Maximum Polyhydroxyalkanoates Research Articles

Synergistic effects of peracetic acid and free ammonia pretreatment on anaerobic fermentation of waste activated sludge to promote short-chain fatty acid production for polyhydroxyalkanoate biosynthesis: Mechanisms and optimization

Peracetic acid (PAA) combined with free ammonia (FA) pretreatment can be utilized to promote anaerobic fermentation (AF) of waste activated sludge (WAS) to produce short-chain fatty acids (SCFAs), and the resulting SCFAs are desirable carbon sources (C-sources) for polyhydroxyalkanoate (PHA) biosynthesis. This work aimed to determine the optimum conditions for PAA + FA pretreatment of sludge AF and the feasibility of using anaerobic fermentation liquor (AFL) for PHA production. To reveal the mechanisms of integrated pretreatment, the impacts of PAA + FA pretreatment on different stages of sludge AF and changes in the microbial community structure were explored. The experimental results showed that the maximum SCFA yield reached 491.35 ± 6.02 mg COD/g VSS on day 5 after pretreatment with 0.1 g PAA/g VSS +70 mg FA/L, which was significantly greater than that resulting from PAA or FA pretreatment alone. The mechanism analysis showed that PAA + FA pretreatment promoted sludge solubilization but strongly inhibited methanogenesis. According to the analysis of the microbial community, PAA + FA pretreatment changed the microbial community structure and promoted the enrichment of bacteria related to hydrolysis and acidification, and Proteiniclasticum, Macellibacteroides and Petrimonas became the dominant hydrolytic and acidifying bacteria. Finally, after alkali treatment, the AFL was utilized for batch-mode PHA production, and a maximum PHA yield of 55.05 wt% was achieved after five operation periods.

Evaluation of polyhydroxyalkanoate recovery from food waste by sequencing batch biofilm reactor with high mixed microbial biomass

In this study, the enrichment sequencing batch biofilm reactor (SBBR) and conventional enrichment reactor (SBR) were established, and a new strategy was developed to achieve higher biomass yield and polyhydroxyalkanoate (PHA) production from food waste than those achieved through the conventional method. After the 10th day of an expanded cultivation period, the respective active biomass concentrations in SBR and SBBR were 5.16 and 13.92 g/L, indicating a significant improvement in the biomass yield of mixed microbial culture in the SBBR. The PHA accumulation test revealed that maximum PHA concentration in SBR and SBBR reached 6.60 and 12.70 g/L, respectively, after 80 days of enrichment, indicating that compared to SBR, the SBBR could more effectively improve the PHA accumulation capacity. Meganema, Thauera, and Paracoccus were the dominant PHA-accumulating bacteria in the SBR and SBBR. Additionally, the volumetric productivity of the SBBR was 3.22 g COD/L/d, twice that of the SBR. This study provides new strategies and insights for improving PHA production and reducing the costs of PHA production and reactor investment.

Enrichment performance and salt tolerance of polyhydroxyalkanoates (PHAs) producing mixed cultures under different saline environments

The key to the resource recycling of saline wastes in form of polyhydroxyalkanoates (PHA) is to enrich mixed cultures with salt tolerance and PHA synthesis ability. However, the comparison of saline sludge from different sources and the salt tolerance mechanisms of salt-tolerant PHA producers need to be clarified. In this study, three kinds of activated sludge from different salinity environments were selected as the inoculum to enrich salt-tolerant PHA producers under aerobic dynamic feeding (ADF) mode with butyric acid dominated mixed volatile fatty acid as the substrate. The maximum PHA content (PHAm) reached 0.62 ± 0.01, 0.62 ± 0.02, and 0.55 ± 0.03 g PHA/g VSS at salinity of 0.5%, 0.8%, and 1.8%, respectively. Microbial community analysis indicated that Thauera, Paracoccus, and Prosthecobacter were dominant salt-tolerant PHA producers at low salinity, Thauera, NS9_marine, and SM1A02 were dominant salt-tolerant PHA producers at high salinity. High salinity and ADF mode had synergistic effects on selection and enrichment of salt-tolerant PHA producers. Combined correlation network with redundancy analysis indicated that trehalose synthesis genes and betaine related genes had positive correlation with PHAm, while extracellular polymeric substances (EPS) content had negative correlation with PHAm. The compatible solutes accumulation and EPS secretion were the main salt tolerance mechanisms of the PHA producers. Therefore, adding compatible solutes is an effective strategy to improve PHA synthesis in saline environment.

