A statistical approach for optimization of polyhydroxybutyrate production by marine Bacillus subtilis MSBN17

Production and characterization of polyhydroxybutyrate bioplastic precursor from Parageobacillus toebii using low-cost substrates and its potential antiviral activity

There is an increasing desire for bioplastics produced from renewable resources as an alternative to their petrochemical counterparts. These biopolymers have long-unnoticed antiviral properties. This study aimed to produce and characterize bioplastics by Parageobacillus toebii using low-cost substrates and determine their antiviral activity against coxsackievirus B4. Seven low-cost substrates (bagasse, water hyacinth, rice straw, rice water, sesame husks, molasses, and corn syrup) were compared with glucose for bioplastic precursor production. The highest bioplastic produced was from water hyacinth and glucose, followed by molasses, rice straw, rice water, sesame husks, and bagasse. Water hyacinth and glucose media were further optimized to increase the bioplastic precursor yield. The optimization of the media leads to increases in bioplastic precursor yields of 1.8-fold (3.456 g/L) and 1.496-fold (2.768 g/L), respectively. These bioplastics were further characterized by thermogravimetric analysis (TGA), Fourier-transformed infrared (FTIR) spectroscopy, proton nuclear magnetic resonance (1H NMR), and gas chromatography-mass spectrometry (GC-MS). They are thermostable, and their characterizations confirm the presence of polyhydroxybutyrate. The antiviral assay showed reasonable antiviral effects for bioplastics from water hyacinth (80.33 %) and glucose (55.47 %) media at 250 μg/mL maximum non-toxic concentrations (MNTC). The present investigation demonstrates a low-cost model for producing polyhydroxybutyrate bioplastic precursor for antiviral applications.

Physicochemical cell disruption of Bacillus sp. for recovery of polyhydroxyalkanoates: future bioplastic for sustainability

Polyhydroxybutyrate (PHB) is known for wide applications, biocompatibility, and degradability; however, it cannot be commercialized due to conventional recovery using solvents. The present study employed mechanical cell-disruption methods, such as Pestle and mortar, sonication, and glass bead vortexing, for solvent-free extraction of PHA from Bacillus sp. Different time intervals were set for grinding (5, 10, 15 min), sonicating (1, 3 and 5 min), and vortexing (2, 5 and 8 g glass beads with 5, 10 and 15 min each) hence studying their effect on cell lysis to release PHA. Tris buffer containing phenylmethyl sulfonyl fluoride (PMSF) (20 mM Tris-HCl, pH 8.0, 1 mM PMSF) was employed as a lysis buffer to study its action over Bacillus cells. Its presence was checked with the above methods in cell lysis. Sonicating cells for 5 min in the presence of lysis buffer achieved a maximum PHA yield of 45%. Cell lysis using lysis buffer yielded 35% PHA when vortexing with 5 g glass beads for 15 min. Grinding cells for 15 min showed a maximum yield of 34% but lacked a lysis buffer. The overall results indicated that the action of lysis buffer and physical extraction methods improved PHA yield by %. Therefore, the study sought to evaluate the feasibility of applying laboratory methods for cell disruption. These methods can showcase possible opportunities in large-scale applications. The polymer yield results were compared with standard sodium hypochlorite extraction. Confirmation of obtained polymers as polyhydroxy butyrate (PHB) was made through FTIR and 1HNMR characterization.

Sustainable biorefining and bioprocessing of green seaweed (Ulva spp.) for the production of edible (ulvan) and non-edible (polyhydroxyalkanoate) biopolymeric films

A sustainable biorefining and bioprocessing strategy was developed to produce edible-ulvan films and non-edible polyhydroxybutyrate films. The preparation of edible-ulvan films by crosslinking and plasticisation of ulvan with citric acid and xylitol was investigated using Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) analysis. The edible ulvan film was tested for its gut-friendliness using Lactobacillus and Bifidobacterium spp. (yoghurt) and was shown to improve these gut-friendly microbiome's growth and simultaneously retarding the activity of pathogens like Escherchia coli and Staphylococcus aureus. Green macroalgal biomass refused after the extraction of ulvan was biologically processed by dark fermentation to produce a maximum of 3.48 (± 0.14) g/L of volatile fatty acids (VFAs). Aerobic processing of these VFAs using Cupriavidus necator cells produced 1.59 (± 0.12) g/L of biomass with 18.2 wt% polyhydroxybutyrate. The present study demonstrated the possibility of producing edible and non-edible packaging films using green macroalgal biomass as the sustainable feedstock.

