Polyhydroxyalkanoates Yield Research Articles

Lab-Scale Optimization of Polyhydroxyalkanoate Production by Bacterial Strain cmg1415 on Local Cheap Substrates Using One Variable at a Time Approach

Production of polyhydroxyalkanoate (PHA) under optimum culture conditions using local cheap feedstocks is indispensable to overcome the current cost of PHA-based plastics. For this purpose, optimum culture conditions and cheap feedstocks were investigated to produce maximum yield of PHA in CMG1415. Maximum yield was obtained with sucrose or sugar beet as sole source of precursors for PHA in 8 days of incubation at 35 °C in a minimal medium adjusted at pH 7. Further, for maximum yield no mechanical shaking was needed. Local cheap feedstock such as sugar beet and molasses were found to play as significant carbon and nitrogen sources for maximum PHA yield. Bacterial plastic produced under these low-labor-cost culture conditions may to reduce the present cost of degradable bioplastic and be much effective alternate of nondegradable varieties of synthetic plastic.

Towards biodegradable polyhydroxyalkanoate production from wood waste: Using volatile fatty acids as conversion medium

Production of polyhydroxyalkanoate (PHA) via mixed microbial consortia is a potential economic alternative responding to the current demand for functional greener materials to replace traditional petroleum-basedpolymers. The goal of this study was to synthesize PHA using volatile fatty acids (VFAs) obtained from the co-fermentation of pretreated wood waste and sewage as carbon source. High PHA yield of 0.71 g COD PHA/g COD VFAs and PHA content of 50.3 g PHA/100 g VSS were obtained at VFAs ratio (even:odd) of 88:12 after seven cycles cultivation. Even acids were more suitable for accumulating PHA as the preferred carbon source than odd acids, resulting in 3-hydroxybutyrate being the main monomer. PHA production achieved to the highest value of about 2639 mg COD/L at 1400 mg COD/L VFAs concentration. The bacterial genera displayed a highly diverse of the microbial community for the synthesis of PHA.

Whey valorization for sustainable polyhydroxyalkanoate production by Bacillus megaterium: Production, characterization and in vitro biocompatibility evaluation

Polyhydroxyalkanoates (PHAs) are biodegradable biopolymers acclaimed as an eco-friendly substitute of hazardously polluting petrochemical plastics. Using industrial by-products as PHA feedstocks could improve its process economics and market implementation. Valorizing the plenteous, nutritive pollutant whey as PHA production feedstock would be an excellent whey management strategy. This study aimed at whole/crude whey valorization for value-added PHA production using B. megaterium Ti3 innate protease, alleviating pretreatments. Response surface methodology (RSM) media optimization ascertained whey (%) as the key influential factor (p < 0.05). The optimized and validated RSM model (R2, 0.991; desirability, 1) facilitated 12.2, 11.5 folds increased PHA yield (2.20 ± 0.11 g/L) and productivity (0.05 gPHA/L/h). A positive correlation (r2, 0.95 and 0.87) was observed amid the innate enzymes (protease and lipase) and PHA production. The PHA was characterized by 1H and 13C NMR, GPC, TGA, and was identified as poly (3-hydroxybutyrate) (P3HB) by NMR. A significantly reduced roughness (110 ± 5.6 nm); increased hydrophilicity (8.6 ± 0.3 and 8.7 ± 0.5%), protein adsorption (68.75 ± 2.55 μg/cm2) and 1.6 folds higher biocompatibility achieved on poly (ethylene glycol) (PEG) blending compared to neat P3HB films. This is the first report on B. megaterium innate enzyme based whey valorization to PHAs also demonstrating its biomedical applicability.

Glutamine-induced filamentous cells of Pseudomonas mediterranea CFBP-5447T as producers of PHAs.

