Valorization of agricultural residues for bioplastic production by bacteria isolated from plastic dumpsites: Integrating waste streams into the circular bioeconomy

Polyhydroxybutyrates (PHB) are bio-plastics accumulated by some bacteria living in environments where the carbon source is in excess and other nutrients are limited. The aim of this study was to screen Bacillus subtilis for accumulation of PHB, using potato peel as a carbon source. A total of 100 g of potato peels were processed and analyzed for proximate composition. A total of 25 g from 12 soil samples, including four samples from three different locations, were assayed using microbiological techniques to isolate and characterize B. subtilis. PHB accumulation was determined using Sudan Black B dye, and quantified with a spectrophotometer to identify the best-producing isolates. The production conditions, consisting of pH, NaCl concentrations, and nitrogenous sources were optimized and employed in the PHB production, with the processed peel as the sole carbon source cultured with the best isolates. The PHB was analyzed using Fourier Transform Infrared Spectroscopy (FTIR). The proximate compositions of the carbohydrate and protein in the potato peel were 55.11% and 20.38%, respectively. The occurrence rate of B. subtilis was 58.3% (7/12), with 57.14% (4/7) of these isolates being PHB producers, and 4 of them were the best producers. The optimized conditions were pH 7, 3% NaCl and NH4Cl as the nitrogen source. The PHB yield from the three best producers under the optimized conditions was three times higher. FTIR analysis confirmed the polymer as PHB. Garden soil was the best source for isolating PHB-producing B. subtilis, and potato peels were converted from waste to wealth (PHB) with a moderate yield.

The present study focuses on the improvement of production of Poly Hydroxy Butyrate (PHB) using Bacillus megaterium MTCC 8075. The culture media and conditions were studied critically and was found that the maximum PHB production was attained in the presence of glucose as carbon source at 6% concentration with a yield of 55.0 mg/g cell weight and peptone as nitrogen source with a yield of 17.2mg/g cell weight. The optimum pH was found to be 7(22.8mg/g) and it was also investigated that PHB production was maximum corresponding to a temperature of 35°C (35.46mg/g) and at an incubation time of 72 hours (52.2mg/g). PHB was qualitatively analysed using Sudan Black staining method, extracted using sodium hypochlorite, and quantified using crotonic acid assay in UV spectrophotometer at a wavelength of 235nm. PHB production was carried out in various selected effluents like corn stalk waste and petroleum refinery effluent and corn corb yielded the maximum PHB production of 3.1mg/L. The produced PHB was confirmed using Fourier Transform Infrared (FTIR) analysis and NMR spectroscopic studies. PHB production was further improved using two-stage batch culture studies in which PHB production was compared in various nutrient limited conditions of nitrogen and phosphorous. The thermal properties of PHB was studied using Differential Scanning Calorimetry(DSC) and Thermogravimetric Analysis (TGA).

Polyhydroxybutyrate (PHB) bioplastic characterization from the isolate Pseudomonas stutzeri PSB1 synthesized using potato peel feedstock to combat solid waste management

Sustainable autotrophic production of polyhydroxybutyrate (PHB) from CO2 using a two-stage cultivation system

Production of polyhydroxybutyrate (PHB), a biodegradable polymer from seaweed biomass using novel bacterial isolates

Objectives: To isolate and screen the poly hydroxybutyrate (PHB) producing bacteria from Jeppiaar Salt Pane, Chennai. Methods: In the present study the salt pane bacteria were isolated by the serial dilution method using nutrient agar containing 5% NaCl. The potential PHB producers were identified by both Nile blue staining and viable colony screening methods. The PHB production was checked and was extracted by following sodium hypochlorite-chloroform method. The PHB production capability was compared between the two isolates by estimate the percentage of PHB production. Results: Twenty morphologically different bacteria were isolated from a sample collected from Jeppiaar Salt Pane, Chennai. Three potential PHB producers were identified by both Nile blue staining and viable colony screening methods. The isolate AJ11, AJ10, AJ8 were produced 0.225, 0.210, 0.125g/100ml of PHB respectively. The percentage of PHB production was high for the isolate AJ11 (81.8%), AJ10 (72.4%) and minimum production observed for the isolate AJ8 was (43.7%). Conclusion: This screening study for the PHB producers from the salt pane water sample harbouring more suitable isolates with efficient PHB production, the application of PHB in different fields has to be studied further.