Polyhydroxy butyrate biosynthesis by Azotobacter chroococcum MTCC 3858 through groundnut shell as lignocellulosic feedstock using resource surface methodology

This work appraises the prospect of utilising groundnut shell hydrolysate as a feedstock used for PHB biosynthesis by Azotobacter chroococcum MTCC 3853 under SMF conditions. Sugar reduction: untreated and pretreated 20% H₂SO₄ (39.46 g/l and 62.96 g/l, respectively), untreated and enzymatic hydrolysis (142.35 mg/g and 568.94 mg/g). The RSM-CCD optimization method was used to generate augment PHB biosynthesis from groundnut shell hydrolysate (30 g/l), ammonium sulphate (1.5 g/l), ammonium chloride (1.5 g/l), peptone (1.5 g/l), pH 7, 30 °C, and a 48 h incubation time. The most convincing factors (p < 0.0001), coefficient R² values of biomass 0.9110 and PHB yield 0.9261, PHB production, highest biomass (17.23 g/l), PHB Yield(11.46 g/l), and 66.51 (wt% DCW) values were recorded. The control (untreated GN) PHB yield value of 2.86 g/l increased up to fourfold in pretreated GN. TGA results in a melting range in the peak perceived at 270.55 °C and a DSC peak range of 172.17 °C, correspondingly. According to the results, it furnishes an efficient agricultural waste executive approach by diminishing the production expenditure. It reinforces the production of PHB, thereby shrinking our reliance on fossil fuel-based plastics.

Lipid-membranes interaction, structural assessment, and sustainable production of polyhydroxyalkanoate by Priestia filamentosa AZU-A6 from sugarcane molasses

This study presented for the first time the PHA-lipid interactions by circular dichroism (CD) spectroscopy, besides a sustainable PHA production strategy using a cost-effective microbial isolate. About 48 bacterial isolates were selected from multifarious Egyptian sites and screened for PHAs production. The Fe(AZU-A6) was the most potent isolate, and identified genetically as Priestia filamentosa AZU-A6, while the intracellular PHA granules were visualized by TEM. Sugarcane molasses (SCM) was used an inexpensive carbon source and the production conditions were optimized through a Factor-By-Factor strategy and a Plackett-Burman statistical model. The highest production (6.84 g L^-1) was achieved at 8.0 % SCM, pH 8.0, 35 °C, 250 rpm, and 0.5 g L^-1 ammonium chloride after 72 h. The complementary physicochemical techniques (e.g., FTIR, NMR, GC-MS, DSC, and TGA) have ascertained the structural identity as poly-3-hydroxybutyrate (P3HB) with a characteristic melting temperature of 174.5 °C. The circular dichroism analysis investigated the existence of interactions between the PHB and the different lipids, particularly 1,2-dimyristoyl-sn-glycero-3-phosphocholine. The ATR technique for the lipid-PHB films suggested that both the hydrophobic and electrostatic forces control the lipid-PHB interactions that might induce changes in the structuration of PHB.

A novel higher polyhydroxybutyrate producer Halomonas halmophila 18H with unique cell factory attributes

For cost-competitive biosynthesis of polyhydroxybutyrate (PHB), the screening of efficient producers and characterization of their genomic potential is fundamental. In this study, 94 newly isolated halophilic strains from Turkish salterns were screened for their polyhydroxyalkanoates (PHAs) biosynthesis capabilities through fermentation. Halomonas halmophila 18H was found to be the highest PHB producer, yielding 63.72 % of its biomass as PHB. The PHB produced by this strain was physically and chemically characterized using various techniques. Its genome was also sequenced and found to be large (6,713,657 bp) and have a GC content of 59.9 %. Halomonas halmophila 18H was also found to have several copies of PHB biosynthesis genes, as well as 20 % more protein-coding genes and 1075 singletons compared to other high PHB producers. These unique genomic features make it a promising cell factory for the simultaneous production of PHAs and other biotechnologically important secondary metabolites.