Polyhydroxyalkanoates (PHAs) are considerable biopolymers that have gained an increasing biotechnological interest in different applications, although their industrial production presents several limitations. Filamentous bacterial cells could represent a possible strategy to increase PHA yield, since more abundant PHA inclusions can be stored in elongated than in rod-shaped cells. At first, we determined the optimal batch culture conditions to induce filamentation in Pseudomonas mediterranea CFBP-5447T, using glutamine, glycerol, glucose, and sodium octanoate, as the sole carbon source, at low- (100 rpm) or high- (250 rpm) shaking speeds. Successively, a fermentative process was set up using glutamine in a co-metabolic strategy with glycerol, and the PHAs production was compared in rod-shaped and filamentous cells. High glutamine concentrations (from 28 to 56 mM) were able to induce alone filamentation, whereas at lower glutamine concentrations (5-10 mM), the shaking speeds became critical to allow or not filamentous phenotype. PHA granule production was higher in filamentous than in rod-shaped cells, when glycerol (46.6 mM) was added to glutamine (5 mM) in co-metabolism, and fermentation was performed at a low-shaking speed. After extraction and precipitation, PHA yield was about two times higher in filamentous than that rod-shaped cells. Our results provide new insights into filament-inducing conditions and indicate a potential use of filamentous P. mediterranea CFBP-5447T cells to increase PHA yield. These findings could have great advantages in PHAs recovering during downstream processes, since the harvesting of elongated cells is much less time-consuming and energy expensive than required with rod-shaped cells.

Insights into the effect of different levels of crude oil on hydrolyzed polyacrylamide biotransformation in aerobic and anoxic biosystems: Bioresource production, enzymatic activity, and microbial function

The differences of crude oil recovery ratio resulted in different levels of crude oil in actual hydrolyzed polyacrylamide (HPAM)-containing wastewater. The effect of crude oil on HPAM biotransformation was explored from bioresource production, enzymatic activity and microbial function. In aerobic biosystems, the highest polyhydroxyalkanoate (PHA) yield (19.6%–40.2%) and dehydrogenase (DH) activity (4.06–8.32 mg·g–1 VSS) occurred in the 48th hour, and increased with crude oil concentration (0–400 mg·L–1). In anoxic biosystems, the highest PHA yield (24.5%–50.5%) and DH activity (3.24–6.69 mg·g–1 VSS) occurred in the 72nd hour, and increased with crude oil concentration. The higher substrate removal (38.5%–65.7%) occurred in aerobic biosystems, while the higher PHA accumulation occurred in anoxic biosystems. PHA yield, DH activity and HPAM removal were related. Microbial function related to HPAM biodegradation and PHA synthesis was discussed. The main function of Pseudomonas and Bacillus in aerobic biosystems was to degrade HPAM, and in anoxic biosystems was to synthesize PHA.

Production of polyhydroxyalkanoates and enrichment of associated microbes in bioreactors fed with rice winery wastewater at various organic loading rates

This study aimed to explore the production of polyhydroxyalkanoates (PHA) and selection of PHA-accumulating microorganisms in bioreactors fed with rice winery wastewater at various organic loading rates (OLRs). The substrate utilization, sludge properties, PHA synthesis and microbial community structure of three sequencing batch reactors were monitored. The results show the highest PHA yield (0.23 g/g) was achieved in one of the three reactors with an OLR of 2.4 g COD/L/d, in which Zoogloea was the most dominant PHA-accumulating microorganism. To quantify the PHA production and track the population changing profiles of the PHA-accumulating microorganisms in the long-term reactor operation, the Activated Sludge Model No. 3 was modified with two different heterotrophic microorganisms responding differently with the same substrate. The modeling results indicate that a moderate OLR (>2.4 gCOD/L/d) was beneficial for PHA production. The results are useful for understanding the PHA production from industrial wastewaters and selection of PHA-accumulating microorganisms.

Polyhydroxyalkanoates (PHA) production from fermented thermal-hydrolyzed sludge by PHA-storing denitrifiers integrating PHA accumulation with nitrate removal

Polyhydroxyalkanoates (PHA) production from fermented thermal-hydrolyzed sludge was conducted by mixed microbial cultures (MMCs) in the study. An MMC enriched in the species Brachymonas_denitrificans (60.18%) was selected under an aerobic feast/famine regime, which is capable of denitrification and accumulating PHA. To take advantage of the PHA-storing denitrifiers, an aerobic-feast/anoxic-famine regime was applied to integrate culture selection with denitrification. The results showed that cultures enriched under the regime exhibited a PHA storage capacity with PHA yield on VFA of 0.47 gCOD/gCOD and well denitrification performance achieving nitrate removal of 98%. Moreover, the aerobic-feast/anoxic-famine regime could originate a comparable maximum PHA content to the complete aerobic feast/famine regime (49.7 wt% versus. 47.1 wt%, respectively), yet reduce aeration energy input by 79% in the culture selection process. Finally, this study investigated the accumulation of nitrite and nitrous oxide during PHA based denitrification and the feasibility of integrating the process with wastewater treatment.

