Application of Polyhydroxyalkanoate Granules for Sizing of Paper

Physicochemical Characterisation of Polysaccharide Films with Embedded Bioactive Substances

In this study, sodium carboxymethyl cellulose (CMCNa) bioactive films, crosslinked with citric acid (CA), were prepared and comprehensively examined for their suitability in various applications, focusing on food packaging. The films displayed favourable properties, including appropriate thickness, transparency, and moisture content, essential for packaging purposes. Moreover, the films exhibited excellent moisture absorption rate and barrier properties, attributed to the high concentration of CMCNa and the inclusion of a CA. These films presented no significant effect of crosslinking and bioactive components on their mechanical strength, as evidenced by tensile strength and elongation at break values. Thermal stability was demonstrated in the distinct weight loss events at different temperature ranges, with crosslinking contributing to slightly enhanced thermal performance. Furthermore, the films showed varying antioxidant activity levels, influenced by temperature and the solubility of the films in different media, indicating their potential for diverse applications. Overall, these bioactive films showed promise as versatile materials with desirable properties for food packaging and related applications, where the controlled release of bioactive components is advantageous for enhancing the shelf life and safety of food products. These findings contribute to the growing research in biodegradable and functional food packaging materials.

Production of polyhydroxyalkanoates from renewable resources: a review on prospects, challenges and applications

Bioplastics replace synthetic plastics of petrochemical origin, which contributes challenge to both polymer quality and economics. Novel polyhydroxyalkanoates (PHA)-composite materials, with desirable product quality, could be developed, thus targeting the global plastics market, in the coming years. It is possible that PHA can be a greener substitute for their petroleum-based competitors since they are simply decomposed, which may lessen the pressure on municipal and industrial waste management systems. PHA production has proven to be the bottleneck in industrial application and commercialization because of the high price of carbon substrates and downstream processes required to achieve reliability. Bacterial PHA production by these municipal and industrial wastes, which act as a cheap, renewable carbon substrate, eliminates waste management hassles and acts as an efficient substitute for synthetic plastics. In the present review, challenges and opportunities related to the commercialization of polyhydroxyalkanoates are discussed and presented. Moreover, it discusses critical steps of their production process, feedstock evaluation, optimization strategies, and downstream processes. This information may provide us the complete utilization of bacterial PHA during possible applications in packaging, nutrition, medicine, and pharmaceuticals.

Intelligent high-tech coating of natural biopolymer layers

Polymeric materials play a vital role in our daily life, but the growing concern for the environment demands economical and natural biopolymers that can be cross-linked to create technologically innovative lightweight materials. Their cellular matrix with extreme flexibility makes them highly acceptable for application prospects in material science, engineering, and biomedical applications. Furthermore, their biocompatibility, mechanical properties, and structural diversity provide a gateway to research them to form technologically important materials. In the light of the same, the review covers cellulose derivatives. The first section of the study covers the general properties and applications of cellulose and its derivatives. Then, the biopolymers are characterised based on their dielectric properties, crystallinity, rheology, and mechanical properties. An in-depth analysis of the diffuse process of swelling and dissolution followed by a brief discussion on diffusion and diffusion of crosslinking has been done. The review also covers a section on swelling and swelling kinetics of carboxymethyl cellulose (CMC) and hydroxyethyl cellulose (HEC). The examination of all the aforementioned parameters gives an insight into the future aspects of the biopolymers. Lastly, the study briefly covers some preferred choices of cross-linking agents and their effect on the biopolymers.

Production of the Polyhydroxyalkanoate PHBV from Ricotta Cheese Exhausted Whey by Haloferax mediterranei Fermentation