Polyhydroxybutyrate (PHB)-Based Biodegradable Polymer from Agromyces indicus: Enhanced Production, Characterization, and Optimization

Recently, there has been significant interest in bio-based degradable plastics owing to their potential as a green and sustainable alternative to synthetic plastics due to their biodegradable properties. Polyhydroxybutyrate (PHB) is a biodegradable polymer that is produced by bacteria and archaea as carbon and energy reserves. Due to its rapid degradation in natural environments, it can be considered a biodegradable plastic alternative. In the present study, a dye-based procedure was used to screen PHB-producing bacteria isolated from mangrove soil samples. Among the seven isolates, Agromyces indicus (A. indicus), identified by means of 16S rRNA analysis, accumulated the highest amount of PHB. The extracted polymer was characterized by a UV–Vis spectrophotometer, Fourier-transform infrared (FTIR) spectroscopy, and for the presence of the phbB gene, which confirmed the structure of the polymer as PHB. The maximum PHB production by A. indicus was achieved after 96 h of incubation at a pH of 8.0 and 35 °C in the presence of 2% NaCl, with glucose and peptone as the carbon and nitrogen sources, respectively. The strain was found to be capable of accumulating PHB when various cheap agricultural wastes, such as rice, barley, corn, and wheat bran, were used as the carbon sources. The response surface methodology (RSM) through the central composite design (CCD) for optimizing the PHB synthesis was found to be highly efficient at augmenting the polymer yields. As a result of the optimum conditions obtained from the RSM, this strain can increase the PHB content by approximately 1.4-fold when compared with an unoptimized medium, which would substantially lower the production cost. Therefore, the isolate A. indicus strain B2 may be regarded as one of the best candidates for the industrial production of PHB from agricultural wastes, and it can remove the environmental concerns associated with synthetic plastic.

Production of eco-friendly PHB-based bioplastics by Pseudomonas aeruginosa CWS2020 isolate using poultry (chicken feather) waste

Nowadays, the accumulation of non-degradable plastics and other disposed wastes leads to environmental pollution across the world. The production of eco-friendly and cost-effective poly-β-hydroxybutyrate (PHB) could be a better alternative to conventional petroleum-based plastics and prevent environmental pollution. Besides, the area in and around Namakkal, Tamil Nadu, India is well known for poultries, currently facing the number of environmental issues due to the accumulation of chicken feather waste. This study focused on the production of eco-friendly PHB by recycling poultry (chicken feather) waste as the substrate. The native PHB producers were screened from the chicken waste disposal site in Namakkal by Sudan black B staining method. Further, the potent bacterial isolate was identified as Pseudomonas aeruginosa (NCBI accession MF18889) by phenotypic and genotypic characteristics. The PHB production media with chicken feather waste was statistically optimized by response surface methodology. The dry weight of PHB produced under optimized condition (15.96 g/L chicken feather waste, 37 °C temperature, 19.8 g/L glucose and 6.85 pH) was found to be 4.8 g/L. Besides, PHB was characterized and confirmed by thin-layer chromatography, Fourier-transform infrared spectroscopy and Gas chromatography-mass spectrometry analysis. Thus, this study concludes that poultry waste could be a complex nitrogen source for improving the growth of PHB producers and substantially increasing the yield of PHB, and it will be an eco-friendly and low-cost production in bioprocess technology.

