Efficient polyhydroxybutyrate production from Bacillus juice substrate thuringiensis using sugarcane

Valorization of Sugarcane Bagasse for Co-Production of Poly(3-hydroxybutyrate) and Bacteriocin Using Bacillus cereus Strain S356

Poly(3-hydroxybutyrate) (P(3HB)) is an attractive biodegradable plastic alternative to petroleum-based plastic. However, the cost of microbial-based bioplastic production mainly lies in the cultivation medium. In this study, we screened the isolates capable of synthesizing P(3HB) using sugarcane bagasse (SCB) waste as a carbon source from 79 Bacillus isolates that had previously shown P(3HB) production using a commercial medium. The results revealed that isolate S356, identified as Bacillus cereus using 16S rDNA and gyrB gene analysis, had the highest P(3HB) accumulation. The highest P(3HB) yield (5.16 g/L, 85.3% of dry cell weight) was achieved by cultivating B. cereus S356 in an optimal medium with 1.5% total reducing sugar with SCB hydrolysate as the carbon source and 0.25% yeast extract as the nitrogen source. Transmission electron microscopy analysis showed the accumulation of approximately 3-5 P(3HB) granules in each B. cereus S356 cell. Proton nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy analyses confirmed that the polymer extracted from B. cereus S356 was P(3HB). Notably, during cultivation for P(3HB) plastic production, B. cereus S356 also secreted bacteriocin, which had high antibacterial activity against the same species (Bacillus cereus). Overall, this work demonstrated the possibility of co-producing eco-friendly biodegradable plastic P(3HB) and bacteriocin from renewable resources using the potential of B. cereus S356.

Preparation, characterization and evaluation of HPβCD-PTX/PHB nanoparticles for pH-responsive, cytotoxic and apoptotic properties

Paclitaxel (PTX) is a potent anticancer drug. However, PTX exhibits extremely poor solubility in aqueous solution along with severe side effects. Therefore, in this study, an inclusion complex was prepared between PTX and hydroxypropyl-β-cyclodextrin (HPβCD) by solvent evaporation to enhance the drug's solubility. The HPβCD-PTX inclusion complex was then encapsulated in poly-3-hydroxybutyrate (PHB) to fabricate drug-loaded nanoparticles (HPβCD-PTX/PHB NPs) by nanoprecipitation. The HPβCD-PTX/PHB NPs depicted a higher release of PTX at pH 5.5 thus demonstrating a pH-dependent release profile. The cytotoxic properties of HPβCD-PTX/PHB NPs were tested against MCF-7, MDA-MB-231 and SW-620 cell lines. The cytotoxic potential of HPβCD-PTX/PHB NPs was 2.59-fold improved in MCF-7 cells in comparison to free PTX. Additionally, the HPβCD-PTX/PHB NPs improved the antimitotic (1.68-fold) and apoptotic (8.45-fold) effects of PTX in MCF-7 cells in comparison to PTX alone. In summary, these pH-responsive nanoparticles could be prospective carriers for enhancing the cytotoxic properties of PTX for the treatment of breast cancer.

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.

Traditional Chinese medicine residue enzymatic hydrolysates for production of polyhydroxyalkanoate by newly isolated Bacillus altitudinis

Traditional Chinese medicine residue (TCMR) was utilized as an inexpensive carbon source for the production of poly(3-hydroxybutyrate) (PHB) using the newly isolated Bacillus altitudinis HBU-SI7. The results showed that Yu Ping Feng TCMR could be directly hydrolysed by cellulase to obtain a high proportion of glucose (99 % of total sugar) without pretreatment, achieving an enzymatic hydrolysis rate of up to 89.2 %. B. altitudinis could grow and produce PHB when using enzymatically hydrolysed TCMR in a 5-L fermenter. After 20 h of fermentation, the maximum concentration of PHB was 11.2 g/L, and the highest cell dry weight (CDW) was 15.4 g/L, with 72.7 % of the PHB fraction in CDW. Moreover, this strain could utilize enzymatic hydrolysates from various herbal formulas to produce high levels of PHB. This novel approach aims to accumulate PHB from TCMR hydrolysates, offering an effective and environmentally friendly method to reduce production costs and achieve mass production.

