Polyhydroxyalkanoate production from poly(ethylene furanoate) using a completely biotechnological approach.

Mixed bacterial cultures are increasingly being used in the production of polyhydroxyalkanoates (PHAs), as they have the potential to be more cost effective than axenic pure cultures. The purpose of this study was to use pure cultures in combination to identify their potential of PHA production. In this work we used volatile fatty acids (VFAs) and glucose as carbon source to check the ability of selected strains ST2 (Pseudomonas sp.) and CS8 (Bacillus sp.) as co-culture. The production of PHA in pure co-cultures of bacteria was therefore investigated in order to understand the effect of combining cultures on PHA production parameters and material properties. Bacteria could use the feed in better way when mixed as compared to individual strain. In undertaking this analysis, model volatile fatty acids (i.e., acetic and propionic acids) were used alone and in combination with glucose as feedstock. The production by Pseudomonas was 34% while 24% by Bacillus. However when combined and mixed feed (glucose + propionic acid) was used, 35% PHA produced. Overall, it was found that the ability of the pure cultures to produce PHA was low but when selected cultures were mixed, their ability to produce PHA was enhanced. Copolymers were obtained instead of homopolymers with improved properties. This suggests that industrial wastewater rich in volatile fatty acids and carbohydrates can be a good carbon source for PHA production with variable properties.

Plastic production and accumulation have devastating environmental effects, and consequently, the world is in need of environmentally friendly plastic substitutes. In this context, polyhydroxyalkanoates (PHAs) appear to be true alternatives to common plastics because they are biodegradable and biocompatible and can be biologically produced. Despite having comparable characteristics to common plastics, extensive PHA use is still hampered by its high production cost. PHAs are bacterial produced, and one of the major costs associated with their production derives from the carbon source used for bacterial fermentation. Thus, several industrial waste streams have been studied as candidate carbon sources for bacterial PHA production, including whey, an environmental contaminant by-product from the dairy industry. The use of whey for PHA production could transform PHA production into a less costly and more environmentally friendly process. However, the efficient use of whey as a carbon source for PHA production is still hindered by numerous issues, including whey pre-treatments and PHA producing strain choice. In this review, current knowledge on using whey for PHA production were summarized and new ways to overcome the challenges associated with this production process were proposed.

One-pot polyhydroxyalkanoate (PHA) production from Cerbera odollam (sea mango) oil using Pseudomonas resinovorans: Optimal fermentation design and mechanism.

Valorization of food waste derived anaerobic digestate into polyhydroxyalkanoate (PHA) using Thauera mechernichensis TL1

Conventional plastic products are made of crude oil components through polymerization. Aim of the project ANIMPOL is to convert lipids into polyhydroxyalkanoates (PHA) which constitute a group of biobased and biodegradable polyesters. Replacing fossil based plastics with biobased alternatives can help reducing dependence on crude oil and decrease greenhouse gas emissions. As substrate material waste streams from slaughtering cattle, pig or poultry are taken into account. Lipids from rendering site are used for biodiesel production. Slaughtering waste streams may also be hydrolyzed to achieve higher lipid yield. Biodiesel can be separated into a high and low quality fraction. High quality meets requirements for market sale as fuel and low quality can be used for PHA production. This provides the carbon source for PHA production. Nitrogen source for bacteria reproduction is available from hydrolyzed waste streams or can be added separately. Selected microbial strains are used to produce PHA from this substrate. An optimized process design will minimize waste streams and energy losses through recycling. Ecological evaluation of the process design will be done through footprint calculation according to Sustainable Process Index methodology (Sandholzer et. al, 2005; Narodoslawsky and Krotscheck, 1995).