Investigating the efficiency of a two-stage anaerobic-aerobic process for the treatment of confectionery industry wastewaters with simultaneous production of biohydrogen and polyhydroxyalkanoates.

The scope of the current study was to investigate the efficiency of a two-stage anaerobic-aerobic process for the simultaneous treatment and valorization of selective wastewater streams from a confectionary industry. The specific wastewater (confectionary industry wastewater, CIW) was a mixture of the rinsing eluting during washing of the cauldrons in which jellies and syrups were produced, and contained mainly readily fermentable sugars, being thus of high organic load. The first stage of the process was the dark fermentation (DF) of the CIW in continuous, attached-biomass systems, in which the effect on hydrogen yields and distribution of metabolites were studied for different packing materials (ceramic or plastic), hydraulic retention times, HRTs (12 h–30 h) and feed substrate concentration (20 g COD/L- 50 g COD/L). In the second stage, the effectiveness of the aerobic treatment of the DF effluents was evaluated in terms of the reduction of the organic load and the production of polyhydroxyalkanoates (PHAs) through an enriched mixed microbial culture (MMC). The MMC was developed in a continuous draw and fill system, in which the accumulation potential of PHAs was studied. It was shown that the hydrogen production rates decreased for increasing substrate concentration and HRTs, with a maximum of 12.70 ± 0.35 m3 H2/m3 initial CIW achieved for the lowest HRT and feed concentration and using ceramic beads as packing material. Butyrate, acetate and lactate were the main metabolites generated in all cases, in different ratios. The distribution of metabolites during DF was shown to highly affect the efficiency of the second process in terms of both the reduction of organic load and the PHAs yields. The highest removal of organic load achieved after 48 h of aerobic treatment was 84.0 ± 0.9 %, whereas the maximum PHAs yield was 21.46 ± 0.13 kg PHAs/m3 initial CIW.

Spatial separation of nitrifiers and denitrifiers promotes selection and enrichment of polyhydroxyalkanoates storing mixed cultures fed by crude glycerol and propionate wastewater

Polyhydroxyalkanoates (PHA) recovery from industrial wastewater has been highlighted as a promising strategy for a circular bioeconomy. However, the high and varying level of nitrogen in wastewater makes enrichment of mixed microbial culture (MMC) low efficiency. In this study, spatial separation of nitrifiers and denitrifiers was adopted by adding biocarriers in MMC and decreasing the sludge retention time (SRT) to accelerate the enrichment of PHA-storing MMC fed by mixed wastewater containing glycerol and propionate. Nitrifiers and denitrifiers were sustained on biocarriers, obtaining a high total inorganic nitrogen removal and allowing a more efficient selective pressure of a high carbon and nitrogen ratio (C/N) under low SRT conditions. The maximum PHA cell content and relative abundance of PHA-storing bacteria were increased to 60.51 % (SRT 6 d) and 49.62 % (SRT 6 d) with the decrease of SRT, respectively. This study demonstrates an efficient way to highly enrich PHA-storing MMC from crude glycerol, which provide a relevant technical support for high-efficiency enrichment of PHA-storing bacteria in low C/N wastewater.