Bacillus cereus saba.zh, a novel bacterial strain for the production of bioplastic (polyhydroxybutyrate)

The identification of novel bacterial strains with a high production potential of polyhydroxybutyrate (PHB) to substitute the bioplastics with non-biodegradable plastics and reducing environmental pollution is really effective. The present study was done with the purpose of PHB bioplastic production using a novel bacterial strain. Twenty-one different bacterial isolates were obtained from petrochemical wastewater, which among them, 10 isolates were PHB positive. The presence of PHB granules was detected in the isolates using Sudan Black B staining. The most excellent PHB-accumulating bacterium with a maximum yield of PHB (61.53%) was selected and identified as Bacillus cereus saba.zh, based on morphological, biochemical, and molecular techniques. 16S rRNA nucleotide sequence of the bacterium was assigned accession number: MT975245 in the NCBI database. The phylogenetic tree data showed that the closest type strain to the Bacillus cereus saba.zh is the Bacillus cereus SDB4 (91%). The three genes (phaA, phaB, and phaC) responsible for the PHB biosynthesis were amplified using the specific oligonucleotide primers by PCR technique. The highest PHB yield was achieved when the culture medium was supplemented with 3% sugarcane molasses as a carbon source, ammonium sulfate as the nitrogen source, at pH 7, and temperature of 30 °C. The characterization of the extracted polymer by FTIR and ¹H NMR spectroscopy proves the presence of methyl, methylene, methine, hydroxyl, and ester carbonyl groups and confirmed the structure of biopolymer as PHB. The novel strain Bacillus cereus saba.zh has good potential as an appropriate candidate for low-cost industrial production of bioplastic.

Emergent Approaches to Efficient and Sustainable Polyhydroxyalkanoate Production

Petroleum-derived plastics dominate currently used plastic materials. These plastics are derived from finite fossil carbon sources and were not designed for recycling or biodegradation. With the ever-increasing quantities of plastic wastes entering landfills and polluting our environment, there is an urgent need for fundamental change. One component to that change is developing cost-effective plastics derived from readily renewable resources that offer chemical or biological recycling and can be designed to have properties that not only allow the replacement of current plastics but also offer new application opportunities. Polyhydroxyalkanoates (PHAs) remain a promising candidate for commodity bioplastic production, despite the many decades of efforts by academicians and industrial scientists that have not yet achieved that goal. This article focuses on defining obstacles and solutions to overcome cost-performance metrics that are not sufficiently competitive with current commodity thermoplastics. To that end, this review describes various process innovations that build on fed-batch and semi-continuous modes of operation as well as methods that lead to high cell density cultivations. Also, we discuss work to move from costly to lower cost substrates such as lignocellulose-derived hydrolysates, metabolic engineering of organisms that provide higher substrate conversion rates, the potential of halophiles to provide low-cost platforms in non-sterile environments for PHA formation, and work that uses mixed culture strategies to overcome obstacles of using waste substrates. We also describe historical problems and potential solutions to downstream processing for PHA isolation that, along with feedstock costs, have been an Achilles heel towards the realization of cost-efficient processes. Finally, future directions for efficient PHA production and relevant structural variations are discussed.

Biosynthesized Poly(3-Hydroxybutyrate) on Coated Pineapple Leaf Fiber Papers for Biodegradable Packaging Application

This paper is aimed at investigating the usage of biosynthesized poly(3-hydroxybutyrate) (P(3-HB)) for a coating on pineapple leaf fiber paper (PLFP). For this purpose, (P(3-HB)) was produced by Rhodococcus pyridinivorans BSRT1-1, a highly potential P(3-HB) producing bacterium, with a weight-average molecular weight (M_w) of 6.07 × 10 ⁻⁵ g/mol. This biosynthesized P(3-HB) at 7.5% (w/v) was then coated on PLFP through the dip-coating technique with chloroform used as a solvent. The respective coated PLFP showed that P(3-HB) could be well coated all over on the PLFP surface as confirmed by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The brightness and mechanical properties of PLFP could be improved by coating with biosynthesized P(3-HB) in comparison to commercially available P(3-HB) and non-coated PLFP. Furthermore, coating of P(3-HB) significantly increased the water drop penetration time on the surface of PLFP and was similar to that of the commercial P(3-HB) with the same content. The results showed that all the coated PLPF samples can be degraded under the soil burial test conditions. We have demonstrated that the P(3-HB) coated PLFP paper has the ability to prevent water drop penetration and could undergo biodegradation. Taken together, the P(3-HB) coated PLFP can be applied as a promising biodegradable paper packaging.

