Synthesis, Characterization, and Structural Properties of Intracellular Copolyester Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Produced byComamonassp. EB 172 from Renewable Resource

Polyhydroxyalkanoate production from rice straw hydrolysate: Insights into feast-famine dynamics and microbial community shifts

Activated sludge contains a versatile microbiome capable of converting wastes into valuable chemicals like polyhydroxyalkanoates (PHA). This study investigated the influence of repeated feast and famine phases on PHA production as well as the corresponding microbial population dynamics using waste activated sludge (WAS) as inoculum. Hydrolysate derived from rice straw was employed as a substrate for PHA production. The 16sRNA analysis results revealed that Corynebacteriaceae (40%), Bacillaceae (23%), and Pseudomonas (5%) were the primary contributors to PHA synthesis. Notably, Bacillaceae and Pseudomonas thrived in all the feast and famine phases. The achieved PHA concentration was 3.5 ± 0.2 g/L, and its structure and composition were assessed using Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR). The analysis revealed that the PHA consists of a copolymer of hydroxybutyrate (HB) and hydroxyvalerate (HV), specifically identified as Poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV).

Wood Surface Modification with Hybrid Materials Based on Multi-Walled Carbon Nanotubes

In this work, new treatments based on multi-walled carbon nanotubes (MWCNTs), MWCNTs decorated with zinc oxide (ZnO), MWCNTs decorated with hydroxyapatite (HAp) and MWCNTs decorated with silver (Ag) nanoparticles dispersed in PHBHV solution are proposed for improving sound oak wood properties. We hypothesize that the solutions containing decorated MWCNTs will be more efficient as wood consolidants, not only because of the improved mechanical properties of the treated wood but also because of the hydrophobic layer created on the wood surface. In order to test these hypotheses, the treatments’ potential was investigated by a number of complex methods, such as colorimetric parameter measurements, water absorption tests, mechanical tests, artificial aging and antifungal tests. The data confirm that the treated wood materials have moderate stability, and the color differences are not perceived with the naked eye. A significant improvement of the treated samples was observed by water absorption, humidity and mechanical tests compared to untreated wood. The best results were obtained for samples treated by brushing with solutions based on decorated CNTs, which confirms that a uniform and thicker layer is needed on the surface to ensure better protection. The wood behavior with accelerated aging revealed that the control sample degraded faster compared to the other treated samples. Antifungal tests showed that higher growth inhibition was obtained for samples treated with 0.2% MWCNTs_ZnO + PHBHV. Considering all of the obtained results, it can be concluded that the most effective treatment was MWCNTs_ZnO + PHBHV at a nanocomposite concentration of 0.2%, applied by brushing. Thus, wood protection against mold and fungi will be achieved, simultaneously ensuring improved mechanical strength and water barrier properties and therefore maintaining the structural integrity of sound oak wood over time.

Structural assessment of the bioplastic (poly-3-hydroxybutyrate) produced by Bacillus flexus Azu-A2 through cheese whey valorization

The demand for the production of biodegradable plastics has significantly increased. Bioplastics have become an essential alternative to the threats of the daily consumable plastics, sourced from fossil fuels, to the environment. Polyhydroxyalkonates (PHAs) are a ubiquitous group of bioderived and biodegradable plastics, however their production is limited by the costs associated mainly with the carbon sources. Herein, this study aims to reduce the PHAs production cost by using a by-product from the dairy industry, i.e., cheese whey (CW), as a sole carbon source. The developed process recruits an aquatic isolate, Bacillus flexus Azu-A2, and is optimized via studying various parameters using the shaking flasks technique. The results showed that the maximum PHA production (0.95 g L^-1) and PHA content (20.96%, w/w), were obtained after incubation period 72 h at 45 °C, 100 rpm agitation rate, 50% CWS concentration, pH 8.5, and 1.0 g L^-1 ammonium chloride. Physiochemically, Fourier transform infrared spectroscopy (FTIR), gas chromatography-mass spectroscopy (GC-MS), nuclear magnetic resonance (NMR), and energy-dispersive X-ray (EDX) techniques, emphasized the type of the extracted PHA as polyhydroxybutyrate (PHB). The thermal properties of PHB were measured using differential scanning calorimetry (DSC), recording melting transition temperature (Tm) at 170.96 °C. Furthermore, a scanning electron microscope (SEM) visualized a homogenous microporous structure for the thin PHB biofilm. In essence, this study highlights the ability of Bacillus flexus Azu-A2 to produce a good yield of highly purified PHB at reduced production cost from dairy CW. Consequently, the current study paves the way for an improved whey management strategy.

