Polyhydroxyalkanoates Yield Research Articles

Organic removal and synthesis of biopolymer from synthetic oily bilge water using the novel mixed bacterial consortium

Synthetic oily bilge water (OBW) treatment and subsequent production of biopolymer were studied by using a sequential batch reactor (SBR). The effect of various influencing parameters such as solids retention time (SRT), cycle time (CT), substrate concentration, pH level on the organic removal and synthesis of polyhydroxyalkanoates (PHA) was examined by novel soil bacteria isolated from hydrocarbon contaminated site near Karaikal port, India. The isolates were identified as Pseudomonas tuomuerensis and Pseudomonas nitroreducens using 16S rRNA. Sudan Black B staining was performed to visualize the presence of PHA. The experimental results showed that a decrease in substrate concentration to 5000 mg/L of soluble COD (CODs) showed maximum organic removal (81%) and maximum PHA yields of its cell dry mass (81%). The PHA yield was maximum at SRT of 5 d, pH = 7 and CT of 24 h. The produced PHA was characterized by using FTIR, XRD and SEM analysis.

Deletion of 76 genes relevant to flagella and pili formation to facilitate polyhydroxyalkanoate production in Pseudomonas putida.

Pseudomonas putida KT2442, a natural producer of polyhydroxyalkanoate, spends a lot of energy and carbon sources to form flagella and pili; therefore, deleting the genes involved in the biosynthesis and assembly of flagella and pili might improve PHA productivity. In this study, two novel deletion systems were constructed in order to efficiently remove the 76 genes involved in the biosynthesis and assembly of flagella and pili in P. putida KT2442. Both systems combine suicide-plasmid-based homologous recombination and mutant lox site-specific recombination and involve three plasmids. The first includes pK18mobsacB, pWJW101, and pWJW102; and the second includes pZJD29c, pDTW202, and pWJW103. These newly constructed systems were successfully used to remove different gene clusters in P. putida KT2442 and showed a high deletion efficiency (above 90%) whether for the second-round or the third-round recombination. Both systems could efficiently delete the gene PP4378 encoding flagellin in putida KT2442, resulting in the mutant strain WJPP01. The second system was used to remove the pili-forming gene cluster PP2357-PP2363 in putida KT2442, resulting in the mutant strain WJPP02, and also used to remove the flagella-forming gene cluster PP4329-PP4397 in WJPP02, resulting in the mutant strain WJPP03. Compared with the wild-type KT2442, the 1.2% genome reduction mutant WJPP03 grew faster, lacked flagella and motility, showed sharply decreased biofilm and 3',5'-cyclic diguanylic acid (c-di-GMP), but accumulated more polyhydroxyalkanoate. The biomass, polyhydroxyalkanoate yield, and content of WJPP03 increased 19.1, 73.4, and 45.6%, respectively, with sodium hexanoate supplementation, and also increased 11.4, 53.6, and 37.9%, respectively, with lauric acid supplementation.

Bioconversion of plant biomass hydrolysate into bioplastic (polyhydroxyalkanoates) using Ralstonia eutropha 5119

Pretreatment of lignocellulosic biomass results in the formation of byproducts (furfural, hydroxymethylfurfural [HMF], vanillin, acetate etc.), which affect microbial growth and productivity. Furfural (0.02%), HMF (0.04%), and acetate (0.6%) showed positive effects on Ralstonia eutropha 5119 growth and polyhydroxyalkanoate (PHA) production, while vanillin exhibited negative effects. Response optimization and interaction studies between the variables glucose, ammonium chloride, furfural, HMF, and acetate using the response surface methodology resulted in maximum PHA production (2.1 g/L) at optimal variable values of 15.3 g/L, 0.43 g/L, 0.04 g/L, 0.05 g/L, and 2.34 g/L, respectively. Different lignocellulosic biomass hydrolysates (LBHs), including barley biomass hydrolysate (BBH), Miscanthus biomass hydrolysate (MBH), and pine biomass hydrolysate (PBH), were evaluated as potential carbon sources for R. eutropha 5119 and resulted in 1.8, 2.0, and 1.7 g/L PHA production, respectively. MBH proved the best carbon source, resulted in higher biomass (Yx/s, 0.31 g/g) and PHA (Yp/s, 0.14 g/g) yield.

Biolytic extraction of poly(3-hydroxybutyrate) from Bacillus megaterium Ti3 using the lytic enzyme of Streptomyces albus Tia1.