Bioconversion of glycerol into polyhydroxyalkanoates through an atypical metabolism shift using Priestia megaterium during fermentation processes: A statistical analysis of carbon and nitrogen source concentrations

Polyhydroxyalkanoates (PHA) are bioplastics which are well known as intracellular energy storage compounds and are produced in a large number of prokaryotic species. These bio-based inclusions are biodegradable, biocompatible and environmental friendly. Industrial production of, short chain and medium chain length PHA, involves the use of microorganisms and their enzymes. Priestia megaterium previously known as Bacillus megaterium is a well-recognized bacterium for producing short chain length PHA. This study focuses to characterize this bacterium for the production of medium chain length PHA, and a novel blend of both types of monomers having enhanced properties and versatile applications. Statistical analyses and simulations were used to demonstrate that cell dry weight can be derived as a function of OD600 and PHA content. Optimization of growth conditions resulted in the maximum PHA production as: 0. 05 g. g-x. H−1, where the rate of PHA production was 0.28 g L−1. H−1 and PHA concentration was 4.94 g. L−1. This study also demonstrated FTIR to be a semi quantitative tool for PHA production. Moreover, conversion of scl-PHA to mcl-PHA with reference to time intermissions using GC-FID are shown.

Simultaneous treatment of epichlorohydrin wastewater and polyhydroxyalkanoate recovery by halophilic aerobic granular sludge highly enriched by Halomonas sp.

The treatment of epichlorohydrin (ECH) wastewater exists chances for achieving cleaner production. This study initially employed moderately halophilic aerobic granular sludge (HAGS) to treat ECH wastewater, and the resulting HAGS was utilized to recover polyhydroxyalkanoate (PHA). During the acclimation process of HAGS, the chemical oxygen demand removal efficiency stabilized at 70 %. Moreover, due to the high enrichment of Halomonas sp. (relative abundance of 86 ± 0.50 %), the maximum PHA content of wasted HAGS was 52.67 wt% in the fermentation process. Simultaneously, the utilization of nuclear magnetic resonance spectroscopy (1H and 13C spectra) and fourier transform infrared spectroscopy for the structural analysis of polymers revealed that polyhydroxybutyrate was the predominant substance extracted from HAGS. In this study, the innovative use of highly enriched HAGS for treating ECH wastewater and simultaneously recovering PHA not only enables the efficient biological treatment of ECH wastewater but also realizes resource recovery of ECH wastewater.

Biosynthesis of polyhydroxyalkanoates (PHAs) from non-edible Cerbera odollam (sea mango) oil

Polyhydroxyalkanoates (PHAs) are biodegradable polymers, which have recently attracted much attention as a promising substitute for petroleum-based plastics. For circumventing the financial barrier of PHA production, non-edible Cerbera odollam oil was proposed as a novel PHA feedstock. The objective of this study was to investigate the feasibility of C. odollam oil for PHA production using Cupriavidus necator and Pseudomonas resinovorans. The PHA production performance of P. resinovorans on different oil conditions (i.e., crude, hydrolyzed, and emulsified oil) was also compared. Direct fermentation of crude C. odollam oil by P. resinovorans showed the most promising results with a biomass accumulation of 1.32 g/L and a maximum PHA concentration of 0.25 g/L (corresponding to 18.8 % polymer content). The polymer was composed of 3-hydroxybutyrate (3HB), 3-hydroxyhexanoate (3HHx), 3-hydroxyoctanoate (3HO), and 3-hydroxydecanoate (3HD). For the first time, C. odollam oil has been proven to be a feasible feedstock for an economical production of PHAs.

