Feedstock For Polyhydroxyalkanoate Production Research Articles

Production of poly(3-hydroxybutyrate)/poly(lactic acid) from industrial wastewater by wild-type Cupriavidus necator H16

The massive production of urban and industrial wastes has created a clear need for alternative waste management processes. One of the more promising strategies is to use waste as raw material for the production of biopolymers such as polyhydroxyalkanoates (PHAs). In this work, a lactate-enriched stream obtained by anaerobic digestion (AD) of wastewater (WW) from a candy production plant was used as a feedstock for PHA production in wild-type Cupriavidus necator H16. Unexpectedly, we observed the accumulation of poly(3-hydroxybutyrate)/poly(lactic acid) (P(3HB)/PLA), suggesting that the non-engineered strain already possesses the metabolic potential to produce these polymers of interest. The systematic study of factors, such as incubation time, nitrogen and lactate concentration, influencing the synthesis of P(3HB)/PLA allowed the production of a panel of polymers in a resting cell system with tailored lactic acid (LA) content according to the GC–MS of the biomass. Further biomass extraction suggested the presence of methanol soluble low molecular weight molecules containing LA, while 1 % LA could be detected in the purified polymer fraction. These results suggested that the cells are producing a blend of polymers. A proteomic analysis of C. necator resting cells under P(3HB)/PLA production conditions provides new insights into the latent pathways involved in this process. This study is a proof of concept demonstrating that LA can polymerize in a non-modified organism and paves the way for new metabolic engineering approaches for lactic acid polymer production in the model bacterium C. necator H16.

Microalgae in Bioplastic Production: A Comprehensive Review.

The current era of industrialization includes a constantly increasing demand for plastic products, but because plastics are rarely recycled and are not biodegradable plastic pollution or "white pollution" has been the result. The consumption of petroleum-based plastics will be 20% of global annual oil by 2050, and thus there is an inevitable need to find an innovative solution to reduce plastic pollution. The biodegradable and environmentally benign bioplastics are suitable alternative to fossil-based plastics in the market due to sustainability, less carbon footprint, lower toxicity and high degradability rate. Microalgal species is an innovative approach to be explored and improved for bioplastic production. Microalgae are generally present in abundant quantity in our ecosystem, and polysaccharide in the algae can be processed and utilized to make biopolymers. Also, these species have a high growth rate and can be easily cultivated in wastewater streams. The review aims to determine the recent status of bioplastic production techniques from microalgal species and also reveal optimization opportunities involved in the process. Several strategies for bioplastic production from algal biomass are being discussed nowadays, and the most prominent are "with blending" (blending of algal biomass with bioplastics and starch) and "without blending" (microalgae as a feedstock for polyhydroxyalkanoates production). The advanced research on modern bioengineering techniques and well-established genetic tools like CRISPR-Cas9 should be encouraged to develop recombinant microalgae strains with elevated levels of PHA/PHB inside the cell.

Optimum Condition for Polyhydroxyalkanoate Production from Crude Glycerol by Bacillus sp. Isolated from Lipid-Containing Wastewater