Bacillus subtilis as a robust host for biochemical production utilizing biomass

Bacillus subtilis is regarded as a suitable host for biochemical production owing to its excellent growth and bioresource utilization characteristics. In addition, the distinct endogenous metabolic pathways and the suitability of the heterologous pathways have made B. subtilis a robust and promising host for producing biochemicals, such as: bioalcohols; bioorganic acids (lactic acids, α-ketoglutaric acid, and γ-aminobutyric acid); biopolymers (poly(γ-glutamic acid, polyhydroxyalkanoates (PHA), and polysaccharides and monosaccharides (N-acetylglucosamine, xylooligosaccharides, and hyaluronic acid)); and bioflocculants. Also for producing oligopeptides and functional peptides, owing to its efficient protein secretion system. Several metabolic and genetic engineering techniques, such as target gene overexpression and inactivation of bypass pathways, have led to the improvement in production titers and product selectivity. In this review article, recent progress in the utilization of robust B. subtilis-based host systems for biomass conversion and biochemical production has been highlighted, and the prospects of such host systems are suggested.

Production and characterization of exopolysaccharide from the sponge-associated Bacillus subtilis MKU SERB2 and its in-vitro biological properties

In this study, the sponge-associated a potential endosymbiotic bacterium, Bacillus subtilis MKU SERB2 was identified and optimized the production of exopolysaccharide (EPS) by using response surface methodology (RSM). The central composite rotatable design (CCRD) exhibited the highest yield of EPS (617.81 μg/mL) obtained from the optimized medium containing 11.5 g/L of sucrose, 3.5 g/L of yeast extract, 3.0 g/L of peptone, and 2.5 g/L of calcium chloride. Fourier transform infrared (FTIR) spectrum of purified EPS indicated that the presence of carboxyl, hydroxyl, and amide as functional groups, and their structural composition was confirmed by ¹H and ¹³C nuclear magnetic resonance (NMR) analysis. Moreover, the fibrous, porous and semi-crystalline nature of EPS was confirmed by SEM and X-ray powder diffraction (XRD) analysis and the EDX inferred demonstrated the presence of C, Na, O, N, S, and Cl respectively. Further, the isolated EPS exhibited potent antioxidant activity and moderate anticoagulant efficacy whereas there was no hemolytic and lymphocytes toxicity. Overall, our result suggests that the functional and biological properties of the EPS imply the potential applications in food and pharmaceutical industries in the future.

Screening of polyhydroxybutyrate producing indigenous bacteria from polluted lake soil

The prime aim of this study was to enumerate predominant bacteria from polluted lake soil samples, which possess polyhydroxybutyrate (PHB) fabricating potential and identify the suitable growth conditions and nutritional factors for PHB fabrication. From several numbers of bacterial cultures, one culture has the competence to yield PHB, and it was endorsed through Sudan Black B stain, Nile red staining, SEM analysis, and growth in PHB selective media. Under the microscopic observation, the fluorescent cells and polymeric granules were observed in the fluorescent microscope and SEM, respectively. This PHB fabricating isolate was recognized as Bacillus cereus NDRMN001 through 16S rRNA partial sequence analysis. The structural characteristics of PHB produced by B. cereus NDRMN001 were studied through FT-IR, 1H NMR, and 13C NMR analysis. The peak observed at 1759.27 cm-1 on FT-IR analysis is corresponding to the signal band of PHB. In 1H NMR peaks were noticed at 1.67, 2.37 to 2.71, and 3.38 to 7.68 which corresponding to -CH3, -CH2, and -CH protons of PHB. About 4 notable peaks were noticed in 13C NMR analysis at 19.62, 68.27, 40.68, and 169.11 ppm which appeared close to the carboxyl group of PHB. About 10% of inoculum, pH 7.5, 2 g L of yeast extract, 20 g L of rice bran, 35 °C, and 2 days of incubation were recognized as optimal growth conditions for B. cereus NDRMN001 to produce PHB. The identified B. cereus NDRMN001 has the potential to yield 91.48% of PHB as 33.19 g L of PHB from 36.26 g L of culture biomass. The complete results conclude that the B. cereus NDRMN001 screened from polluted lake soil has the competence to produce fine quality and quantity of PHB in a short duration of fabrication process under favorable conditions with the utilization of cheap nutritional factors.