Polyhydroxyalkanoates (PHA) production from fermented thermal-hydrolyzed sludge by mixed microbial cultures: The link between phosphorus and PHA yields

Production of polyhydroxyalkanoates (PHA) from wastes has gained increasing attention for the related low costs and high environmental benefits. Phosphorus limitation is a potential strategy used to facilitate PHA production, yet excessive limitation was previously reported to cause negative effects. This study was the first to investigate the optimum phosphorus limitation for PHA accumulation from thermal-hydrolyzed sludge. The results showed that the maximum PHA content increased from 23 wt% to 51 wt% when phosphorus concentration was limited from 127.60 to 1.35 mg/L, indicating that a lower phosphorus concentration would promote maximum PHA accumulation. Batch tests performed with synthetic substrates (containing one specific VFA for each batch) confirmed that the effect of phosphorus content on PHA production was mainly devoted by the efficiency of the conversion of acetate to PHA. The PHA yields on acetate (YPHA/ac) were 0.68 and 0.05 Cmol/Cmol under phosphorus-limited (1 mg/L) and -excess (100 mg/L) conditions, respectively. A mathematical model was developed to describe the correlation between phosphorus concentration and YPHA/ac, which can fit the experimental data and predict the results properly. Finally, further (ammonium-) nitrogen restriction did not efficiently cause the additional improvement of PHA production under the conditions of phosphorus limitation.

Food wastes and sewage sludge as feedstock for an urban biorefinery producing biofuels and added‐value bioproducts

AbstractThe updated Bioeconomy Strategy document “A sustainable bioeconomy for Europe: strengthening the connection between economy, society and the environment”, which was issued by the European Commission in October 2018, encourages the exploitation of organic wastes according to a pyramidal hierarchy in which the extraction of valuable biomolecules, which will be used as they are or as precursors of high‐added‐value compounds, is a priority in biofuel production. This review considers a biorefinery platform in which food waste and sewage sludge are adopted to produce volatile fatty acids (VFAs) through a dark fermentation process. VFA fermentation is optimized by slightly acid pH (6–7), short hydraulic retention time (1–7 days) and high organic load rate (more than 10 gTS L−1 d−1). Attention has been focused on VFA exploitation for polyhydroxyalkanoate (PHA) production via a ‘feast and famine’ strategy performed in sequencing batch reactors. The obtained PHA yields are around 0.4–0.5 gPHA gCOD−1. Moreover, VFAs allow for the production of biofuels, such as hydrogen and methane, through single‐ or double‐staged anaerobic digestion. Innovative bioelectrochemical upgrade strategies for biogas helps producers to obtain biomethane for the automotive sector. Moreover, biogas has recently been tested for the production of polyhydroxybutyrate, a biodegradable and biocompatible thermoplastic made by microorganisms from C1 carbon sources (CO2 and CH4). Digestates from anaerobic bioreactors are still rich in nitrogen and phosphorus compounds. These latter compounds have been identified as critical raw materials due to their low availability in the European Union and to increasing demand from the growing global population. Thus, nutrient recovery from digestate allows users to close the loop of the ‘circular economy’ approach. © 2019 Society of Chemical Industry

Biosynthesis and statistical optimization of polyhydroxyalkanoate (PHA) produced by Bacillus cereus VIT-SSR1 and fabrication of biopolymer films for sustained drug release

Polyhydroxyalkanoates are a fascinating group of biological polymers, which have attracted extensive attention. An effectual PHB accumulating Bacillus cereus strain VIT-SSR1 was isolated from industrial effluent contaminated site. Plackett-Burman design was used to screen the critical factors affecting PHA production. Response surface method was employed to evaluate the interactive effects between the independent variables. The Central composite design was performed to optimize the concentrations of Molasses, ammonium sulphate and initial pH. A PHA content of (1.42 ± 0.01) g/L and a maximum PHA yield of (40.3 ± 0.77) % was obtained on implementing the optimized conditions. The produced biopolymer was analysed using Fourier transform infrared spectroscopy (FT-IR) and Gas chromatography-mass spectrometry analysis(GC–MS) and the thermal properties of the biopolymer were evaluated by Thermogravimetric analysis (TGA), and from the Nuclear magnetic Resonance (NMR) analysis the biopolymer was identified to be polyhydroxybutyrate (PHB). PHB-chitosan blends were prepared and tested for biocompatibility by MTT assay on L929 mouse fibroblast cell lines. Curcumin, a well-known drug was loaded onto PHB-chitosan films and their drug release pattern was observed. Curcumin showed a sustained mode of drug release. PHB films are biocompatible and can act as a potent polymer matrix for drug release studies.