Polyhydroxyalkanoates (PHAs) are a group of biopolymers used as an alternative to petroleum-based synthetic plastics. Their industrial application is not widely available due to production cost constraints, mainly from raw materials used for carbon sources. This research focuses on selecting a Bacillus strain from lipid-containing wastewater that can produce PHAs from crude glycerol and investigating the optimum conditions for producing PHAs from crude glycerol. The Bacillus strain was isolated from the wastewater storage pond at a fermented pork sausage manufacturing plant in Thailand for PHAs production utilizing Mineral Salt Medium (MSM) with 1 % w/v glucose as a carbon source. PHAs synthesis was preliminarily investigated by staining cells with Sudan Black B. The isolated FMI3 produced the highest PHAs at 43 % of the dry cell weight (DCW). It was identified as Bacillus pumilus FMI3. Crude glycerol was obtained from a by-product of the transesterification of waste cooking oil catalysed by NaOH. It was partially purified by acidification and neutralization and exhibited about 80 % w/w glycerol, 1.90 ± 0.09 % ash content, 2.80 ± 0.14 % water content, light brown colour, and pH 7.11 ± 0.35. Isolated B. pumilus FMI3 grows best and produces the highest PHAs yields under optimum conditions, i.e., MSM containing crude glycerol and ammonium sulphate at 61:1 mole ratio as carbon and nitrogen sources respectively, 15 % inoculum, initial pH of neutral at 7, and shaking at 150 rpm at 40 °C for 72 h. These conditions achieved PHAs at 79 % of DCW, classified as medium-chain-length PHAs comprising 3-hydroxyoctanoate,3-hydroxydecanoate, 3-hydroxydodecanoate, and 3-hydroxytetradecanoate at 9, 12, 67 and 12 %, respectively. This study reported the feasibility of utilizing crude glycerol as feedstock for PHAs production by the B. pumilus FMI3 strain, which was able to grow on and tolerate salts of crude glycerol. HIGHLIGHTS Bacteria which endure extreme environments (i.e., very limited of nutrients; drought and chemicals) can produce polyhydroxyalkanoates from crude glycerol Polyhydroxyalkanoates production from partially purified crude glycerol is presented The yield of polyhydroxyalkanoates achieve at 79 % of dry cell weight under the optimum condition GRAPHICAL ABSTRACT

Waste as feedstock for polyhydroxyalkanoate production from activated sludge: Implications of aerobic dynamic feeding and acidogenic fermentation

Polyhydroxyalkanoates (PHA) are the ideal substitute for petroleum-derived non-biodegradable plastics. However, the cost of polymer production restricts the large-scale implementation. Waste feedstocks are a perfect carbon source to balance the cost and waste disposal and minimization. The suitability of activated sludge as inoculum for PHA production from potential waste feedstocks was analyzed for an affordable production strategy through waste management in a three-step methodology. The methodology involves a combined acidogenic fermentation and aerobic dynamic feeding strategy to improve PHA accumulation. Firstly, the specificity of waste feedstock for storage response was increased through volatile fatty acid (VFAs) production by tuning the process elements during acidogenic fermentation depending on the type of substrate. Secondly, activated sludge enriched through aerobic dynamic feeding strategy for improved storage response weeds out non-accumulators through various approaches. Finally, PHA accumulation bulks the enriched mix culture with PHA through different routes to enable economic downstream processing. The acidogenic fermentation critically impacts PHA composition and property along with operating conditions during the process. These studies point towards the feasibility of integrating PHA production by three-step methodology to the existing waste treatment facility and its future scope. Further investigations to improve the efficiency of the process and polymer properties can lead to cheaper polymer production more comprehensive market application.

Lignocellulosic biomass (LCB): a potential alternative biorefinery feedstock for polyhydroxyalkanoates production

Polyhydroxyalkanoates (PHAs) are one of the most promising, degradable and eco-friendly alternatives to fossil fuel-based plastic. Nevertheless, PHA derived from edible sources is a relatively easier process than using other resources. Cost of raw material is being considered as a significant constraint for sustainability of industrial bioplastic production. In recent days, lignocellulosic biomass (LCB) in the form of waste residue generated from agriculture, forestry, energy crop system, marine biomass, industrial and municipal solid waste has gained great attention as it is the most abundant feedstock worldwide and supports the sustainable production of PHA. However, the conversion efficiency and PHA yield vary significantly based on the source and nature of LCB due to their content distinction. The complex structure of LCB, mainly composed of cellulose, hemicellulose, and lignin, makes it challenging to be depolymerized. Therefore, the processes required to utilize LCB for production of PHA are covered in this review including pretreatment, hydrolysis, fermentation, and the associated difficulties during the process development. In addition, several attempts made to exploit LCB as a feedstock for PHA production were also discussed in order to improve the overall conversion process.

Syngas obtained by microwave pyrolysis of household wastes as feedstock for polyhydroxyalkanoate production in Rhodospirillum rubrum.