Synthetic plastics are in great demand in society due to their diversified properties, but they cause environmental pollution due to their non-biodegradable nature. Therefore, synthetic plastics are in need to be replaced with biodegradable plastics. Polyhydroxyalkanoates (PHAs), bacterial biopolymers are natural alternative to synthetic plastics. These are present inside the bacterial cytoplasm in granular form. Presently, the production cost of PHA is high due to expensive carbon substrates used in its biosynthesis. Therefore, this study focuses on the cost-effective production of PHA using waste carbon sources. Rice bran and sugarcane molasses were used as the carbon source for PHA production from Bacillus subtilis, Bacillus cereus, Alcaligenes sp. and Pseudomonas aeruginosa. PHA production from these bacterial strains was confirmed through Sudan Black-B screening. With rice bran, as carbon source, the highest PHA yield obtained was for P. aeruginosa, which yielded 93.7% and lowest was 35.5% for B. cereus. Surprisingly, B. cereus produced the highest cell dry mass (0.045 g/L) but its extracted PHA contents were lowest being only 0.02 g/L. Alcaligenes sp. with 0.031 g/L CDM yielded 87.1% PHA. B. subtilis had a CDM 0.029 g/L, 0.02 g/L PHA content and a yield of 69.10%. In the case of sugarcane molasses, P. aeruginosa produced 95% PHA yield, 0.02 g/L CDM, and 0.019 g/L PHA content. Alcaligenes sp. yielded 90.9% PHA, 0.011 g/L CDM, and 0.01 g/L PHA content. B. subtilis produced 91.6% PHA yield, 0.012 g/L CDM, 0.011 g/L PHA content; B. cereus produced 80% PHA yield, 0.015 g/L CDM, 0.012 g/L PHA content at 37°C, pH 7. Higher concentrations of carbon sources increased the CDM and decreased the PHA yield. The maximum yield of PHA was obtained from sugarcane molasses. 24-48 h of incubation was optimal for B. subtilis and B. cereus, while for Alcaligenes and P. aeruginosa incubation time of 48-96 h was desirable for higher PHA yield. The extracted biopolymers were analyzed by Fourier transform infrared spectroscopy (FTIR), which identified the extracted biopolymers as poly-3-hydroxybutyrate P(3HB). The thermal properties of the extracted biopolymers, such as melting temperatures, were analyzed by differential scanning calorimetry (DSC), which confirmed the thermal stability.

Process optimization for polyhydroxyalkanoate (PHA) production from waste via microbial enrichment cultures

Polyhydroxyalkanoates (PHAs) are biodegradable polymers that otherwise exhibit many properties similar to that of conventional, non-biodegradable plastics. Hence, they are considered as potential substitutes for non-biodegradable plastics. But industrial production and commercialization of PHA have been hindered greatly due to the high cost requirements, especially those involved in the provision of suitable carbon sources. In this study, sugarcane molasses was used as a cheap carbon source for PHA production using a wild strain of Enterobacter cloacae isolated from sugarcane extract. This isolate was selected for PHA production based on Sudan Black B staining, and it was subsequently identified by performing BLASTn using its 16S rRNA sequence (GenBank accession number: ON314993). The PHA yield was studied under varying conditions of initial pH, molasses concentration and inoculum concentration. The highest yield of 4.13 - 4.98 g/L or 48 - 56% PHA was obtained after 48-60 h incubation at initial pH 7, molasses concentration 4% and inoculum concentration 2%. After downstream processing, the extracted PHA was characterized by FTIR spectroscopy. It is concluded that E. cloacae has the potential to utilize sugarcane molasses as a cheap carbon source to yield impressive amounts of PHA, and that it should be considered a candidate for further studies and for the cheaper industrial production of PHA.

The sustainable high-capacity production of the biodegradable biopolymer polyhydroxyalkanoate (PHA) requires the availability of large amounts of carbon-neutral carbonaceous substrates. Harnessing organic waste, such as municipal solid and agricultural waste, sewage sludge, and biomass, for bioconversion to bioplastics, presents a cost-efficient opportunity. Nevertheless, these carbon sources present a large diversity in terms of composition and, therefore, would lead to inconsistent polymer quality. The preliminary transformation of such waste streams by gasification into syngas leads to a more defined gaseous substrate consisting primarily of CO, H2, CO2, and CH4. The components of this gas mix can serve as substrates in so-called syngas fermentation. A few types of bacteria can assimilate CO as carbon and/or an energy source. This includes acetogens, which use CO and CO2 as carbon and energy sources to produce acetyl-CoA and finally acetate in the Wood–Ljungdahl pathway. These bacteria do not possess the enzymes for the production of PHA in their wild-type form, but this hurdle has been overcome recently by genetic engineering. Carboxydobacteria can grow solely on CO in aerobic conditions and can produce PHA. Their growth rate may, however, vary as a function of the CO concentration in the gas mixture. CO-tolerant hydrogen-oxidizing bacteria can grow in syngas on CO2 and H2, in aerobic conditions at low CO concentration, but de facto cannot assimilate CO. They can accumulate high PHA content. Finally, Rhodospirillum rubrum is the most studied bacterial species for the conversion of syngas to PHA but exhibits only a modest growth rate and limited PHA accumulation capacity. Genetic engineering of these bacteria was also investigated and may lead to higher PHA production rates. The underlying processes of waste and biomass gasification and gas fermentation will be discussed in detail in this chapter, together with the metabolic pathways involved in the assimilation of syngas as carbon and energy sources.