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

Polyhydroxyalkanoate (PHA) is a biopolymer that can be used as a bioplastic, offering a green alternative to petroleum-based plastics. In this study, we investigated PHA production using Thauera mechernichensis TL1. The optimal molar C/N ratio was determined to be 20 from among the ratios of 4, 20, 40, 80, and 200 and in the absence of nitrogen. Food waste anaerobic digestate, mainly comprised of acetate and propionate, was used as the carbon source for PHA production by T. mechernichensis TL1, resulting in a maximum PHA content of 23.98 ± 0.52 wt% (0.52 ± 0.02 g/L PHA) with a PHA productivity of 0.043 g/L-h PHA. In addition, when using acetate and propionate, T. mechernichensis TL1 produced PHA with a maximum PHA content of 57.43 ± 2.84 wt% (2.04 ± 0.11 g/L PHA) and 50.94 ± 1.61 wt% (2.62 ± 0.16 g/L PHA), with a PHA productivity of 0.092 g/L-h PHA and 0.070 g/L-h PHA, respectively. Proton nuclear magnetic resonance spectroscopy (1H NMR) confirmed polyhydroxybutyrate (PHB) production using acetate as a carbon source, and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) production using propionate or food waste anaerobic digestate as the carbon source. The whole-genome analysis of T. mechernichensis TL1 confirmed the existence of a PHA biosynthesis pathway, with the presence of phaA, phaB, phaC (Class I and Class II), and phaJ genes. This study was the first to demonstrate Thauera sp.’s ability to produce PHA from food waste anaerobic digestate, rendering it as a promising candidate for PHA-producing bacteria for the valorization of food waste.

Production of polyhydroxyalkanoates from hydrolysed rapeseed meal by Haloferax mediterranei

Rapeseed meal (RSM) hydrolysate is a potential low-cost feedstock for the production of polyhydroxyalkanoates (PHAs) by the archaea, Haloferax mediterranei. Acidic and enzymatic hydrolysis were carried out to compare effectiveness. Enzymatic hydrolysis is more effective than acidic hydrolysis for fermentation substrate leading to increased PHA productivity. H. mediterranei didn’t grow or produce PHA when acid hydrolysed RSM medium was present in proportions greater than 25% (vol.), potentially due to the effect of inhibitors such as furfural, hydroxymethylfurfural (HMF), etc. However, H. mediterranei was able to grow and produce PHA when using enzymatically hydrolysed RSM medium. The maximum PHA concentration of 0.512 g/L was found at 75% (vol.) in enzymatic RSM hydrolysate medium. The biopolymer obtained had improved thermal and mechanical properties compared to PHB homopolymer. RSM’s potential as a low-cost alternative feedstock for improved PHA production under non-sterile conditions was successfully demonstrated, and its usage should be further explored.

Polyhydroxyalkanoates production by an advanced food-on-demand strategy: The effect of operational conditions

Despite the increasing number of studies related to the polyhydroxyalkanoate (PHA) production from sewage sludge of wastewater treatment plants, there is still a gap in the correlation between the operational conditions, such as the organic loading rate (OLR), and the intracellular polyhydroxyalkanoate (PHA) content, productivity and final recovery of the polymer. Therefore, this work aims to provide experimental data on PHA productivity and purity in view of scaling up the process to an industrial level taking into account process parameters. In view of that, three OLR were applied during the selection of PHA-accumulating bacteria in sewage sludge. Then, the biomass was harvested and subjected to batch accumulation experiments at two organic loads per dosage by employing a tailor-made software to adopt an automated feed-on-demand strategy, which allowed for 30–56 h of accumulation tests in stand-alone mode. Finally, an improved protocol for PHA extraction has been applied. Experimental results show that the maximum PHA content (60% w/w) was achieved using the highest organic load per dosage during the accumulation test with the biomass selected at the highest OLR (1.8 g COD L−1 d−1). Also, the extraction protocol efficiency was proven with four samples with different PHA content, achieving recovery yield as high as 78 ± 3 % with a purity of 89 ± 2 %, thus demonstrating that the adopted strategy might be beneficial for industrial use.

Polyhydroxyalkanoate biosynthesis and optimisation of thermophilic Geobacillus stearothermophilus strain K4E3_SPR_NPP.

