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The aim of this work was to produce the biopolymer polyhydroxybutyrate (PHB) from industrial flue gas as CO 2 source and electrolysis originating hydrogen via microbial electrosynthesis. Besides the laboratory experiments, the experiments were carried out under industrial conditions directly on-site in a cogeneration plant. We were able to demonstrate that the use of flue gas as a CO 2 source has no detectable negative effect on bacterial growth and PHB production in comparison to a pure gas mixture. In an electrochemical H-cell 333 ± 44 mg L−1 PHB were obtained, which corresponds to a PHB content of 43 ± 3 % of the cell dry weight. By using flue gas for the production of the biopolymer PHB, not only CO 2 emissions are reduced, but also possible environmental pollution from non-biodegradable plastics. To the best of our knowledge, this is the first time that the production of PHB from flue gas has been demonstrated using Cupriavidus necator. • First-ever production of polyhydroxybutyrate from flue gas with Cupriavidus necator. • Microbial growth and product formation not affected by flue gas components. • Using CO 2 as a resource while reducing greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHA) are biodegradable polyesters that can be produced from renewable resources. However, PHA biomanufacturing is costly compared to petrochemical-based plastics. A promising solution consists of using cassava (Manhiot esculenta) waste, abundant biomass in developing countries, as a carbon source for PHA production. This study involved characterising untreated and acid-hydrolysed cassava peel (CP) to confirm the degradation of polysaccharides into fermentable sugars after pre-treatment. A chemical and biological integrated process was developed, optimising the pre-treatment using a central composite design. The highest conversion of CP into reducing sugars was 97% (w/w) using 3 M H 2 SO 4 , 120 min and 90 ºC. The ability of Cupriavidus necator to grow on CP hydrolysate and produce PHA was screened resulting in up to OD 600 15.8 and 1.5 g/L of PHA (31% (g PHA /g DCW)). Flow cytometry allowed rapid, simple, and high-throughput assessment of PHA content. These findings pave the way for developing a biorefinery platform for PHA production from cassava waste. [Display omitted] • Cassava peel (CP) is a renewable resource with great valorisation potential. • CP was converted into polyhydroxyalkanoates (PHA) via chemical and microbial routes. • Optimisation of CP acid hydrolysis resulted in 97% conversion into reducing sugars. • The integration of chemical and biological processes resulted in 31% of PHA. • Flow cytometry allowed rapid, simple and high-throughput assessment of PHA content. [ABSTRACT FROM AUTHOR]

Poly(3-hydroxybutyrate) (PHB) is one of the most well-known biodegradable and biocompatible biopolymers produced by prokaryotic microorganisms. It belongs to the family of polyhydroxyalkanoates (PHAs), and it has gained significant attention in recent years due to its potential as a sustainable alternative to traditional petroleum-based plastics. Cupriavidus necator has been identified as a potential producer of PHB for industrial applications due to its ability to produce high amounts of the polymer under controlled conditions, using a wide range of waste substrates. In this study, the ability of Cupriavidus necator DSM 545 strain to produce PHB was tested in a fed-batch strategy providing two different organic substrates. The first is a sugar-based syrup (SBS), derived from cereal waste. The second is an acetate-rich medium obtained through CO 2 -H 2 fermentation by the acetogenic bacterium Acetobacterium woodii. The carbon sources were tested to improve the accumulation of PHB in the strain. C. necator DSM 545 proved to be able to grow and to perform high accumulation of biopolymer on waste substrates containing glucose, fructose, and acetate, reaching about 10 g/L of PHB, 83% of biopolymer accumulation in cell dry mass, in 48 h of fed-batch fermentation in 0.6 L working volume in a bioreactor. Moreover, a Life Cycle Assessment analysis was performed to evaluate the environmental impact of the process converting the sugar syrup alone and the integrated one. It demonstrated that the integrated process is more sustainable and that the most impactful step is the PHB production, followed by the polymer extraction. • Cupriavidus necator DSM 545 growth and poly(3-hydroxybutyrate) biosynthesis using a sugar-based syrup from cereal waste. • C. necator DSM 545 growth and PHB biosynthesis providing a cereal waste substrate and acetate from gas fermentation. • Environmental evaluation of the integrated bioprocess for PHB production through the Life Cycle Assessment. [ABSTRACT FROM AUTHOR]