The applicability of Streptomyces sp. cell lytic enzymes for devising a simple and competent biological polyhydroxyalkanoate (PHA) recovery approach from Bacillus megaterium cells was investigated. B. megaterium strain Ti3 produced 50% (w/w) PHA using glucose as carbon source. The intracellular PHA was recovered employing a non-PHA accumulating actinomycetes (Tia1) identified as Streptomyces albus, having potent lytic activity against living and heat inactivated B. megaterium. Interestingly, maximum biomass (2.53 ± 0.6 g/L by 24 h) of the lytic actinomycete was obtained in PHA production medium itself thus circumventing the prior actinomycete acclimatization just by co-inoculation with B. megaterium as an inducer. Maximum lytic activity was observed at pH 6.0, 40 °C, 220 mg of biomass and 33.3 mL of concentrated culture filtrate in a 100 mL reaction mixture. Preliminary biochemical investigations confirmed the proteolytic and caseinolytic nature of the lytic enzyme. PHA yield of 0.55 g/g by co-inoculation extraction approach was comparable with the conventional sodium hypochlorite based extraction method. Interestingly, S. albus also demonstrated a broad spectrum lytic potential against varied Gram-negative and Gram-positive PHA producers highlighting the extensive applicability of this biolytic PHA recovery approach. The lytic enzyme retained almost 100% relative activity on storage at −20 °C upto two months. 1H Nuclear magnetic resonance analysis of the extracted polymer confirmed it as a homopolymer composed of 3-hydroxybutyrate monomeric units. This is the first report on Streptomyces sp. based biological and eco-friendly, intracellular PHA recovery from Bacillus spp.

Biosynthesis and characterization of polyhydroxyalkanoate from marine Bacillus cereus MCCB 281 utilizing glycerol as carbon source

Polyhydroxyalkanoates (PHAs) are aliphatic polyesters produced by bacteria from renewable resources which serve as a substitute of synthetic plastics. In the present study isolation, screening, identification of PHA producing bacteria from marine water samples and optimization of process variables for increased PHA production were accomplished. The potent isolate identified as Bacillus cereus MCCB 281 synthesized PHA co-polymer with 13 mol% 3-hydroxyvalerate in presence of glycerol. Process parameters optimized using central composite design for enhanced PHA production showed 1.5 fold higher PHA yield. Cell dry weight of 3.72 ± 0.04 g L−1, PHA yield 2.54 ± 0.07 g L−1 and PHA content of 68.27 ± 1.2% (w/w) was achieved in fermenter at the optimized conditions. Purified polymer was characterized by Fourier-transform infrared spectroscopy, Nuclear magnetic resonance spectroscopy, Gas chromatography–Mass spectrometry, X-ray powder diffraction techniques and molecular weight of PHA was found to be 2.56 × 105 Da. PHA nanoparticles with average particle size 179 nm were synthesized for medical applications and biocompatibility analysis was performed with L929 mouse fibroblast cell line. This is the first report of a moderately halophilic B. cereus, which utilizes glycerol as the sole carbon source for PHA co-polymer production.

Polyhydroxyalkanoate Producing Potential of Saccharomyces cerevisiae

Polyhydroxyalkanoates (PHAs) are inclusion bodies accumulated by some microorganisms as reserve material under unbalanced growth condition such as limited oxygen, nitrogen, phosphorous or sulphur and excess carbon source. Saccharomyces cerevisiae strains were screened for Polyhydroxyalkanoates (PHA) producing potential using plate assay technique with Sudan Black B stain. Saccharomyces cerevisiae efficiency for PHA production was analysed utilizing sawdust as carbon source and the production rate was compared with glucose (control). Thus, PHA synthesising enzymes, PHA carbon chain distributions and concentrations were determined using gas chromatography flame ionization detector (GCFID) while microbial growth (biomass yield) during production was determined using Uv-Visible spectrophotometric technique at 600 nm. PHA was extracted from Saccharomyces cerevisiae cells using solvent extraction technique and the extract was further dissolved using acetone derivatisation process. PHA-synthesising enzymes such as Glyceraldehyde-3-phosphate dehydrogenase, Pyruvate dehydrogenase, 3-Ketothiolase, Acetoacetyl-CoA reductase, 3-Ketoacyl reductase and Polyhydroxyalkanoate synthase were extracted from cell-free supernatant obtained from glucose and sawdust media. Saccharomyces cerevisiae cells grown in sawdust medium had the highest PHA yield of 75.12 % while 64.66 % PHA was obtained from cells grown in glucose medium. Consequently, utilization of Saccharomyces cerevisiae in limiting condition using agricultural residue could reduce the cost of industrial production of PHA required for plastic production due to its ability to accumulate the polymer intracellularly.

