Optimization of Growth Conditions to Enhance PHA Production by Cupriavidus necator

Abstract

The accumulation of polyhydroxyalkanoates (PHAs) by microorganisms usually occurs in response to environmental stress conditions. Therefore, it is advantageous to choose two-step cultivation. The first phase is aimed at maximizing biomass production, and only in the second phase, after setting the suitable conditions, PHA production starts. The aim of this work was to optimize the composition of the minimal propagation medium used for biomass production of Cupriavidus necator DSM 545 using the response surface methodology (RSM). Based on the results from the search for optimization limits, the glucose concentration, the ammonium sulfate concentration and the phosphate buffer molarity were chosen as independent variables. The optimal values were found as follows: the glucose concentration 10.8 g/L; the ammonium sulfate concentration 0.95 g/L; and the phosphate buffer molarity 60.2 mmol/L. The predicted biomass concentration was 4.54 g/L, and the verified value was at 4.84 g/L. Although this work was primarily focused on determining the optimal composition of the propagation medium, we also evaluated the optimal composition of the production medium and found that the optimal glucose concentration was 6.7 g/L; the ammonium sulfate concentration 0.60 g/L; and the phosphate buffer molarity 20 mmol/L. The predicted PHB yield was 54.7% (w/w) of dry biomass, and the verified value was 49.1%.

Optimizing Hexose Utilization Pathways of Cupriavidus necator for Improving Growth and L-Alanine Production under Heterotrophic and Autotrophic Conditions

“…Additionally, several different types of carbon sources, such as acetate, citrate, and glycerol, for instance, can also be utilized by C. necator [ 30 ]. Under unbalanced culture conditions, like limitation of oxygen, phosphorus, or nitrogen, a large amount of PHB was accumulated in cells of C. necator as energy storage material [ 1 ]. The mineral media for C. necator were optimized in this study, especially increasing the nitrogen concentration and the proportion of trace elements, which accelerated the growth rate of the CnΔ6 strain and significantly shortened the logarithmic phase of autotrophic fermentation from 64 d to 15 d [ 11 ].…”

“…Cupriavidus necator H16 (formerly known as Ralstonia eutropha H16) is a chemolithoautotrophic Gram-negative bacterium that serves as a model organism for the natural synthesis of poly-β-hydroxybutyrate (PHB). It has been shown to accumulate up to 90% of PHB based on dry weight under restricted nutrition [ 1 ]. Its broad carbon source utilization spectrum, detailed genomic information, and efficient gene editing system [ 2 , 3 ] position C. necator as a promising candidate for applications in environmental protection and bio-resource conversion [ 4 ].…”

Alkaline-Tolerant Bacillus cereus 12GS: A Promising Polyhydroxybutyrate (PHB) Producer Isolated from the North of Mexico

“…These parameters (150 rpm, pH 8, 30 • C, and 4% inoculum) were probed, and the results of the optimization showed an increased PHB production, the values increasing by 0.65 g/L PHB and 14.2% PHB in the quantitative screening (Section 3.4) to 1.91 g/L PHB and 87.2% PHB (Table 6). Rond'ošová et al [50] optimized the medium for PHB production and obtained 49% PHB. As well, García et al [51] report 29% PHB using the Taguchi experimental design.…”

The biological and therapeutic assessment of a P(3HB‐co‐4HB)‐bioactive glass‐graphene composite biomaterial for tissue regeneration

“…Polyhydroxyalkanoates (PHAs) belong to the natural biopolymer family within the polyester group, comprised of recurring hydroxyalkanoates (HAs) monomers. These materials result from the fermentation of various microbes in controlled environments with limited nutrients such as nitrogen, magnesium, phosphorus, or oxygen, yet in abundance of carbon sources 6,7 . In these specific microbial growth conditions, carbon sources transform into PHAs, functioning as internal storage compounds for carbon and energy.…”