CbnR, a LysR-type transcriptional regulator fromCupriavidus necatorNH9, activates the transcription of chlorocatechol-degradative enzymes. To activate the transcription, CbnR needs to bind not only to thecbnApromoter but also to the inducer. In this study, the transcriptional activity and DNA-binding activity of twenty-five mutants of CbnR were analyzed. Of the 17 mutants of the DNA-binding domain, 11 mutants lost their ability to activate transcription. While most mutants without transcriptional activation did not show DNA-binding activity, Asn17Ala, Gln29Ala, and Pro30Ala retained DNA-binding activity, suggesting that transcriptional activation by CbnR requires more than its binding to promoter DNA. Of the 8 mutants of the regulatory domain, 6 mutants changed their responses to the inducer, when compared with wild-type CbnR. Interestingly, Arg199Ala and Val246Ala induced constitutive expression of thecbnApromoter without the inducer, suggesting that these mutations brought about a conformational change mimicking that induced by the inducer molecule. Mutational analysis of a LysR-type transcriptional regulator, CbnR, revealed critical amino acids in regulatory domain (A and B) and DNA-binding domain (C and D). [ABSTRACT FROM AUTHOR]

An abstract of the article "Production of Polyhydroxyalkanoates by Cupriavidus necator From Treated Olive Mill Wastewater" by Gonzalo A. Martinez and colleagues is presented.

Highly efficient polyhydroxybutyrate conversion into crotonic acid was achieved. Low temperature and no catalyst were used in the crotonic acid production. Renewed polyhydroxybutyrate was obtained by using crotonic acid and C. necator. High overall yield and low energy demand make this strategy feasible and promising. The recycling of polyhydroxybutyrate (PHB) via depolymerization-polymerization is here proposed and assessed for the first time. Effective depolymerization of PHB to crotonic acid through a thermolytic distillation at mild conditions (170 °C and 150 mbar), and without the need of any catalyst, gives a crotonic acid-enriched condensate (94% yield and 98% selectivity towards trans-crotonic acid) that was used without any further purification as a substrate for producing renewed PHB with a culture of Cupriavidus necator. The yield of PHB (0.6 g PHB per g of crotonic acid), final PHB content (63%), and PHB-molecular weight (1.5 MDa) confirmed the technical feasibility of this tandem approach, with a 55% overall yield. A preliminary evaluation of the energy consumption of various depolymerization approaches indicated that the thermolytic distillation consumes 20–25% less energy than previously reported methods; the energy requirement for producing crotonic acid from PHB waste with 50% moisture has a still acceptable energy demand (4 MJ/kg crotonic acid), comparable to the energy required for obtaining fermentable sugars (4.4 MJ/kg sugar) to be used for feeding bacteria that accumulate PHB. [Display omitted] [ABSTRACT FROM AUTHOR]

Replacement of substrate by utilizing renewable, sustainable, abundance, and low-costs carbon sources derived from agricultural waste enables the reduction of wastes in industry and simultaneously capacitate the production of value-added products. The total amount of sugar in the banana frond extract (BFE) was 42.7 g/L, which in part consist of 10.5 g/L fructose. The effect of various BFE concentration on the PHB production was determined by conducting the fermentation utilizing BFE ranging from 10% to 50% (v/v) at 30 °C, 200 rpm for 72 h of incubation. The fermentation with 40% (v/v) BFE resulted in the highest PHB content in biomass (32.1%) and PHB concentration (0.9 g/L). Furthermore, the production of PHB was also examined by comparing the fermentation with 40% (v/v) raw and sucrase enzyme pre-treated BFE, respectively. The fructose content in the enzyme pre-treated BFE after enzymatic hydrolysis was increased to 14.6 g/L. The fermentation with 40% (v/v) pre-treated BFE showed higher PHB content in biomass (37.4%) and PHB concentration (1.3 g/L) as compared to the 40% (v/v) original BFE. The result indicates that 40% (v/v) of enzyme pre-treated BFE can be utilized as an alternative renewable and sustainable carbon feedstocks for PHB production. • BFE can be utilized as an alternative sustainable carbon source for PHB production by C. necator H16. • Effect of various BFE concentration for 10, 20, 30, 40, and 50% (v/v) on the PHB production was examined. • Fermentation with 40% pre-treated BFE showed highest PHB content in biomass (37.4%) and concentration (1.3 g/L). [ABSTRACT FROM AUTHOR]