Mixed culture polyhydroxyalkanoate (PHA) synthesis from nutrient rich wet oxidation liquors

Organic waste residues can be hydrothermally treated to produce organic acid rich liquors. These hydrothermal liquors are a potential feedstock for polyhydroxyalkanoate (PHA) production. We investigated the effect of dissolved oxygen concentration and substrate feeding regimes on PHA accumulation and yield using two hydrothermal liquors derived from a mixture of primary and secondary municipal wastewater treatment sludge and food waste. The enriched culture accumulated a maximum of 41% PHA of cell dry weight within 7 h; which is among the highest reported for N and P rich hydrothermal liquors. Recovered PHA was 77% polyhydroxybutyrate and 23% polyhydroxyvalerate by mass. The families Rhodocyclaceae (84%) and Saprospiraceae (20.5%) were the dominant Proteobacteria (73%) in the enriched culture. The third most abundant bacterial genus, Bdellovibrio, includes species of known predators of PHA producers which may lead to suboptimal PHA accumulation. The PHA yield was directly proportional to DO concentration for ammonia stripped liquor (ASL) and inversely proportional to DO concentration for low strength liquor (LSL). The highest yield of 0.50 Cmol PHA/Cmol substrate was obtained for ASL at 25% DO saturation. A progressively increasing substrate feeding regime resulted in increased PHA yields. These findings demonstrate that substrate feeding regime and oxygen concentration can be used to control the PHA yield and accumulation rate thereby enhancing PHA production viability from nutrient rich biomass streams.

Combined polyhydroxyalkanoates (PHA) and 1,3-propanediol production from crude glycerol: Selective conversion of volatile fatty acids into PHA by mixed microbial consortia

Crude glycerol is an important by-product of the biodiesel industry, which can be converted into volatile fatty acids (VFA) and/or 1,3-propanediol (1,3-PDO) by fermentation. In this study, a selective conversion of VFA to polyhydroxyalkanoates (PHA) was attained while leaving 1,3-PDO in the supernatant by means of mixed microbial consortia selection strategies. The process showed highly reproducible results in terms of PHA yield, 0.99 ± 0.07 Cmol PHA/Cmol S (0.84 g COD PHA/g COD S), PHA content (76 ± 3.1 g PHA/100 g TSS) and 1,3-PDO recovery (99 ± 2.1%). The combined process had an ultimate yield from crude glycerol of 0.19 g COD PHA and 0.42 g COD 1,3-PDO per g of input COD. The novel enrichment strategy applied for selectively transforming fermentation by-products into a high value product (PHA) demonstrates the significance of the enrichment process for targeting specific bio-transformations and could potentially prove valuable for other biotechnological applications as well.

A novel biological recovery approach for PHA employing selective digestion of bacterial biomass in animals.

Polyhydroxyalkanoate (PHA) is a family of microbial polyesters that is completely biodegradable and possesses the mechanical and thermal properties of some commonly used petrochemical-based plastics. Therefore, PHA is attractive as a biodegradable thermoplastic. It has always been a challenge to commercialize PHA due to the high cost involved in the biosynthesis of PHA via bacterial fermentation and the subsequent purification of the synthesized PHA from bacterial cells. Innovative enterprise by researchers from various disciplines over several decades successfully reduced the cost of PHA production through the efficient use of cheap and renewable feedstock, precisely controlled fermentation process, and customized bacterial strains. Despite the fact that PHA yields have been improved tremendously, the recovery and purification processes of PHA from bacterial cells remain exhaustive and require large amounts of water and high energy input besides some chemicals. In addition, the residual cell biomass ends up as waste that needs to be treated. We have found that some animals can readily feed on the dried bacterial cells that contain PHA granules. The digestive system of the animals is able to assimilate the bacterial cells but not the PHA granules which are excreted in the form of fecal pellets, thus resulting in partial recovery and purification of PHA. In this mini-review, we will discuss this new concept of biological recovery, the selection of the animal model for biological recovery, and the properties and possible applications of the biologically recovered PHA.