Reconsideration on the effect of nitrogen on mixed culture polyhydroxyalkanoate production toward high organic loading enrichment history

In most of the operating strategies for mixed microbial cultures polyhydroxyalkanoate (PHA) production, moderate organic loads and low nitrogen concentrations are used, however, the real waste streams contain variable concentrations of carbon and nitrogen. To evaluate the effect of enrichment history on PHA producer and production the various carbon and nitrogen levels were utilized during the accumulation phase. Different operating strategies were applied in three sequencing batch reactors (SBRs) subjected to aerobic dynamic feeding. The maximum PHA production of the enriched cultures under nutrient excess, limitation and starvation (Cmol/Nmol ratio of 8, 40 and 1, respectively) was evaluated in batch assays. A higher PHA content and biomass growth were achieved in the nutrients presence in comparison to the nutrient starvation condition. The cultures from the SBR treated under short sludge retention time, high organic loading rate, short cycle length (SBR#3) and nutrient excess reached the maximum PHA content (54.9%) and biomass increase (38.9%). Under nutrient limitation, the negative biomass growth was observed under nutrient starvation because of the sampling loss. The succession of microbial communities in SBRs and batch assays was analyzed using terminal restriction fragment length polymorphism. The SBR#3 had the best overall PHA production performance considering its high PHA content and productivity in all nutrient content, it indicates that nitrogen has a substantial impact on PHA yield especially when high organic loading rate enrichment history is involved.

Biohydrogen and polyhydroxyalkanoate production from original hydrolyzed polyacrylamide-containing wastewater

This work aimed to study biohydrogen (H2) and polyhydroxyalkanoate (PHA) production from original hydrolyzed polyacrylamide (HPAM)-containing wastewater. NH4+-N from HPAM hydrolysis was removed efficiently through short-cut nitrification and anoxic ammonia oxidation (anammox). Carbon/Nitrogen (C/N) ratios of effluent reached 51–97, and TOC decreased only 2%–4%, providing potential for subsequent H2 and PHA production. The maximum yields of H2 (0.833 mL·mg−1substrate) and Volatile Fatty Acid (VFA) (465 mg·L−1) occurred at influent C/N ratio of 51. Substrate removal increased linearly with the activities of dehydrogenase and hydrogenase (R2 ≥ 0.990), and H2 yield rose exponentially with enzyme activities (R2 ≥ 0.989). The maximum PHA yield (54.2% VSS) occurred at the 42nd hour and influent C/N ratio of 97. PHA yield was positively correlated with substrate uptake. The change of H2-producing, PHA-accumulating and HPAM-degradating bacteria indicated that those functional microorganisms had synergistic effects on H2 production and substrate uptake, as well as PHA accumulation and substrate uptake.

Scale Up Studies for Polyhydroxyalkanoate Production by a Bacillus flexus Strain with Industrial Potential.

Polyhydroxyalkanoates (PHA) are synthesized by bacteria under unfavourable growth conditions like excess of carbon over nitrogen, coupled with oxygen limitation. The PHA polymers of microbial origin are diverse in chemical composition and material properties. A bioprocess for PHA production by indigenously isolated Bacillus flexus MTCC 12841 was devised and optimized at a laboratory fermentor scale. Fermentation strategies that involved modifications in some parameters like aeration, agitation, temperature, nutrient feeding or changes in C:N ratio led to substantial improvement of 59% in PHA production reaching highest concentration of 9.73g/L. Biomass too was enhanced to 15.70g/L equivalent to 126% increase over the optimized shake flask runs. PHA (Yp/s) and biomass (Yx/s) yields were found to be 0.32 and 0.51g/g respectively, indicating good carbon utilization efficiency. The characterization of polymer by GC-MS revealed that the culture produced poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) as a co-polymer. The novelty of the research findings lies in the demonstration of increased production of PHA at lab fermentor level coupled with the identification of the natural ability of the strain to also produce PHBV without any need for exogenous addition of precursors. The fermentation process as well as the strain may be subjected to further optimization to increase the PHA production as well as to increase the % of HVcontent in the co-polymer.