Poly(3-hydroxybutyrate) Production from Lignocellulosic Wastes Using Bacillus megaterium ATCC 14581

This study aimed to analyze the production of poly(3-hydroxybutyrate) (PHB) from lignocellulosic biomass through a series of steps, including microwave irradiation, ammonia delignification, enzymatic hydrolysis, and fermentation, using the Bacillus megaterium ATCC 14581 strain. The lignocellulosic biomass was first pretreated using microwave irradiation at different temperatures (180, 200, and 220 °C) for 10, 20, and 30 min. The optimal pretreatment conditions were determined using the central composite design (CCD) and the response surface methodology (RSM). In the second step, the pretreated biomass was subjected to ammonia delignification, followed by enzymatic hydrolysis. The yield obtained for the pretreated and enzymatically hydrolyzed biomass was lower (70.2%) compared to the pretreated, delignified, and enzymatically hydrolyzed biomass (91.4%). These hydrolysates were used as carbon substrates for the synthesis of PHB using Bacillus megaterium ATCC 14581 in batch cultures. Various analytical methods were employed, namely nuclear magnetic resonance (1H-NMR and13C-NMR), electrospray ionization mass spectrometry (EI-MS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA), to identify and characterize the extracted PHB. The XRD analysis confirmed the partially crystalline nature of PHB.

A Novel Sphingomonas sp. Isolated from Argan Soil for the Polyhydroxybutyrate Production from Argan Seeds Waste

Polyhydroxybutyrate (PHB) is a biodegradable bio-based polymer synthesized by microorganisms under unfavorable conditions from agro-industrial residues as a source of carbon. These aspects make the bio-based polymer attractive for the mass production of biodegradable plastics, and a definitive replacement for petroleum-based plastics. The aim of this work was to characterize the putative PHB-producing bacterium 1B isolated from the argan soil, to identify the polymer produced, and quantify the PHB production using argan seeds waste. DNA extraction, PCR, and Sanger sequencing were conducted for the molecular identification of strain 1B; the residual biomass and the PHB quantification were measured and compared in the presence of simple sugars and pretreated argan seeds waste. The 1B growth and PHB synthesis were optimized by selecting physical and nutritional parameters: temperature, incubation time, pH, NaCl concentration, and nitrogen sources concentrations. A preliminary characterization of the bio-based polymer extracted was conducted by UV-Visible spectrophotometry and FTIR analysis. The strain 1B was identified as belonging to the genus Sphingomonas. The PHB final yield was higher in a growth culture enriched with argan waste (3.06%) than with simple sugars. The selected conditions for the bacterial optimal growth incremented the PHB final yield to 6.13%, while the increase in the argan residue concentration from 1 to 3% in a larger culture volume led to the PHB final yield of 8.16%. UV-Visible spectrophotometry of the extracted sample reported a remarkable peak at 248 nm, as well as FTIR spectra analysis, showed peaks at 1728 and 1282 wavenumber/cm. Both preliminary characterizations demonstrated that the extracted sample is the bio-based polymer polyhydroxybutyrate. The results reported in this work reveal how the costless available argan seeds can be used for polyhydroxybutyrate production using a novel Sphingomonas species.

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.

Microbial cell factories for the production of polyhydroxyalkanoates

Pollution caused by persistent petro-plastics is the most pressing problem currently, with 8 million tons of plastic waste dumped annually in the oceans. Plastic waste management is not systematized in many countries, because it is laborious and expensive with secondary pollution hazards. Bioplastics, synthesized by microorganisms, are viable alternatives to petrochemical-based thermoplastics due to their biodegradable nature. Polyhydroxyalkanoates (PHAs) are a structurally and functionally diverse group of storage polymers synthesized by many microorganisms, including bacteria and Archaea. Some of the most important PHA accumulating bacteria include Cupriavidus necator, Burkholderia sacchari, Pseudomonas sp., Bacillus sp., recombinant Escherichia coli, and certain halophilic extremophiles. PHAs are synthesized by specialized PHA polymerases with assorted monomers derived from the cellular metabolite pool. In the natural cycle of cellular growth, PHAs are depolymerized by the native host for carbon and energy. The presence of these microbial PHA depolymerases in natural niches is responsible for the degradation of bioplastics. Polyhydroxybutyrate (PHB) is the most common PHA with desirable thermoplastic-like properties. PHAs have widespread applications in various industries including biomedicine, fine chemicals production, drug delivery, packaging, and agriculture. This review provides the updated knowledge on the metabolic pathways for PHAs synthesis in bacteria, and the major microbial hosts for PHAs production. Yeasts are presented as a potential candidate for industrial PHAs production, with their high amenability to genetic engineering and the availability of industrial-scale technology. The major bottlenecks in the commercialization of PHAs as an alternative for plastics and future perspectives are also critically discussed.

