, (Patel et al, 2005). 49 In order to address these issues on higher production costs and environmental impacts, a 50 microbial community engineering process for PHA production has been proposed, as an of the PHB is comparable to that of a commercial polymer (Jiang et al, 2015).…”

Recuperação e reutilização do carbonato de propileno empregado no processo de extração de poli(3-hidroxibutirato)

“…Por se tratar de um produto intracelular, o P(3HB) deve ser extraído da célula ao término do cultivo e estima-se que o impacto do custo de extração deste biopolímero, no custo total do processo de produção, possa representar mais de 50% do valor final do produto [4] . Os métodos utilizados no processo de extração de P(3HB) são: extração por solventes orgânicos como clorofórmio [5] ; carbonato de propileno [6,7] ; e dicloroetano [8] ; digestão enzimática [9,10] ; métodos mecânicos [11,12] e o uso de soluções aquosas de surfactantes e quelantes [13,14] . Dentre estes, os que fazem uso de solventes são os mais extensivamente utilizados.…”