Polyhydroxyalkanoates (PHA) can be used to combat the challenges associated with plastic because it is biodegradable and can be produced from renewable resources. Extremophiles are considered to be potential PHA producers. An initial screening for the PHA synthesizing ability of a thermophilic bacteria Geobacillus stearothermophilus strain K4E3_SPR_NPP was carried out using Sudan black B staining. Nile red viable colony staining was used to further verify that the isolates produced PHA. Crotonic acid assays were used to determine the concentrations of PHA. The bacteria showed 31% PHA accumulation per dry cell weight (PHA/DCW) when glucose was used as a carbon source for growth. The molecule was identified to be medium chain length PHA, A copolymer of PHA containing poly(3-hydroxybutyrate)-poly(3-hydroxyvalerate)-poly(3-hydroxyhexanoate) (PHB-PHV-PHHX) using 1H-NMR. Six carbon sources and four nitrogen sources were screened for the synthesis of maximum PHA content, of which lactose and ammonium nitrate showed45% and 53% PHA/DCW respectively. The important factors in the experiment are identified using the Plackett-Burman design, and optimization is performed using the response surface method. Response surface methodology was used to optimize the three important factors, and the maximum biomass and PHA productions were discovered. Optimal concentrations yielded a maximum of 0.48g/l biomass and 0.32g/l PHA, measuring 66.66% PHA accumulation. Dairy industry effluent was employed for the synthesis of PHA, yielding 0.73g/l biomass and 0.33g/l PHA, measuring 45% PHA accumulation. These findings add credibility to the possibility of adopting thermophilic isolates for PHA production using low-cost substrates.

Exploiting Cheese Whey for Efficient Selection of Polyhydroxyalkanoates-Storing Bacteria

Agroindustrial by-products hold an enormous potential to be bioconverted into high-value-added products such as polyhydroxyalkanoates (PHA), a cost-effective alternative to conventional plastics. In this study, cheese whey, a highly abundant side stream of the cheese making process, was explored as a feasible substrate for the selection of a mixed culture highly enriched in PHA-storing bacteria using a sequencing batch reactor under an aerobic dynamic feeding regime. For that, the absence/presence of thiourea, magnesium and iron, as well as the application of two different organic loading rates (OLR), i.e., 60 and 80 CmM d−1, were tested. The results showed an improved culture selection when thiourea, magnesium and iron were added to the culture medium as well as when the highest OLR was applied. Under these conditions, the biomass achieved a maximum PHA storage of 54% and a PHA production rate of 4.81 Cmmol-PHA L−1 h−1. Additionally, the study of the microbial community showed that during this period of maximum productivity, the biomass was enriched in Azoarcus and Amaricoccus bacterial species. Conclusively, cheese whey can be considered a good feedstock to efficiently select a mixed culture with high potential to accumulate PHA and a good way to give this by-product added value.

Application of Immersed Membrane Bioreactor for Semi-Continuous Production of Polyhydroxyalkanoates from Organic Waste-Based Volatile Fatty Acids.

Volatile fatty acids (VFAs) appear to be an economical carbon feedstock for the cost-effective production of polyhydroxyalkanoates (PHAs). The use of VFAs, however, could impose a drawback of substrate inhibition at high concentrations, resulting in low microbial PHA productivity in batch cultivations. In this regard, retaining high cell density using immersed membrane bioreactor (iMBR) in a (semi-) continuous process could enhance production yields. In this study, an iMBR with a flat-sheet membrane was applied for semi-continuous cultivation and recovery of Cupriavidus necator in a bench-scale bioreactor using VFAs as the sole carbon source. The cultivation was prolonged up to 128 h under an interval feed of 5 g/L VFAs at a dilution rate of 0.15 (d-1), yielding a maximum biomass and PHA production of 6.6 and 2.8 g/L, respectively. Potato liquor and apple pomace-based VFAs with a total concentration of 8.8 g/L were also successfully used in the iMBR, rendering the highest PHA content of 1.3 g/L after 128 h of cultivation. The PHAs obtained from both synthetic and real VFA effluents were affirmed to be poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a crystallinity degree of 23.8 and 9.6%, respectively. The application of iMBR could open an opportunity for semi-continuous production of PHA, increasing the feasibility of upscaling PHA production using waste-based VFAs.