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) production from engineered Ralstonia eutropha using synthetic and anaerobically digested food waste derived volatile fatty acids

Ralstonia eutropha Re2133/pCB81 is able to utilize various volatile fatty acids (VFAs) (acetate, butyrate, lactate, and propionate) for polyhydroxyalkanoates (PHAs) production. Acetate and lactate resulted in poly(3-hydroxybutyrate) P(3HB) production, butyrate in poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) P(3HB-co-3HHx), and propionate in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) P(3-HB-co-3HV). Various biomass yields i.e. (Yx/s, 0.131 ± 0.02 g/g acetate, 0.221 ± 0.02 g/g butyrate, 0.222 ± 0.05 g/g lactate, and 0.225 ± 0.04 g/g propionate) and PHA yields (Yp/s, 0.01 ± 0.001 g/g acetate, 0.11 ± 0.004 g/g butyrate, 0.03 ± 0.001 g/g lactate, and 0.18 ± 0.005 g/g propionate) were observed with the different organic acids. When all the organic acids were mixed together R. eutropha Re2133/pCB81 had the following order of preference; lactate > butyrate > propionate > acetate. A response surface design study showed that in mixtures butyrate is the main organic acid involved in PHA production and acts as a precursor for HHx monomer units to produce copolymer P(3HB-co-3HHx). Food waste ferment (FWF) without any additional nitrogen source and precursors resulted in P(3HB-co-3HHx) accumulation (52 ± 4% w/w with 18.5 ± 3% HHx fraction).

Effect of nutritional supplements on bio-plastics (PHB) production utilizing sugar refinery waste with potential application in food packaging

Polyhydroxyalkanoates (PHAs) are intracellular carbon and energy storage reserve material stored by gram-negative bacteria under nutrient limitation. PHAs are best alternative biodegradable plastics (bio-plastics) due to their resemblance to conventional synthetic plastic. The present study investigated the synergistic effect of nutritional supplements (amino acid and vitamin) on the PHA production by Alcaligenes sp. NCIM 5085 utilizing a sugar refinery waste (cane molasses) under submerged fermentation process. Initially, the effect of individual factor on PHA yield was studied by supplementing amino acids (cysteine, isoleucine, and methionine), vitamin (thiamin), and cane molasses at varying concentration in the production medium. Further, the cultivation medium was optimized by varying the levels of cane molasses, methionine and thiamin using response surface methodology to enhance the PHA yield. The maximum PHA yield of 70.89% was obtained under the optimized condition, which was then scaled up on 7.5 L-bioreactor. Batch cultivation in 7.5 L-bioreactor under the optimized condition gave a maximum PHA yield and productivity of 79.26% and 0.312 gL−1 h−1, respectively. The PHA produced was subsequently characterized as PHB by FTIR. PHB extracted was of relatively high molecular weight and crystallinity index. DSC analysis gave Tg, Tm, and Xc of 4.2, 179 °C and 66%, respectively. TGA analysis showed thermal stability with maximized degradation occurring at 302 °C, which is above the melting temperature (179 °C) of the purified polymer. The extracted polymer, therefore, possessed desirable material properties to be used in food packaging.

Interactive effect of crude glycerin concentration and C:N ratio on polyhydroxyalkanoates accumulation by mixed microbial cultures modelled with Response Surface Methodology

Response Surface Methodology (RSM) was used to investigate how the crude glycerin concentration and the carbon to nitrogen (C:N) ratio in the culture medium affect four indicators of polyhydroxyalkanoates (PHAs) accumulation by mixed microbial cultures (MMC): the observed coefficient of active-biomass yield (Yobs,BA), the observed coefficient of PHA yield (Yobs,PHA), the PHA content in biomass (XPHA) and the volumetric productivity (PrV). The C:N ratio had the largest effect on Yobs,BA and Yobs,PHA. When the C:N ratio was increased, Yobs,BA decreased and Yobs,PHA increased, regardless of the concentration of crude glycerin in the culture medium. The C:N ratio also had the largest effect on the PHA content, whereas volumetric productivity was strongly affected by both the C:N ratio and the crude glycerin concentration. The optimal conditions for PHA accumulation were a crude glycerin concentration of 8954 mg COD/L with a C:N ratio of 15.9 mg C/mg N-NH4, which gave a Yobs,BA of 0.29 mg CODBA/mg COD, a Yobs,PHA of 0.28 mg CODPHA/mg COD, a XPHA of 55.6% VSS and a PrV of 757.3 mg CODPHA/L⋅d (550.0 mg PHA/L⋅d). The accumulated PHAs consisted mainly of 3-hydroxybutyrate. By using RSM, it was possible to predict crude glycerin concentrations and C:N ratios not tested here that will allow desirable values of PHA content in biomass or PHA productivity, which can be useful for designing PHA production with MMC.