Microbial Polyhydroxyalkanoates and Nonnatural Polyesters

Microorganisms produce diverse polymers for various purposes such as storing genetic information, energy, and reducing power, and serving as structural materials and scaffolds. Among these polymers, polyhydroxyalkanoates (PHAs) are microbial polyesters synthesized and accumulated intracellularly as a storage material of carbon, energy, and reducing power under unfavorable growth conditions in the presence of excess carbon source. PHAs have attracted considerable attention for their wide range of applications in industrial and medical fields. Since the first discovery of PHA accumulating bacteria about 100 years ago, remarkable advances have been made in the understanding of PHA biosynthesis and metabolic engineering of microorganisms toward developing efficient PHA producers. Recently, nonnatural polyesters have also been synthesized by metabolically engineered microorganisms, which opened a new avenue toward sustainable production of more diverse plastics. Herein, the current state of PHAs and nonnatural polyesters is reviewed, covering mechanisms of microbial polyester biosynthesis, metabolic pathways, and enzymes involved in biosynthesis of short-chain-length PHAs, medium-chain-length PHAs, and nonnatural polyesters, especially 2-hydroxyacid-containing polyesters, metabolic engineering strategies to produce novel polymers and enhance production capabilities and fermentation, and downstream processing strategies for cost-effective production of these microbial polyesters. In addition, the applications of PHAs and prospects are discussed.

Bioplastic (poly-3-hydroxybutyrate) production by the marine bacterium Pseudodonghicola xiamenensis through date syrup valorization and structural assessment of the biopolymer

Biobased degradable plastics have received significant attention owing to their potential application as a green alternative to synthetic plastics. A dye-based procedure was used to screen poly-3-hydroxybutyrate (PHB)-producing marine bacteria isolated from the Red Sea, Saudi Arabia. Among the 56 bacterial isolates, Pseudodonghicola xiamenensis, identified using 16S rRNA gene analyses, accumulated the highest amount of PHB. The highest PHB production by P. xiamenensis was achieved after 96 h of incubation at pH 7.5 and 35 °C in the presence of 4% NaCl, and peptone was the preferred nitrogen source. The use of date syrup at 4% (w/v) resulted in a PHB concentration of 15.54 g/L and a PHB yield of 38.85% of the date syrup, with a productivity rate of 0.162 g/L/h, which could substantially improve the production cost. Structural assessment of the bioplastic by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy revealed the presence of methyl, hydroxyl, methine, methylene, and ester carbonyl groups in the extracted polymer. The derivative products of butanoic acid estimated by gas chromatography-mass spectrometry [butanoic acid, 2-amino-4-(methylseleno), hexanoic acid, 4-methyl-, methyl ester, and hexanedioic acid, monomethyl ester] confirmed the structure of PHB. The present results are the first report on the production of a bioplastic by P. xiamenensis, suggesting that Red Sea habitats are a potential biological reservoir for novel bioplastic-producing bacteria.

Response surface method for polyhydroxybutyrate (PHB) bioplastic accumulation in Bacillus drentensis BP17 using pineapple peel

Polyhydroxybutyrate (PHB) is a biodegradable biopolymer which is useful for various applications including packing, medical and coating materials. An endospore-forming bacterium (strain BP17) was isolated from composted soil and evaluated for PHB production. Strain BP17, taxonomically identified as Bacillus drentensis, showed enhanced PHB accumulation and was selected for further studies. To achieve maximum PHB production, the culture conditions for B. drentensis BP17 were optimized through response surface methodology (RSM) employing central composite rotatable design (CCRD). The final optimum fermentation conditions included: pineapple peel solution, 11.5% (v/v); tryptic soy broth (TSB), 60 g/L; pH, 6.0; inoculum size, 10% (v/v) and temperature, 28°C for 36 h. This optimization yielded 5.55 g/L of PHB compared to the non-optimized condition (0.17 g/L). PHB accumulated by B. drentensis BP17 had a polydispersity value of 1.59 and an average molecular weight of 1.15x105 Da. Thermal analyses revealed that PHB existed as a thermally stable semi-crystalline polymer, exhibiting a thermal degradation temperature of 228°C, a melting temperature of 172°C and an apparent melting enthalpy of fusion of 83.69 J/g. It is evident that B. drentensis strain BP17 is a promising bacterium candidate for PHB production using agricultural waste, such as pineapple peel as a low-cost alternative carbon source for PHB production.