The Isolation, Screening, and Characterization of Polyhydroxyalkanoate-Producing Bacteria from Hypersaline Lakes in Kenya

Extremophilic microorganisms such as those that thrive in high-salt and high-alkaline environments are promising candidates for the recovery of useful biomaterials including polyhydroxyalkanoates (PHAs). PHAs are ideal alternatives to synthetic plastics because they are biodegradable, biocompatible, and environmentally friendly. This work was aimed at conducting a bioprospection of bacteria isolated from hypersaline-alkaliphilic lakes in Kenya for the potential production of PHAs. In the present study, 218 isolates were screened by Sudan Black B and Nile Red A staining. Of these isolates, 31 were positive for PHA production and were characterized using morphological, biochemical, and molecular methods. Through 16S rRNA sequencing, we found that the isolates belonged to the genera Arthrobacter spp., Bacillus spp., Exiguobacterium spp., Halomonas spp., Paracoccus spp., and Rhodobaca spp. Preliminary experiments revealed that Bacillus sp. JSM-1684023 isolated from Lake Magadi had the highest PHA accumulation ability, with an initial biomass-to-PHA conversion rate of 19.14% on a 2% glucose substrate. Under optimized fermentation conditions, MO22 had a maximum PHA concentration of 0.516 g/L from 1.99 g/L of cell dry weight and 25.9% PHA conversion, equivalent to a PHA yield of 0.02 g/g of biomass. The optimal PHA production media had an initial pH of 9.0, temperature of 35 °C, salinity of 3%, and an incubation period of 48 h with 2.5% sucrose and 0.1% peptone as carbon and nitrogen sources, respectively. This study suggests that bacteria isolated from hypersaline and alkaliphilic tropical lakes are promising candidates for the production of polyhydroxyalkanoates.

Hazop Analysis of a Bioprocess for Polyhydroxyalkanoate (PHA) Production from Organic Waste: Part B

The production of polyhydroxyalkanoates (PHAs) from industrial waste streams has attracted the attention of researchers and process industries because they could replace traditional plastics. The integrated treatment of civil wastewater along with organic solid wastes in a novel “urban biorefinery” is a very important option to implement a synergic treatment of all relevant bio-waste streams. The development of new biotech processes should consider the occupational health and safety issues from the initial design stages. Among the process hazards analysis techniques, HAZard and OPerability (HAZOP) methodology is widely used for studying both the processes hazards and their operability problems, by exploring the effects of any deviations from design conditions. In the present study, a modified version of HAZOP methodology has been applied to a three-step process developed at pilot scale in the Treviso municipal wastewater treatment plant in order to produce PHA. This paper (part B) shows the results of HAZOP analysis applied to the second process step aimed at culturing the activated sludge under periodic feeding conditions into a sequencing batch reactor (SBR). The analysis applied to the process conditions, corresponding to the maximum PHA content in the biomass, has led to the identification of technical solutions to mitigate the main occupational risks.

Hazop Analysis of a Bioprocess for Polyhydroxyalkanoate (PHA) Production from Organic Waste: Part A

The number of bioprocesses for the circular economy of organic waste has grown in recent years. Implementation of new processes and technologies should consider occupational health and safety issues from the initial design stages. Among the process hazards analysis techniques, HAZard and OPerability (HAZOP) methodology is widely used for studying both the process’s hazards and their operability problems, by exploring the effects of any deviations from design conditions. In the present study, a modified version of HAZOP methodology has been applied to a three-steps process developed at pilot scale in the Treviso municipal wastewater treatment plant in order to produce polyhydroxyalkanoate (PHA) as the final high value product. This paper shows the results of HAZOP analysis applied to the first process step (acidogenic fermentation) aimed at volatile fatty acids production. The analysis has been applied to the process conditions corresponding to the maximum PHA content in the biomass. The HAZOP study results showed that this methodology allowed a comprehensive exploration of conventional chemical engineering process hazards and biological hazards. Final piping and instrumentation diagrams (P&IDs) for acidogenic fermentation have been designed, identifying all prevention measures aimed at managing the hazard and operability issues. The P&ID shows the interconnection of equipment and the instrumentation required for controlling the process.

