Isolation and characterization of poly(3-hydroxybutyrate)-producing bacteria from aerobic sludge

Utilization of Noxious Weed Water Hyacinth Biomass as a Potential Feedstock for Biopolymers Production: A Novel Approach

This study aims to utilize a noxious weed water hyacinth biomass (WH) for polyhydroxybutyrate (PHB) production. Alkaline and peracetic acid pretreatment was employed for the hydrolysis of WH and consequently enzymatic saccharification to produce fermentable sugars for PHB production. The pretreatment competence was determined using various operational parameters. By applying ambient conditions, alkaline pretreatment gave higher lignin removal of 65.0%, with 80.8% hydrolysis yield, and on enzyme hydrolysis (40 FPU/g of dry WH), produced total reducing sugar of about 523 mg/g of WH. The resulted WH enzymatic hydolysates were evaluated for the production of PHB by Ralstonia eutropha (ATCC 17699). The WH hydrolysates cultivation was compared to synthetic hydrolysates that contain a similar carbon composition in terms of bacterial growth and PHB synthesis. The effects of various supplements to enhance PHB production were estimated. Supplementation of corn steep liquor (CSL) as a cheap nitrogen source with WH hydrolysates favored a higher amount of PHB synthesis (73%), PHB titer of 7.30 g/L and PHB yield of 0.429 g/g of reducing sugar. Finally, using standard analytical tools, the physical and thermal characteristics of the extracted PHB were evaluated. The findings revealed WH was a promising and technically feasible option for transforming biomass into sustainable biopolymer conversion on a large scale.

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.

Polyhydroxyalkanoate (PHA) biosynthesis from directly valorized ragi husk and sesame oil cake by Bacillus megaterium strain Ti3: Statistical optimization and characterization

Polyhydroxyalkanoates (PHAs) signify the most promising biological substitute to petrochemical plastics. Renewable and inexpensive agro-industrial by-products can be used as potent fermentation feedstocks for sustainable PHA biosynthesis. This study aimed at using a wild type B. megaterium strain Ti3 innate hydrolytic enzyme/s for eco-friendly valorization of 16 lignocellulosic agrowastes to PHA without pretreatments. Initial hydrolytic screening PHA concentration of (0.04-0.17 g/L), highlighted the strain's metabolic versatility. Pareto ranking of Taguchi orthogonal array (TOA) established ragi husk (RH), sesame oil cake (SOC) and KH₂PO₄ as the most influential factors (p < 0.05). The optimized and validated Response surface methodology (RSM) model (R², 0.979; desirability, 1) resulted in 3.8 and 3.6 fold increased PHA production, 4.3 and 3.25 fold increased PHA productivity. A positive correlation (r², 0.5-0.97) was observed amid the producer innate hydrolytic enzymes (lipase, amylase and cellulase) and PHA production. The PHA was characterized by ¹H and ¹³C NMR, GPC, TGA. The polymer was identified as a scl-mcl copolyester with 92% 3HB (3-hydroxybutyrate) and 8% 3HHp (3-hydroxyheptanoate) monomers by NMR. This the first report on B. megaterium self-enzyme reliant non-food agrowastes bioconversion to PHA with 3HHp (3-hydroxyheptanoate) monomers excluding precursor addition, commercial enzymes, pure carbon and nitrogen sources.

Efficient production and characterization of homopolymeric poly(3-hydroxyvalerate) produced by Bacillus strain PJC48

Aliphatic polyester, poly(3-hydroxyvalerate) (PHV), is commonly produced as a granular component in bacterial cells of various species. Based on 16S rDNA gene sequence analysis, strain PJC48 was identified as a Bacillus species. The current study is aimed to screen for a high-yield strain that can produce PHV efficiently and to increase PHV product yield by optimizing the fermentative process. We identified a high-producer strain based on Nile red staining. Characterization of the PHV produced by PJC48 by nuclear magnetic resonance spectroscopy revealed that it consisted of (R)-3-hydroxyvalerate monomers. The suggested model was validated by response surface methodology. Optimization of the PHV yield resulted in an increase of 32.75% compared to control, with a maximum production of 1.64 g/L after 48 H.

Characterization of Polyhydroxyalkanoate Produced by Bacillus megaterium VB89 Isolated from Nisargruna Biogas Plant

Polyhydroxyalkanoates (PHAs) are naturally occurring biodegradable polymers that can curb the extensive use of polypropylene based plastics. In contrast to chemically synthesized polypropylene plastics, PHAs are biodegradable and thus environmentally safe. PHAs have attracted much attention as biocompatible and biodegradable thermoplastics. The present study involves isolation of bacteria from different environments capable of synthesizing PHAs. The bacterium producing highest yield of PHA (0.672 ± 0.041 g/L) was identified as Bacillus megaterium VB89 by biochemical and molecular techniques such as 16S rDNA sequence analysis. Strain VB89 produced polyhydroxybutyrate (PHB) as revealed by FTIR and NMR. This PHB had an average molecular weight of 2.89 × 10⁵ Da and a polydispersity index of 2.37. Thermal properties of the PHB included a glass transition temperature of 13.97 °C, a melting temperature of 181.74 °C, and a decomposition temperature of 234 °C. All these properties indicated that VB89 produced PHB of high purity and good thermal stability.