SummaryThe massive production of urban and agricultural wastes has promoted a clear need for alternative processes of disposal and waste management. The potential use of municipal solid wastes (MSW) as feedstock for the production of polyhydroxyalkanoates (PHA) by a process known as syngas fermentation is considered herein as an attractive bio‐economic strategy to reduce these wastes. In this work, we have evaluated the potential of Rhodospirillum rubrum as microbial cell factory for the synthesis of PHA from syngas produced by microwave pyrolysis of the MSW organic fraction from a European city (Seville). Growth rate, uptake rate, biomass yield and PHA production from syngas in R. rubrum have been analysed. The results revealed the strong robustness of this syngas fermentation where the purity of the syngas is not a critical constraint for PHA production. Microwave‐induced pyrolysis is a tangible alternative to standard pyrolysis, because it can reduce cost in terms of energy and time as well as increase syngas production, providing a satisfactory PHA yield.

Optimization of polyhydroxyalkanoate storage using mixed cultures and brewery wastewater

BACKGROUND Brewery wastewater is a potential feedstock for polyhydroxyalkanoates (PHA) production since it contains high concentrations of easily biodegradable organic matter. Activated sludge was submitted to aerobic dynamic feeding conditions in a sequencing batch reactor fed fermented brewery wastewater in order to select a microbial culture with high storage capacity. The effect of several operational parameters, such as substrate concentration (57, 79 and 109 Cmmol L−1), pH (7 and 9 and without pH control (8–9)) and temperature (15 and 30 °C and without T control (15–28 °C)) was investigated. RESULTS The concentration of PHA stored by the activated sludge increased with the substrate concentration, with 39% PHA content on a dry biomass basis obtained at 109 Cmmol L−1. The storage yield increased from 0.35 to 0.43 Cmmol HA Cmmol−1 VFA when the substrate concentration was raised from 57 to 79 Cmmol L−1. However, a further increase in substrate concentration to 109 Cmmol L−1 led to a storage yield decrease to 0.39 Cmmol HA Cmmol−1 VFA. Control of pH and temperature did not enhance PHA storage. CONCLUSIONS Brewery wastewater is a good feedstock for production of PHAs using mixed cultures enriched under feast and famine conditions. PHA production can be enhanced by manipulating the operational conditions. © 2016 Society of Chemical Industry

Long-term cultivation of a stable Methylocystis-dominated methanotrophic enrichment enabling tailored production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Methane (CH4) is a readily available feedstock for production of polyhydroxyalkanoates (PHAs). The structure and PHA production capacity of a Methylocystis-dominated methanotrophic enrichment was stable in long-term operation (>175days) when grown exponentially under non-aseptic conditions in fill-and-draw batch cultures with ammonium as nitrogen source. Cells harvested in the draw step were incubated in the absence of nitrogen with various combinations of CH4 and valerate to assess capacity for synthesis of poly(3-hydroxybutyrate) (P3HB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). When fed CH4 alone, only P3HB was produced. When fed CH4 plus valerate, PHBV was synthesized. The mol% of 3-hydroxyvalerate (3HV) increased with added valerate. Oxidation of CH4 was required for valerate assimilation, and the fraction of CH4 oxidized increased with increased mol% 3HV. By separating PHA accumulation from cell replication, tailored PHA-rich biomass can be generated by addition of co-substrate, while retaining a large inoculum for the next cycle of cell division.

Crude glycerol as feedstock for polyhydroxyalkanoates production by mixed microbial cultures

The increase in global biodiesel production makes imperative the development of sustainable processes for the use of its main by-product, crude glycerol. In this study the feasibility of polyhydroxyalkanoates (PHA) production by a mixed microbial community using crude glycerol as feedstock was investigated. The selected culture had the ability to consume both glycerol and methanol fraction present in the crude. However, glycerol seemed to be the only carbon source contributing for the two biopolymers stored: poly-3-hydroxybutyrate (PHB) and glucose biopolymer (GB). In this work the culture reached a maximum PHB content of 47% (cdw) and a productivity of 0.27 g X/L.d, with an aerobic mixed cultures and a real waste substrate with non-volatile fatty acids (VFA) organic matter. The overall PHA yield on total substrate obtained was in the middle range of those reported in literature. The fact that crude glycerol can be used to produce PHA without any pre-treatment step, makes the overall production process economically more competitive, reducing polymer final cost.