Biodegradable polymers represent a hot topic in current environment. Biodegradable polymers can be decomposed into simple molecules like CO2, CH4, H2O and residual biomass. Bacillus sp. KUMBNGBT-64a, isolated from leftover soil that was gathered at Sagar taluk located in Shivamogga, Karnataka, India, was identified as Bacillus tequilensis KUMBNGBT-64a. Phenotypic and genotypic characteristics were used to identify the bacteria. Various conditions were employed to maximize the highest production of PHB by the bacteria. The bacterial isolate was grown on affordable agro-industrial wastes to lower production cost and scale up PHB production. The quantity of PHB contained in the isolated bacterial cells was measured using bio-spectrophotometric analysis. Bacillus sp. KUMBNGBT-64a, a gram positive, motile and spore forming bacterium, was confirmed as Bacillus tequilensis KUMBNGBT-64a by using 16S r-RNA sequence and deposited to GenBank, NCBI. Consent No. PV124813. Additionally, the following conditions of nutritional broth medium, a 72-h incubation period, 37°C temperature, pH 7.0, glucose as a carbon source, ammonium chloride as a nitrogen source, and a 4:1 carbon-nitrogen ratio were shown to be responsible for the greatest generation of PHB. A liquid hydrolysate of feed stock had the highest level of PHB production, and the ʎ-max of 270 nm was used to quantify and validate PHB production. In the present investigation, Bacillus tequilensis KUMBNGBT-64a produced maximum PHB using low cost substrates, which helped to reduce the production cost, and could be used for the large-scale production of the bio plastics.

Polyhydroxyalkanoate (PHA) is a biodegradable material with many potential biomedical applications, including medical implants and drug delivery. This study developed a system for screening production strains in order to optimize PHA production in Cupriavidus taiwanensis 184, 185, 186, 187, 204, 208, 209 and Pseudomona oleovorans ATCC 29347. In this study, Sudan black B staining, Infrared (IR) and Gas Chromatography (GC) analysis indicated that the best strain for PHA synthesis is C. taiwanensis 184, which obtains polyhydroxybutyrate (PHB). Cultivation of C. taiwanensis 184 under a pH of 7.0, at 30 °C, and at an agitation rate of 200 rpm, obtained a PHB content of 10% and PHB production of 0.14 g/L. The carbon and nitrogen types selected for analysis of PHB production by C. taiwanensis 184 were gluconic acid and NH4Cl, respectively. Optimal carbon/nitrogen ratio for PHB production was also determined. This study demonstrated a PHB content of 58.81% and a PHB production of 2.44 g/L when the carbon/nitrogen ratio of 8/1 was selected for C. taiwanensis 184. A two-stage fermentation strategy significantly enhanced PHB content and PHB production. Under a two-stage fermentation strategy with nutrient-limited conditions, C. taiwanensis 184 obtained a PHB content of 72% and a PHB concentration of 7 g/L. Finally, experimental results confirmed that optimizing the growth medium and fermentation conditions for cultivating the indigenous C. taiwanensis 184 strain substantially elevated PHB content from 10% to 72% and PHB production from 0.14 g/L to 7 g/L, respectively.

Background:Poly 3-Hydroxybutyrate (PHB), a class of Poly Hydroxyalkanoates (PHAs), is a group of bacterial storage polymers, produced by various microorganisms in response to nutrient limitation. PHAs are biodegradable polymers which could be a good substitute for current petrochemical plastics. PHB has been synthesized during three enzymatic steps including three genes.Objectives:Our aim was PHB production from recombinant bacteria.Materials and Methods:Ralstonia eutropha was cultured and its genomic DNA was extracted. The phbCAB operon was amplified using designed primers. The fragment was cloned into pET-28a expression vector and then transformed into Escherichia coli BL21. Sudan black staining was used to show the production of PHB.Results:The extracted recombinant plasmid was digested with restriction enzymes. Separation of the desired fragment from the vector was performed to prove the correct insertion of the PCR products into the vector. The colony PCR and sequencing results confirmed the successful transformation. The production of PHB was confirmed by Sudan Black B staining under a light microscope.Conclusions:Various metabolic and fermentation methods have been used in some bacterial strains for PHB production. The use of a recombinant system harboring PHB synthesis genes can produce PHB in higher concentrations compare to natural PHA-producing bacteria. The present study was one of the most important and basic steps of designing a recombinant E. coli that can produce PHB.