Production of polyhydroxyalkanoates (PHAs) by Bacillus megaterium using food waste acidogenic fermentation-derived volatile fatty acids

High production costs still hamper fast expansion of commercial production of polyhydroxyalkanoates (PHAs). This problem is greatly related to the cultivation medium which accounts for up to 50% of the whole process costs. The aim of this research work was to evaluate the potential of using volatile fatty acids (VFAs), derived from acidogenic fermentation of food waste, as inexpensive carbon sources for the production of PHAs through bacterial cultivation. Bacillus megaterium could assimilate glucose, acetic acid, butyric acid, and caproic acid as single carbon sources in synthetic medium with maximum PHAs production yields of 9-11%, on a cell dry weight basis. Single carbon sources were then replaced by a mixture of synthetic VFAs and by a VFAs-rich stream from the acidogenic fermentation of food waste. After 72 h of cultivation, the VFAs were almost fully consumed by the bacterium in both media and PHAs production yields of 9-10%, on cell dry weight basis, were obtained. The usage of VFAs mixture was found to be beneficial for the bacterial growth that tackled the inhibition of propionic acid, iso-butyric acid, and valeric acid when these volatile fatty acids were used as single carbon sources. The extracted PHAs were revealed to be polyhydroxybutyrate (PHB) by characterization methods of Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The obtained results proved the possibility of using VFAs from acidogenic fermentation of food waste as a cheap substrate to reduce the cost of PHAs production.

Isolation of Two Bacterial Species from Argan Soil in Morocco Associated with Polyhydroxybutyrate (PHB) Accumulation: Current Potential and Future Prospects for the Bio-Based Polymer Production

The environmental issues caused by the impacts of synthetic plastics use and derived wastes are arising the attention to bio-based plastics, natural polymers produced from renewable resources, including agricultural, industrial, and domestic wastes. Bio-based plastics represent a potential alternative to petroleum-based materials, due to the insufficient availability of fossil resources in the future and the affordable low cost of renewable ones that might be consumed for the biopolymer synthesis. Among the polyhydroxyalkanoates (PHA), the polyhydroxybutyrate (PHB) biopolymer has been synthesized and characterized with great interest due to its wide range of industrial applications. Currently, a wide number of bacterial species from soil, activated sludge, wastewater, industrial wastes, and compost have been identified as PHB producers. This work has the purpose of isolating and characterizing PHB-producing bacteria from the agricultural soil samples of Argania spinosa in the south region of Morocco where the plant species is endemic and preserved. During this research, four heat-resistant bacterial strains have been isolated. Among them, two species have been identified as endospore forming bacteria following the Schaffer-Fulton staining method with Malachite green and the Methylene blue method. Black intracellular granules have been appreciated in microscopy at 100× for both strains after staining with Sudan black B. The morphological and biochemical analyses of the isolates, including sugar fermentation and antibiotic susceptibility tests, preliminarily identified the strains 1B and 2D1 belonging to the genus Serratia and Proteus, respectively.

Optimization of cultivation medium and cyclic fed-batch fermentation strategy for enhanced polyhydroxyalkanoate production by Bacillus thuringiensis using a glucose-rich hydrolyzate

The accumulation of petrochemical plastic waste is detrimental to the environment. Polyhydroxyalkanoates (PHAs) are bacterial-derived polymers utilized for the production of bioplastics. PHA-plastics exhibit mechanical and thermal properties similar to conventional plastics. However, high production cost and obtaining high PHA yield and productivity impedes the widespread use of bioplastics. This study demonstrates the concept of cyclic fed-batch fermentation (CFBF) for enhanced PHA productivity by Bacillus thuringiensis using a glucose-rich hydrolyzate as the sole carbon source. The statistically optimized fermentation conditions used to obtain high cell density biomass (OD600 of 2.4175) were: 8.77 g L-1 yeast extract; 66.63% hydrolyzate (v/v); a fermentation pH of 7.18; and an incubation time of 27.22 h. The CFBF comprised three cycles of 29 h, 52 h, and 65 h, respectively. After the third cyclic event, cell biomass of 20.99 g L-1, PHA concentration of 14.28 g L-1, PHA yield of 68.03%, and PHA productivity of 0.219 g L-1 h-1 was achieved. This cyclic strategy yielded an almost threefold increase in biomass concentration and a fourfold increase in PHA concentration compared with batch fermentation. FTIR spectra of the extracted PHAs display prominent peaks at the wavelengths unique to PHAs. A copolymer was elucidated after the first cyclic event, whereas, after cycles CFBF 2-4, a terpolymer was noted. The PHAs obtained after CFBF cycle 3 have a slightly higher thermal stability compared with commercial PHB. The cyclic events decreased the melting temperature and degree of crystallinity of the PHAs. The approach used in this study demonstrates the possibility of coupling fermentation strategies with hydrolyzate derived from lignocellulosic waste as an alternative feedstock to obtain high cell density biomass and enhanced PHA productivity.