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 H2SO4, 120 min and 90 ºC. The ability of Cupriavidus necator to grow on CP hydrolysate and produce PHA was screened resulting in up to OD600 15.8 and 1.5 g/L of PHA (31% (gPHA/gDCW)). 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.

Poly(ethylene terephthalate) (PET) is a common single-use plastic and a major contributor to plastic waste. PET upcycling through enzymatic depolymerization has drawn significant interests, but lack of robust enzymes in acidic environments remains a challenge. This study investigates in-situ product removal (ISPR) of protons and monomers from enzymatic PET depolymerization via a membrane reactor, focusing on the ICCG variant of leaf branch compost cutinase. More than two-fold improvements in overall PET depolymerization and terephthalic acid yields were achieved employing ISPR for an initial PET loading of 10 mgPET mlbuffer -1. The benefit of ISPR was reduced for a lower initial loading of 1 mgPET mlbuffer -1 due to decreased need for pH stabilization of the enzyme-containing solutions. A back-of-envelop analysis suggests that at a modest dilution ratio, ISPR could help achieve savings on caustic base solutions used for pH control in a bioreactor. Our study provides valuable insights for future ISPR developments for enzymatic PET depolymerization, addressing the pressing need for more sustainable solutions towards plastic recycling and environmental conservation.

Polyhydroxyalkanoates (PHAs) are biodegradable polyesters with comparable properties to some petroleum-based polyolefins. PHA production can be achieved in open, mixed microbial cultures and thereby coupled to wastewater and solid residual treatment. In this context, waste organic matter is utilised as a carbon source in activated sludge biological treatment for biopolymer synthesis. Within the EU project Routes, the feasibility of PHA production has been evaluated in processes for sludge treatment and volatile fatty acid (VFA) production and municipal wastewater treatment. This PHA production process is being investigated in four units: (i) wastewater treatment with enrichment and production of a functional biomass sustaining PHA storage capacity, (ii) acidogenic fermentation of sludge for VFA production, (iii) PHA accumulation from VFA-rich streams, and (iv) PHA recovery and characterisation. Laboratory- and pilot-scale studies demonstrated the feasibility of municipal wastewater and solid waste treatment alongside production of PHA-rich biomass. The PHA storage capacity of biomass selected under feast-famine with municipal wastewater has been increased up to 34% (g PHA g VSS(-1)) in batch accumulations with acetate during 20 h. VFAs obtained from waste activated sludge fermentation were found to be a suitable feedstock for PHA production.

Polyhydroxyalkanoates (PHA) production from phenol in an acclimated consortium: Batch study and impacts of operational conditions

Realizing a sustainable development of our planet requires a reduction of waste production, harmful emissions, and higher energy efficiency as well as utilization of renewable energy sources. One pathway to this end is the design of sustainable biorefinery concepts. Utilizing waste streams as raw material is gaining great importance in this respect. This reduces environmental burden and may at the same time contribute to economic performance of biorefineries. This paper investigates the utilization of slaughtering waste to produce biodegradable polyesters, polyhydroxyalkanoates (PHA), via bioconversion. PHA are the target product while production of high quality biodiesel along with meat and bone meal (MBM) as by-products improves the economic performance of the process. The paper focuses on ecological comparison of different production scenarios and the effect of geographical location of production plants taking different energy production technologies and resources into account; ecological footprint evaluation using Sustainable Process Index methodology was applied. Keeping in mind that the carbon source for PHA production is produced from waste by energy intensive rendering process, the effect of available energy mixes in different countries becomes significant. Ecological footprint results from the current study show a bandwidth from 372,950 to 956,060 m2/t PHA production, depending on the energy mix used in the process which is compared to 2,508,409 m2/t for low density polyethylene.

Use of bacteriostatic antibiotics for the optimization of new media in view of supplementing POME as an alternative carbon source for PHA production - a statistical approach