Microbial Community Analysis of Digested Liquids Exhibiting Different Methane Production Potential in Methane Fermentation of Swine Feces

Batch methane fermentation was conducted using seed sludge collected from six methane fermentation facilities. Swine feces were centrifuged and autoclaved, followed by its use as a substrate for methanogenesis. This "swine feces supernatant medium" facilitates the cultivation of the microbes of the seed sludge, sampling of the digested liquid using a syringe, and subculturing of the digested liquid in a subsequent medium using a syringe. Through 15 subcultures, digested liquids with high and low methane production potential were obtained, which were named "H-DS" and "L-DS," respectively. On the day 10 of cultivation, chemical oxygen demand (COD) of H-DS significantly decreased by 31% and that of L-DS did not differ significantly compared with that on the day 0 of cultivation. Acetic acid concentration of H-DS (1009 mg/L) was significantly lower than that of L-DS (2686 mg/L). These chemical characteristics indicate that organics decomposition in L-DS was not successful and suggest that H-DS has high relative abundance of bacteria decomposing organic matter and methanogen utilizing acetic acid compared with those in L-DS. Microbial community analysis revealed that Shannon index of H-DS was significantly higher than that of L-DS, and the relative abundance of acetogenic bacteria (e.g., Syntrophomonas) and acetic acid-utilizing methanogen (Methanosarcina) in H-DS was significantly higher than that in L-DS. Thus, the high methane production potential of H-DS might be attributable to the smooth flow from acetogenesis to methanogenesis step in the methane fermentation, compared with the case of L-DS.

Polyhydroxyalkanoate (PHA): applications in drug delivery and tissue engineering

INTRODUCTION

The applications of naturally obtained polymers are tremendously increased due to them being biocompatible, biodegradable, environmentally friendly and renewable in nature. Among them, polyhydroxyalkanoates are widely studied and they can be utilized in many areas of human life research such as drug delivery, tissue engineering, and other medical applications.

AREAS COVERED

This review provides an overview of the polyhydroxyalkanoates biosynthesis and their possible applications in drug delivery in the range of micro- and nano-size. Moreover, the possible applications in tissue engineering are covered considering macro- and microporous scaffolds and extracellular matrix analogs.

EXPERT COMMENTARY

The majority of synthetic plastics are non-biodegradable so, in the last years, a renewed interest is growing to develop alternative processes to produce biologically derived polymers. Among them, PHAs present good properties such as high immunotolerance, low toxicity, biodegradability, so, they are promisingly using as biomaterials in biomedical applications.

Biolytic extraction of poly(3-hydroxybutyrate) from Bacillus megaterium Ti3 using the lytic enzyme of Streptomyces albus Tia1

The applicability of Streptomyces sp. cell lytic enzymes for devising a simple and competent biological polyhydroxyalkanoate (PHA) recovery approach from Bacillus megaterium cells was investigated. B. megaterium strain Ti3 produced 50% (w/w) PHA using glucose as carbon source. The intracellular PHA was recovered employing a non-PHA accumulating actinomycetes (Tia1) identified as Streptomyces albus, having potent lytic activity against living and heat inactivated B. megaterium. Interestingly, maximum biomass (2.53 ± 0.6 g/L by 24 h) of the lytic actinomycete was obtained in PHA production medium itself thus circumventing the prior actinomycete acclimatization just by co-inoculation with B. megaterium as an inducer. Maximum lytic activity was observed at pH 6.0, 40 °C, 220 mg of biomass and 33.3 mL of concentrated culture filtrate in a 100 mL reaction mixture. Preliminary biochemical investigations confirmed the proteolytic and caseinolytic nature of the lytic enzyme. PHA yield of 0.55 g/g by co-inoculation extraction approach was comparable with the conventional sodium hypochlorite based extraction method. Interestingly, S. albus also demonstrated a broad spectrum lytic potential against varied Gram-negative and Gram-positive PHA producers highlighting the extensive applicability of this biolytic PHA recovery approach. The lytic enzyme retained almost 100% relative activity on storage at -20 °C upto two months. 1H Nuclear magnetic resonance analysis of the extracted polymer confirmed it as a homopolymer composed of 3-hydroxybutyrate monomeric units. This is the first report on Streptomyces sp. based biological and eco-friendly, intracellular PHA recovery from Bacillus spp.

Synthesis of Poly-(R-hydroxyalkanoates) byCupriavidus necatorATCC 17699 Using Mexican Avocado(Persea americana)Oil as a Carbon Source

Poly-R-hydroxyalkanoates (PHAs) are polymers produced by a vast number of bacterial species under stress conditions. PHAs exhibit different thermal and mechanical properties that depend on their molecular structure. In this work, PHAs were produced using avocado oil as the carbon source.Cupriavidus necatorH16 was cultured in three-stage fermentation using fructose during the cell growth stages and avocado oil during the PHA synthesis stage. Different concentrations of avocado oil were used during the third stage to test the incorporation of various monomeric units into the PHAs. Biomass and PHA production were measured during the fermentation. DSC, FTIR, and gas chromatography analysis aided the PHA characterization. Different proportions of 3-hydroxyvalerate were present in the 3-hydroxybutyrate main chain depending on the concentration of avocado oil. The results suggest that avocado oil is a viable new substrate for PHA production.