Production and Characterization of Bioplastic by Polyhydroxybutyrate Accumulating Erythrobacter aquimaris Isolated from Mangrove Rhizosphere

The synthesis of bioplastic from marine microbes has a great attendance in the realm of biotechnological applications for sustainable eco-management. This study aims to isolate novel strains of poly-β-hydroxybutyrate (PHB)-producing bacteria from the mangrove rhizosphere, Red Sea, Saudi Arabia, and to characterize the extracted polymer. The efficient marine bacterial isolates were identified by the phylogenetic analysis of the 16S rRNA genes as Tamlana crocina, Bacillus aquimaris, Erythrobacter aquimaris, and Halomonas halophila. The optimization of PHB accumulation by E. aquimaris was achieved at 120 h, pH 8.0, 35 °C, and 2% NaCl, using glucose and peptone as the best carbon and nitrogen sources at a C:N ratio of 9.2:1. The characterization of the extracted biopolymer by Fourier-transform infrared spectroscopy (FTIR), Nuclear magnetic resonance (NMR), and Gas chromatography-mass spectrometry (GC-MS) proves the presence of hydroxyl, methyl, methylene, methine, and ester carbonyl groups, as well as derivative products of butanoic acid, that confirmed the structure of the polymer as PHB. This is the first report on E. aquimaris as a PHB producer, which promoted the hypothesis that marine rhizospheric bacteria were a new area of research for the production of biopolymers of commercial value.

Enhancement of bioplastic polyhydroxybutyrate P(3HB) production from glucose by newly engineered strain Cupriavidus necator NSDG-GG using response surface methodology

This study aimed to enhance production of polyhydroxybutyrate P(3HB) by a newly engineered strain of Cupriavidus necator NSDG-GG by applying response surface methodology (RSM). From initial experiment of one-factor-at-a-time (OFAT), glucose and urea were found to be the most significant substrates as carbon and nitrogen sources, respectively, for the production of P(3HB). OFAT experiment results showed that the maximum biomass, P(3HB) content, and P(3HB) concentration of 8.95 g/L, 76 wt%, and 6.80 g/L were achieved at 25 g/L glucose and 0.54 g/L urea with an agitation rate of 200 rpm at 30 °C after 48 h. In this study, RSM was applied to optimize the three key variables (glucose concentration, urea concentration, and agitation speed) at a time to obtain optimal conditions in a multivariable system. Fermentation experiments were conducted in shaking flask by cultivation of C. necator NSDG-GG using various glucose concentrations (10-50 g/L), urea concentrations (0.27-0.73 g/L), and agitation speeds (150-250 rpm). The interaction between the variables studied was analyzed by ANOVA analysis. The RSM results indicated that the optimum cultivation conditions were 37.70 g/L glucose, 0.73 g/L urea, and 200 rpm agitation speed. The validation experiments under optimum conditions produced the highest biomass of 12.84 g/L, P(3HB) content of 92.16 wt%, and P(3HB) concentration of 11.83 g/L. RSM was found to be an efficient method in enhancing the production of biomass, P(3HB) content, and P(3HB) concentration by 43, 21, and 74%, respectively.