Polyhydroxybutyrate (PHB)-Based sustainable bioplastic derived from Bacillus sp. KE4 isolated from kitchen waste effluent

Screening of the strictly xylose-utilizing Bacillus sp. SM01 for polyhydroxybutyrate and its co-culture with Cupriavidus necator NCIMB 11599 for enhanced production of PHB

Background: The global dependency on synthetic plastics has resulted in significant environmental pollution due to their persistence and poor biodegradability. As an alternative, biodegradable bioplastics such as polyhydroxybutyrate (PHB) offer promising eco-friendly solutions. PHB, a bacterial polyester, can be synthesized and extracted from microbial sources using renewable substrates, providing a sustainable option to replace petroleum-derived plastics. Objective: The objective of this study was to isolate PHB-producing bacteria from soil and characterize the extracted PHB both chemically and physically. Methods: Soil samples were collected from the IBGE garden, and a total of 15 bacterial isolates were cultured on nutrient agar. PHB-producing strains were identified using 0.05% Sudan Black B staining, and five isolates showed positive results. These PHB-positive strains were cultivated in PHB production media containing glucose as the carbon source. PHB extraction was performed using sodium hypochlorite and chloroform, and the yield was calculated based on cell dry weight (CDW). Chemical characterization was conducted using Fourier Transform Infrared Spectroscopy (FTIR), and the physical morphology of electrospun PHB nanofibers was analyzed using Scanning Electron Microscopy (SEM). Results: Among all isolates, 5AR yielded the highest PHB production with 0.53 g/L PHB and 1.04 g/L CDW, resulting in a 51.96% yield. Other isolates showed PHB yields as follows: 17AR (31.70%), 27AR (15.09%), 29AR (21.21%), and 45AR (11.76%). FTIR analysis revealed strong absorption peaks at 1723 cm⁻¹, 1720 cm⁻¹, 2946 cm⁻¹, and 1242 cm⁻¹, confirming PHB presence. SEM analysis showed successful fabrication of nanofibers from extracted PHB. Conclusion: This study confirms the potential of soil bacteria in producing PHB and supports their use in bioplastic production. The extracted PHB showed comparable properties to standard PHB, indicating feasibility for eco-friendly applications.

Poly-β-hydroxybutyrate (PHB) is a biodegradable polymer, synthesized as carbon and energy reserve by bacteria and archaea. To the best of our knowledge, this is the first report on PHB production by a rare actinomycete species, Rhodococcus pyridinivorans BSRT1-1. Response surface methodology (RSM) employing central composite design, was applied to enhance PHB production in a flask scale. A maximum yield of 3.6 ± 0.5 g/L in biomass and 43.1 ± 0.5 wt% of dry cell weight (DCW) of PHB were obtained when using RSM optimized medium, which was improved the production of biomass and PHB content by 2.5 and 2.3-fold, respectively. The optimized medium was applied to upscale PHB production in a 10 L stirred-tank bioreactor, maximum biomass of 5.2 ± 0.5 g/L, and PHB content of 46.8 ± 2 wt% DCW were achieved. Furthermore, the FTIR and 1H NMR results confirmed the polymer as PHB. DSC and TGA analysis results revealed the melting, glass transition, and thermal decomposition temperature of 171.8, 4.03, and 288 °C, respectively. In conclusion, RSM can be a promising technique to improve PHB production by a newly isolated strain of R. pyridinivorans BSRT1-1 and the properties of produced PHB possessed similar properties compared to commercial PHB.

The production, recovery, and valorization of polyhydroxybutyrate (PHB) based on circular bioeconomy

Recent progress and challenges in microbial polyhydroxybutyrate (PHB) production from CO2 as a sustainable feedstock: A state-of-the-art review