Production and optimization of polyhydroxyalkanoates from non-edible Calophyllum inophyllum oil using Cupriavidus necator

Polyhydroxyalkanoates (PHA) are biodegradable polymers found in the cellular masses of a wide range of bacterial species and the demand for PHA is steadily growing. In this work we have produced PHA from a low-cost substrate, Calophyllum inophyllum oil, using Cupriavidus necator. Effects of various process parameters such as Oil concentration, Nitrogen source and inoculum size on the production of PHA were studied using Response Surface Methodology. A quadratic equation was used in the model to fit the experimental data. It was found that the model could satisfactorily predict the PHA yield (R2=99.17%). Linear, quadratic and interaction terms used in the model were found to be statistically significant. Maximum PHA yield of 10.6gL−1 was obtained under the optimized conditions of oil concentration - 17.5%, inoculum concentration - 50mL/L and nitrogen content - 1.125gL−1, respectively. The product obtained was characterized using FTIR and NMR to confirm that it was PHA. The results demonstrate that C. inophyllum oil, a non-edible oil, can be potentially used as a low-cost substrate for the production of PHA.

Biogenic PHA nanoparticle synthesis and characterization from Bacillus subtilis NCDC0671 using orange peel medium

ABSTRACTThe present research work was initiated to synthesize biogenic polyhydroxyalkanoate (PHA) nanoparticles from Bacillus subtilis NCDC0671 using orange peel medium. Sequential and systematic optimization of bioprocess variables was performed using “one-factor-at-a-time” approach for maximizing PHA yield. Maximum PHA yield was achieved under optimized conditions of temperature (37°C), pH (7), carbon source (sucrose), and nitrogen source (beef extract) on 72 h of fermentation using B. subtilis NCDC0671. PHA nanoparticles were synthesized using triple emulsion method and conjugated with drug levofloxacin. Dialysis method was used to evaluate the in vitro drug releasing efficacy of PHA–levofloxacin nanoparticles.

Polyhydroxyalkanoates (PHA) production by photoheterotrophic microbial consortia: Effect of culture conditions over microbial population and biopolymer yield and composition

Three microbial consortia (C2, C4, C5) grown under photoheterotrophic conditions assimilated acetate and butyrate, as individual and mixed substrates. By controlling the culture conditions, it was possible to manipulate the microbial population composition and thus the yield of polyhydroxyalkanoates (PHA) accumulation. Under limited ammonium conditions, pH control, and a sequential two-step process, C2 and C4 produced PHA. C4 showed the highest production of 44% of the cell dry mass (CDM), close to the theoretical value calculated with a stoichiometric balance. Analysis of the confocal microscopy images confirmed the accumulated biopolymer percentages produced by each consortium, and it was in close correlation with microbial distribution and substrate consumption pattern. 1H, 13C, NMR, and MALDI-TOF spectra identified the primary structure of the obtained biopolymers as copolymers of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV). This composition allows for better mechanical properties compared to the PHB homopolymer. Microbial characterization showed a similar microbial population with different proportions for C2 and C4. The highest PHA production in C4 was associated with higher abundances of PHA producers, including Clostridium (29%), Pseudomonas (8%) and Rhodopseudomonas (5%). Both microbial consortia showed that a portion of their microbial populations were able to perform syntrophic reactions (Dysgonomonas and Clostridium).

Polyhydroxyalkanoates (PHA) production from fermented crude glycerol: Study on the conversion of 1,3-propanediol to PHA in mixed microbial consortia

Crude glycerol, a by-product from the biodiesel industry, can be converted by mixed microbial consortia into 1,3-propanediol (1,3-PDO) and volatile fatty acids. In this study, further conversion of these main products into polyhydroxyalkanoates (PHA) was investigated with the focus on 1,3-PDO. Two different approaches for the enrichment of PHA accumulating microbial consortia using an aerobic dynamic feeding strategy were applied. With the first approach, where nitrogen was present during the whole cycle, no net production of PHA from 1,3-PDO was observed in the fermented effluent, not even in a nitrogen-limited PHA accumulation assay. Nevertheless, experiments in synthetic substrates revealed that the conversion of 1,3-PDO to PHA was possible under nitrogen limiting conditions. Thus, a different enrichment strategy was formulated where nitrogen was limited during the feast phase to stimulate the storage response. Nitrogen was still supplied during the famine phase. With the latter strategy, a net production of PHA from 1,3-PDO was observed at a yield of 0.24 Cmol PHA/Cmol 1,3-PDO. The overall yield from the fermented effluent was 0.42 Cmol PHA/Cmol substrate. Overall, the PHA yield from 1,3-PDO seemed to be limited, similarly to when using glycerol as a substrate, by a decarboxylation step and accumulation of other storage polymers such as glycogen, and possibly, lipid inclusions.

