Enhancing the 3‐hydroxyvalerate component in bioplastic PHBV production by Cupriavidus necator

Abstract

In the current context of global warming, the substitution of conventional plastics with bioplastics is a challenge. To take up this challenge, we must meet different technical and economic constraints. In the case of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), the technical properties can be modulated by varying the 3-hydroxyvalerate content. 3-Hydroxyvalerate (3-HV) enhancement is an issue; therefore, simultaneous evaluation of several 3-hydroxyvalerate-enhancing substrates through fractional factorial design of experiments is described. Eight substrates citric, valeric, propionic, and levulinic acids; propanol; pentanol; and sodium propionate were studied for 3-HV enhancement, and sodium glutamate was studied for biomass and polyhydroxyalkanoate (PHA) enhancement. The most efficient 3-hydroxyvalerate-enhancing factors were levulinic acid, sodium propionate, and pentanol; however, pentanol, at a concentration of 1 g/L, had an extremely negative influence on biomass production and the PHA content of cells. The effect of the inoculum nutrient composition on the final 3-HVcontent was also evaluated. These results showed that the most efficient combination for the production of high 3-HVcontent in PHBV was primary inoculum growth on mineral medium followed by fermentation for 48 h with levulinic acid and sodium propionate (at 1 g/L) as the only carbon sources. This allowed us to produce PHBV with a 3-HVcontent of 80 mol % and overall volumetric and specific productivities of 2 mg/L/h and 3.9 mg/g(CDW) /h, respectively, with the addition of only 2 g/L of inducing substances.

Improvement of the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) production by dual feeding with levulinic acid and sodium propionate in Cupriavidus necator

“…Moreover, the volumetric productivity reached 3.9 mg/L/hour, exceeding by 100% the previously reported results [23].…”

“…This allows the volumetric productivity of 3.9 mg/L/hour which is 100% greater than the previous results [23]. This method remains economical, as it uses only 3.5 g/L of carbon substrates for the production of PHBV with high, 80%, 3-HV content comparing to previously reported studies, with 20 g/L of inducing substrates [25,37].…”

“…To evaluate the most suitable proportions of the two, previously shown to be the most promising [23], 3-HV inducing substrates, the experiments with different initial concentrations ranging from 1 to 5 g/L of each, were performed (Fig. 1).…”

“…Recently, we have shown [23] that in the case of Cupriavidus necator DSM 545 the combination of levulinic acid with sodium propionate gave the best results for the enhancement of 3-HV content in PHBV. In the present study the interactions between those compounds, as well as their optimal concentrations and proportions were studied in order to enhance the PHBV production with high 3-HV content.…”

Metabolic engineering of Escherichia coli for the production of 1-propanol

“…Previous studies on the L-threonine metabolic pathway have shown that L-threonine dehydratase, encoded by the tdc operon (Hesslinger et al, 1998), as well as phosphotransacetylase and acetate kinase A/propionate kinase II, encoded by the pta and ackA genes, respectively, are involved in the degradation of L-threonine (Van Dyk and LaRossa, 1987). Recently, 2-ketoacids, intermediate metabolites in branched amino acid biosynthesis, have been successfully diverted to form structurally similar, but non-natural, alcohols Berezina, 2012;Mainguet and Liao, 2010;Peralta-Yahya and Keasling, 2010). Among them, 2-ketobutyrate, in particular, has been used as a starting point for the production of 1-butanol and 1-propanol (Shen and Liao, 2008).…”