Laminaria japonica biomass was investigated as an untapped carbon source for polyhydroxyalkanoates (PHA) accumulation via batch and fed-batch cultivation of three different bacterial strains including Cupriavidus necator NCIMB 11599, Paracoccus sp. LL1, and Bacillus megaterium ALA2. Algal biomass (10% (w/v)) was treated with different sulfuric and hydrochloric acid concentrations (0.1, 0.15, 0.2, and 0.3 N). Increasing acid concentration led to a significant increase in reducing sugar production, giving rise to a maximum production of 6.1 and 5.9 g/L for H 2 SO 4 and HCl pretreatment, respectively. Shake flask culture revealed that C. necator , Paracoccus sp. LL1, and B. megaterium ALA2 were able to produce PHA up to 19–32% of their dry cell weight (DCW) under 2% of reducing sugar supplementation. Overall, C. necator showed the highest level of PHA accumulation (1.58 g/L, 32% of DCW). By batch and fed-batch culture, PHA content was enhanced to 44 and 49%, respectively. Along with PHA, Paracoccus sp. LL1 was able to produce 0.9 mg/L of carotenoids after 96 h of cultivation in flask culture. Carotenoid production was enhanced by batch and fed-batch culture to 1.45 and 2.3 mg/L, respectively. Based on Fourier transform infrared spectroscopy, gas chromatography, and 1H nuclear magnetic resonance spectroscopy, the produced PHA polymers were identified as poly(3-hydroxybutyrate) or poly(3-hydroxybutyrate- co -3-hydroxyvalerate). [ABSTRACT FROM AUTHOR]

• The wastewater of non-alcoholic beer-producing mill was used as an inexpensive carbon source for the culture medium. • The polyhydroxyalkanoates (PHAs) was produced by bacterium Cupriavidus necator. • A batch system was chosen for the fermentation process. • The ratio of C/N/P = 100:2:15 and the maltose concentration of 40 g L−1 were selected. Recent technologies have been directed toward the use ofinexpensive carbon sources like agricultural wastes and wastewaters in order to produce polyhydroxyalkanoates (PHAs) in a large commercial and industrial scaleand to reducehazardous pollutants. This study aimed toproduce poly-3-hydroxybutyrate (PHB) from wastewater of the beer brewery industry using Cupriavidus necator. For this purpose, the experiments were performed at three steps to evaluate the effect ofC/N and C/Pratiosand industrial-grade maltose on biopolymer production. The batch system was chosen for the fermentation process and the alteration of bacterial growth and NH 4 +-N and PO 4 3−-P consumption were monitored at24 h intervals.Maximum biopolymer productionof 1.98 g L−1and biomass yield of 0.45 g biomass/g consumed sugarwere obtained at the ratio of C/N/P = 100:2:15 and maltose concentration of 40 gL−1.Besides,the highest biopolymer yield and volumetric productivity associated with the ratio of C/N/P = 100:2:15 were 0.28 g g−1and 0.022 g L−1 h−1, respectively. Therefore,the C/N/P ratio of 100:2:15 and the maltose concentration of 40 gL−1were selected as the optimum condition which then generalized to the raw wastewater.The assessment of experimental data showed the amount of produced biomass and biopolymer in the raw wastewater as 7.9 and 3 g L−1, respectively. However, it can be concluded that the beer brewery wastewater has a high extraordinary potential for PHB production which could be an appropriate and eco-friendly alternative for petroleum-derived plastics. [ABSTRACT FROM AUTHOR]