Co-synthesis of medium-chain-length polyhydroxyalkanoates and CdS quantum dots nanoparticles in Pseudomonas putida KT2440

Microbial polymers and nanomaterials production is a promising alternative for sustainable bioeconomics. To this end, we used Pseudomonas putida KT2440 as a cell factory in batch cultures to coproduce two important nanotechnology materials– medium-chain-length (MCL)-polyhydroxyalkanoates (PHAs) and CdS fluorescent nanoparticles (i.e. quantum dots [QDots]). Due to high cadmium resistance, biomass and PHA yields were almost unaffected by coproduction conditions. Fluorescent nanocrystal biosynthesis was possible only in presence of cysteine. Furthermore, this process took place exclusively in the cell, displaying the classical emission spectra of CdS QDots under UV-light exposure. Cell fluorescence, zeta potential values, and particles size of QDots depended on cadmium concentration and exposure time. Using standard PHA-extraction procedures, the biosynthesized QDots remained associated with the biomass, and the resulting PHAs presented no traces of CdS QDots. Transmission electron microscopy located the synthesized PHAs in the cell cytoplasm, whereas CdS nanocrystals were most likely located within the periplasmic space, exhibiting no apparent interaction. This is the first report presenting the microbial coproduction of MCL-PHAs and CdS QDots in P. putida KT2440, thus constituting a foundation for further bioprocess developments and strain engineering towards the efficient synthesis of these highly relevant bioproducts for nanotechnology.

A Statistical approach to optimize the production of Polyhydroxyalkanoates from Wickerhamomyces anomalus VIT-NN01 using Response Surface Methodology

Polyhydroxyalkanoates (PHAs) are three-level group of biodegradable polymers and attractive substitutes over conventional plastics to avoid the pollution problems. The yeast strain isolated from sugarcane juice, identified as Wickerhamomyces anomalus VIT-NN01, was used for the production of polyhydroxyalkanoates (PHA). Response surface methodology (RSM), three-level six variables Box-Behnken design (BBD), was employed to optimize the factors such as pH 8.0, temperature 37°C, sugarcane molasses (35g/L) supplemented with co-substrate palm oil (0.5%),corn steep liquor (2%) after a period of 96h of incubation for the maximum yield (19.50±0.3g/L) of PHA. It was well in close agreement with the predicted value obtained by RSM model yield (19.55±0.1g/L).Characterization of the extracted polymer was done using FTIR, GC–MS, XRD, TGA and AFM analysis. NMR spectroscopic analysis revealed that the biopolymer was poly (3-hydroxybutyrate-co-3-hydroxyvalerate), copolymer of PHA. This is the first report on optimization of PHA production using yeast strain isolated from natural sources.

Biogas-based polyhydroxyalkanoates production by Methylocystis hirsuta: A step further in anaerobic digestion biorefineries

The potential of biogas (with and without H2S) and volatile fatty acids (VFAs) to support microbial growth and accumulation of polyhydroxyalkanoates (PHAs) in type II methanotrophs was evaluated batchwise under aerobic conditions. Methylocystis hirsuta was able to grow on artificial biogas (70% CH4, 29.5% CO2, 0.5% H2S) and accumulate PHA up to 45 ± 1% (wt.%) under N-limited conditions. The presence of CO2 and H2S did not significantly influence the growth and PHA synthesis in M. hirsuta compared to control tests provided with pure CH4 at similar concentrations. Likewise, the addition of VFAs to the cultivation broth at initial concentrations of 100–200 mg L−1 did not hamper the growth of this strain on artificial biogas. Indeed, the addition of 10% extra carbon in the form of individual VFAs resulted in an increase in the maximum PHA yield and final PHA content up to 0.45–0.63 gPHA gSubstrate 1 and 48–54% (wt.%), respectively, at the expense of a higher energy demand. Valeric acid supplementation supported the highest 3-hydroxyvalerate content (13.5%) within the biocomposite. In this context, this study demonstrated for the first time that 3-hydroxyvalerate synthesis by M. hirsuta did not depend on CH4 assimilation.