Strategy for economical and enhanced polyhydroxyalkanoate production from synergistic utilization of palm oil and derived wastewater by activated sludge

The potential of palm oil and derived wastewater pretreated by enzyme as co-substrates to accumulate polyhydroxyalkanoate (PHA) rich in short and medium-chain-length monomers under two feeding strategies was evaluated batchwise through mixed microbial cultures (MMCs) in activated sludge. A terpolymer with the maximum PHA content of 30.5 wt%, volumetric yield of 0.372 g COD/g COD and composition of ca. 84.7 ∼ 97.4/0.5 ∼ 1.6/2.1 ∼ 13.7 (3-hydroxybutyrate/ 3-hydroxyvalerate/ 3-hydroxyoctanoate, %) was achieved as a result of co-substrate incorporation. From the perspective of economic benefits, PHA accumulated via adopting strategy of supplementing carbon source to the same initial concentration per cycle saved 42.7 % of carbon consumption, along with a reduction in culture time (72 h). The above discoveries signify that the combination of palm oil and derived wastewater plus MMCs provides an alternative to the plastics industries for a more sustainable and efficient utilization of biological resources and an economic PHA accumulation approach.

Molecular Characterization, Optimization and Production of PHA by Indigenous Bacteria Using Alternative Nutrient Sources as Substrate

Polyhydroxyalkanoates (PHA) are renewable, biodegradable biopolymer intracellularly accumulated by wide array of microorganisms as carbon reserve. This study investigates the influence of various cultural conditions on PHA production by a recently isolated local species under submerged fermentation. Six PHA producing strains were identified by 16S rDNA gene sequencing and strain Priestia flexa OWO1 showed satisfactory PHA productivity. The effects of production parameters were investigated and extraction of PHA was carried out using sodium hypochlorite method and maximum amount was detected after 72h. Maximum PHA production was obtained at incubation period of 48h, pH of 7.0 and temperature of 30oC. Amongst the hydrolysate of agro waste used, brewers spent grain (BSG) gave maximum yield of 3.01g/L while beans bran powder gave the highest PHA yields of 3.9 g/L amongst the organic nitrogen sources tested. Analysis of the crude PHA by Fourier Transform Infrared Spectroscopy (FT-IR) showed the presence of methyl, methylene as well as carbonyl functional groups. PHA production was higher after optimizing the production conditions as compared to basal medium therefore the utilization of these cheap renewable resources as alternative substrates for production of PHA make the process cost effective and sustainable.

Aerobic granulation for polyhydroxyalkanoates accumulation using organic waste leachates

This work aimed to evaluate polyhydroxyalkanoates (PHA)-accumulating aerobic granular sludge (AGS) production using an inoculum of activated sludge and a prefermented medium consisting of leachates from the anaerobic hydrolysis of the organic fraction of municipal solid waste (OFMSW). Operating conditions induced the evolution in the biomass structure to obtain aerobic granules with an average diameter of 1 mm within the first 45 days. This process resulted in remarkable evolution in the settling properties, with a four-fold improvement in the sludge volume index (SVI) and the zone settling velocity (Vs), as well as a considerable increase in the density during the same period. Moreover, AGS exhibited a maximum PHA accumulation capacity of 0.215 g-PHA/g-VSS, which was two-fold higher than in the inoculum, indicating the enrichment of the biomass on PHA-accumulating microorganisms as a result of the application of the anaerobic feeding of the substrate and the operation with long famine periods; operating conditions reported as favorable for both, the cultivation of stable AGS and the selection biopolymers-accumulating microorganisms. However, the carbon balance revealed that VFA from the leachates was preferably used for EPS synthesis instead of PHA production, showing that microorganisms in AGS absorb organic carbon to convert it into EPS for internal structure maintenance.