Production and characterization of PHB-HV copolymer by Bacillus thuringiensis isolated from Eisenia foetida.

Polyhydroxyalkanoates (PHAs) are one of the most important biopolyesters produced by vast number of microorganisms that exist in the environment. PHAs gained much attention due to its inherent biodegradable and biocompatible ability along with its physicochemical properties, which are similar to those of conventional petroleum-based plastics. In the present study, PHA producing bacterial strains was isolated from earthworm. Initially, four bacterial strains were selected based on the intensity of fluorescence from 80 non-clonal isolates. Bacillus thuringiensis (B.t.) E101 was identified as the bacterium producing highest yield of PHA (3.6±0.04gL-1 ) through biochemical and molecular techniques such as 16S rRNA gene sequence analysis. Growth parameters such as carbon, nitrogen sources, and incubation time were optimized with respect to higher PHA production. Both qualitative (Fourier transform infrared spectroscopy and nuclear magnetic resonance) and quantitative (GC-MS) characterizations revealed that the polymer produced by B.t.E101 contains the characteristic peaks for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer. This is the first report for the occurrence, successful isolation, and characterization of PHA producing Bacillus sp. from earthworm.

Effect of Carbon Sources on the Accumulation of Endogenous Polymers and Denitritation in the O/A-F/F Mode

To accumulate endogenous polymers during the aerobic phase, the aerobic/anoxic-feast/famine (O/A-F/F) selection mode can be used. It can also be used in situ for endogenous denitrification by activated sludge during the anoxic phase. To further explore the effect of carbon sources on the activated sludge accumulation of endogenous polymers and endogenous denitrification, this study used acetic and glucose as the main carbon sources to investigate the accumulation of endogenous polymers, endogenous denitrification, and the structure and function of enriched activated sludge. The results show that acetic (Ac-SBR) and glucose (Gc-SBR) as the main carbon source systems achieved a 40 mg·L-1 nitrate removal by endogenous denitrification when the influent chemical oxygen demand (COD) was~500 mg·L-1 in the O/A-F/F selection mode. Both the Ac-SBR and Gc-SBR achieved partial denitrification, but the nitrite accumulation of the Ac-SBR was higher than that of the Gc-SBR. Acetic is favorable for the accumulation of endogenous polyhydroxyalkanoate (PHA); PHA drives the endogenous denitrification. The yield of PHA was 0.52 and the denitrification rate (DNR) was 9.65 mg·(L·h)-1. The Gc-SBR system achieved the simultaneous accumulation of PHA and glycogen (Gly). The yield of Gly was higher than that of PHA and the DNR driven by Gly was 4.35 mg·(L·h)-1. The Gly was the main driving force to achieve endogenous denitrification and contributed to 77% of the total nitrogen removal. The 16S rRNA high-throughput sequencing analysis of activated sludge flora shows that the class of β-Proteobacteria in the Proteobacteria was dominant, with an abundance of 40.56% in the Ac-SBR. However, the abundance of β-Proteobacteria was only 18.05% in the Gc-SBR. The class of α-Proteobacteria contributes to glycogen accumulation in the Gc-SBR. The PHA can be accumulated by β-Proteobacteria, Unclassified Bacteroidetes, and Lgnavibacteria in the Ac-SBR.

Polyhydroxyalkanoate production from statistically optimized media using rice mill effluent as sustainable substrate with an analysis on the biopolymer's degradation potential

The present study focuses on the optimization of the bioprocess for the fermentative production of polyhydroxyalkanoate (PHA) by Acinetobacter junii BP 25 using rice mill effluent as a cheap substrate, henceforth to develop an economically feasible biopolymer production process. Statistical tools like Plackett-Burman design (PBD) and Response Surface Methodology (RSM) were used to evaluate the important variables that influence the yield of PHA. Initially from PBD three factors (glycerol, KH2PO4 and incubation time) were taken for further optimization using Box-Behnken design where, the interaction between each of the factors were studied in detail, providing a final optimized media for the high concentration of PHA. Before the optimization process the concentration of PHA was 0.52 ± 0.05 g/l for 1.07 ± 0.32 g/l cell dry mass (CDM) after which a 5.84 fold increase in PHA concentration was observed with 3.04 g/l of PHA. Biodegradation studies of the produced PHA sheets were investigated briefly in both terrestrial and aquatic ecosystem, showing degradation within 8 weeks in soil and 4 weeks in water which was very promising, as the non-degrading property of the conventional plastic have made scientist to research on biopolymers mainly.

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.