Standardization of biopolymer production from seaweed associative bacteria

Polyhydroxyalkanoate (PHA) is the biodegradable plastic, which is shown the similar properties to the synthetic plastic. Production of PHA is expensive when compared with petrochemical based plastics costs and also hazardous to ecosystem. In order to overcome these drawbacks, some cheaper commercially available carbon sources like rice bran, coconut cake, palm jaggary, etc. can be used. The present study aimed to identify the potential PHA producing bacterial strains from different seaweeds. Based on PHA production and crotonic acid assay, two bacterial strains were screened and designated as M3 and S6 which were found to be efficient PHA producers. Potential PHA producers of M3 and S6 were identified as Bacillus cereus RBL6 and Pseudomonas pseudoalcaligens RBL7 by 16S rRNA gene sequencing. The physical and nutritional parameters such as pH, temperature, incubation period, substrate, carbon and nitrogen concentration have been used for enhancing PHA production which was served as precursor. The purified PHA had been chemically characterized by FT-IR, GC-MS and viewed through SEM.

Antiadhesive activity of poly-hydroxy butyrate biopolymer from a marine Brevibacterium casei MSI04 against shrimp pathogenic vibrios

Background

Vibrio pathogens are causative agents of mid-culture outbreaks, and early mortality syndrome and secondary aetiology of most dreadful viral outbreaks in shrimp aquaculture. Among the pathogenic vibrios group, Vibrio alginolyticus and V. harveyi are considered as the most significant ones in the grow-out ponds of giant black tiger shrimp Penaeus monodon in India. Use of antibiotics was banned in many countries due to the emergence of antibiotic-resistant strains and accumulation of residual antibiotics in harvested shrimp. There is an urgent need to consider the use of alternative antibiotics for the control of vibriosis in shrimp aquaculture. Biofilm formation is a pathogenic and/or establishment mechanism of Vibrio spp. This study aims to develop novel safe antibiofilm and/or antiadhesive process using PHB to contain vibrios outbreaks in shrimp aquaculture.

Results

In this study a poly-hydroxy butyrate (PHB) polymer producing bacterium Brevibacterium casei MSI04 was isolated from a marine sponge Dendrilla nigra and production of PHB was optimized under submerged-fermentation (SmF) conditions. The effect of carbon, nitrogen and mineral sources on PHB production and enhanced production of PHB by response surface methods were demonstrated. The maximum PHB accumulation obtained was 6.74 g/L in the optimized media containing 25 g/L starch as carbon source, 96 h of incubation, 35°C and 3% NaCl. The highest antiadhesive activity upto 96% was recorded against V. vulnificus, and V. fischeri, followed by 92% against V. parahaemolyticus and V. alginolyticus and 88% inhibition was recorded against V. harveyi.

Conclusion

In this study, a thermostable biopolymer was chemically characterized as PHB based on ¹HNMR spectra, FT-IR and GC-MS spectra. The NMR spectra revealed that the polymer was an isocratic homopolymer and it also confirmed that the compound was PHB. The antiadhesive activity of PHB was determined in microtitre plate assay and an effective concentration (EC) of PHB (200 μl containing 0.6 mg PHB) was confirmed by confocal laser scanning microscopic analysis of vibrio biofilm on pre-treated glass and polystyrene surfaces. This is a first report on anti-adhesive activity of PHB against prominent vibrio pathogens in shrimp aquaculture.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-014-0114-3) contains supplementary material, which is available to authorized users.

Optimization of polyhydroxybutyrate production by marine Bacillus megaterium MSBN04 under solid state culture

A marine sponge-associated bacterium Bacillus megaterium MSBN04 was used for the production of polyhydroxybutyrate (PHB) under solid state culture (SSC). A central composite design (CCD) was employed to optimize the production medium and to find out the interactive effects of four independent variables, viz. tapioca industry waste, palm jaggery, horse gram flour and trace element solution on PHB production. The maximum yield of PHB 8.637 mg g(-1) of substrate (tapioca industry waste) was achieved from biomass 15.203 mg g(-1) of substrate, using statistically optimized medium. The horse gram flour (nitrogen source) and trace element solution were found to be critical control factors for PHB synthesis. The (1)H NMR analysis revealed that the polymer was a PHB monomer. PHB obtained from this study having high molecular weight (6.7×10(5) Da) with low polydispersity index (PDI) value (1.71) and produced PHB was used to synthesize PHB polymeric nanoparticles using solvent displacement approach. Therefore, B. megaterium MSBN04 is an ideal candidate that can be exploited biotechnologically for the commercial production of PHB under solid state culture.