Enhanced polyhydroxyalkanoate (PHA) production from the organic fraction of municipal solid waste by using mixed microbial culture

BackgroundIn Europe, almost 87.6 million tonnes of food waste are produced. Despite the high biological value of food waste, traditional management solutions do not consider it as a precious resource. Many studies have reported the use of food waste for the production of high added value molecules. Polyhydroxyalkanoates (PHAs) represent a class of interesting bio-polyesters accumulated by different bacterial cells, and has been proposed for production from the organic fraction of municipal solid waste (OFMSW). Nevertheless, until now, no attention has been paid to the entire biological process leading to the transformation of food waste to organic acids (OA) and then to PHA, getting high PHA yield per food waste unit. In particular, the acid-generating process needs to be optimized, maximizing OA production from OFMSW. To do so, a pilot-scale Anaerobic Percolation Biocell Reactor (100 L in volume) was used to produce an OA-rich percolate from OFMSW which was used subsequently to produce PHA.ResultsThe optimized acidogenic process resulted in an OA production of 151 g kg−1 from fresh OFMSW. The subsequent optimization of PHA production from OA gave a PHA production, on average, of 223 ± 28 g kg−1 total OA fed. Total mass balance indicated, for the best case studied, a PHA production per OFMSW weight unit of 33.22 ± 4.2 g kg−1 from fresh OFMSW, corresponding to 114.4 ± 14.5 g kg−1 of total solids from OFMSW. PHA composition revealed a hydroxybutyrate/hydroxyvalerate (%) ratio of 53/47 and Mw of 8∙105 kDa with a low polydispersity index, i.e. 1.4.ConclusionsThis work showed how by optimizing acidic fermentation it could be possible to get a large amount of OA from OFMSW to be then transformed into PHA. This step is important as it greatly affects the total final PHA yield. Data obtained in this work can be useful as the starting point for considering the economic feasibility of PHA production from OFMSW by using mixed culture.

Poly(3-hydroxybutyrate)-P(3HB): Review of Production Process Technology

Abstract For decades, conventional plastics obtained from fossil-based sources have been used indiscriminately due to their durability and resistance. However, their use is problematic because of their rapid disposability and slow degradation. Growing scientific interest in the environmental issues associated with rising plastics consumption has become of increasing importance in the search for biodegradable substitutes. Poly (3-hydroxybutyrate) (P(3HB)) is one of the most studied and characterized microbial biopolymers from the family of polyhydroxyalkanoates (PHAs). Its main features are rapid biodegradability, low toxicity, and biocompatibility. Global production of PHAs is approximately 100 tons/year, and is expected to grow to 500,000 tons/year by 2020. Researchers have sought to increase the intracellular accumulation and polymer yield of PHAs by screening strains and improving the cultivation and operating procedures employed during the production processes. Synthesis of P(3HB) normally involves tw...

Enhanced polyhydroxyalkanoate production by mixed microbial culture with extended cultivation strategy

Low biomass output is a crucial reason for low polyhydroxyalkanoate (PHA) production in mixed microbial cultures (MMCs) PHA process. In this research, an extended cultivation strategy was proposed to rapidly expand the biomass yield of PHA accumulating MMCs and conserve the PHA accumulating ability simultaneously. High PHA content of the cultivated MMCs of 71.4% and 66.7% (higher than 62.1% of the seed biomass) in batch assays and biomass magnification of 43 and 52 were obtained after 10days of extended cultivation with and without sludge discharge, respectively. By embedding the extended cultivation process into the production process, a highly competitive PHA production performance in terms of overall PHA storage yield (0.49g CODPHA/gCODVFA) and volumetric productivity (1.21gPHA/L/d with final cell density of 17.22g/L) was achieved. The proposed PHA production process based on the extended cultivation can be a promising choice in industrial scale practice.

Formulation and optimization of a novel media comprising rubber seed oil for PHA production

Formulation and optimization of a media comprising rubber seed oil11RSO: Rubber seed oil, PHA: Polyhydroxyalkanoates, DCE: Dry coconut cake extract, CDW: Cell dry weight (RSO) as a low cost substrate for polyhydroxyalkanoates (PHA) biosynthesis in the bacterial strain Bacillus cereus was implemented. The formulation study using general full factorial design concluded that 1.5% (v/v) RSO in distilled water is sufficient to obtain PHA content as high as 604.77mg/g cell dry weight and a total yield of 2.16g/L within a growth period of 72h at 150rpm. Response surface methodology based design was used for the optimization of production parameters. Accordingly, PHA content of 641.14mg/g cell dry weight and a total PHA yield 2.56g/L were obtained in 69.2h with RSO concentration of 1.567% (v/v) and an agitation of 130rpm. Characterization of the polymer was performed by Fourier transform infrared spectroscopy, X-ray diffraction crystallography, scanning electron microscopy, differential scanning calorimetry and thermogravimetric analysis. Scale up studies and industrialization of this media for PHA production will result in value addition to rubber seeds that are currently commercially insignificant.