In the last decade, the dairy industry underwent a rapid expansion due to the increasing demand of milk-based products, resulting in high quantity of wastewater, i.e., whey and ricotta cheese exhausted whey (RCEW). Although containing high content of nutritional compounds, dairy by-products are still disposed as waste rather being reintroduced in a new production chain, hence leading to environmental and economic issues. This study proposes a new biotechnological approach based on the combination of membrane filtration and fermentation to produce poly-hydroxyalkanoates (PHA), biodegradable bioplastics candidate as an alternative to petroleum-derived plastics. The protocol, exploiting the metabolic capability Haloferax mediterranei to synthesize PHA from RCEW carbon sources, was set up under laboratory and pilot scale conditions. A multi-step fractionation was used to recover a RCEW fraction containing 12.6% (w/v) of lactose, then subjected to an enzymatic treatment aimed at releasing glucose and galactose. Fermentation conditions (culture medium for the microorganism propagation, inoculum size, time, and temperature of incubation) were selected according to the maximization of polymer synthesis, under in-flasks experiments. The PHA production was then tested using a bioreactor system, under stable and monitored pH, temperature, and stirring conditions. The amount of the polymer recovered corresponded to 1.18 g/L. The differential scanning calorimetry (DSC) analysis revealed the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) as the polymer synthesized, with a relatively high presence of hydroxyvalerate (HV). Identity and purity of the polymer were confirmed by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and X-ray photoelectron (XPS) spectroscopy analyses. By combining the fractionation of RCEW, one of the most abundant by-products from the agri-food industry, and the use of the halophile Hfx mediterranei, the production of PHBV with high purity and low crystallinity has successfully been optimized. The process, tested up to pilot scale conditions, may be further implemented (e.g., through fed-batch systems) and used for large-scale production of bioplastics, reducing the economical and environmental issues related the RCEW disposal.

Enzymatic Hydrolysis of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) Scaffolds

Polyhydroxyalkanoates (PHAs) are hydrolyzable bio-polyesters. The possibility of utilizing lignocellulosic waste by-products and grape pomace as carbon sources for PHA biosynthesis was investigated. PHAs were biosynthesized by employing Cupriavidus necator grown on fructose (PHBV-1) or grape sugar extract (PHBV-2). Fifty grams of lyophilized grape sugar extract contained 19.2 g of glucose, 19.1 g of fructose, 2.7 g of pectin, 0.52 g of polyphenols, 0.51 g of flavonoids and 7.97 g of non-identified rest compounds. The grape sugar extract supported the higher production of biomass and modified the composition of PHBV-2. The biosynthesized PHAs served as matrices for the preparation of the scaffolds. The PHBV-2 scaffolds had about 44.2% lower crystallinity compared to the PHBV-1 scaffolds. The degree of crystallinity markedly influenced the mechanical behavior and enzymatic hydrolysis of the PHA scaffolds in the synthetic gastric juice and phosphate buffer saline solution with the lipase for 81 days. The higher proportion of amorphous moieties in PHBV-2 accelerated enzymatic hydrolysis. After 81-days of lasting enzymatic hydrolysis, the morphological changes of the PHBV-1 scaffolds were negligible compared to the visible destruction of the PHBV-2 scaffolds. These results indicated that the presence of pectin and phenolic moieties in PHBV may markedly change the semi-crystalline character of PHBV, as well as its mechanical properties and the course of abiotic or enzymatic hydrolysis.

Chloroform induces outstanding crystallization of poly(hydroxybutyrate) (PHB) vesicles within bacteria

Poly[(R)-3-hydroxyalkanoate]s or PHAs are aliphatic polyesters produced by numerous microorganisms. They are accumulated as energy and carbon reserve in the form of small intracellular vesicles. Poly[(R)-3-hydroxybutyrate] (PHB) is the most ubiquitous and simplest PHA. An atomic force microscope coupled with a tunable infrared laser (AFM-IR) was used to record highly spatially resolved infrared spectra of commercial purified PHB and native PHB within bacteria. For the first time, the crystallinity degree of native PHB within vesicle has been directly evaluated in situ without alteration due to the measure or extraction and purification steps of the polymer: native PHB is in crystalline state at 15% whereas crystallinity degree reaches 57% in commercial PHB. Chloroform addition on native PHB induces crystallization of the polymer within bacteria up to 60%. This possibility of probing and changing the physical state of polymer in situ could open alternative ways of production for PHB and others biopolymers. Graphical abstract An atomic force microscope coupled with a tunable infrared laser (AFM-IR) has been used to record local infrared spectra of biopolymer PHB within bacteria. Deconvolution of those spectra has allowed to determine in situ the crystallinity degree of native PHB.

Enzyme and metabolic engineering for the production of novel biopolymers: crossover of biological and chemical processes

The development of synthetic biology has transformed microbes into useful factories for producing valuable polymers and/or their precursors from renewable biomass. Recent progress at the interface of chemistry and biology has enabled the production of a variety of new biopolymers with properties that substantially differ from their petroleum-derived counterparts. This review touches on recent trials and achievements in the field of biopolymer synthesis, including chemo-enzymatically synthesized aliphatic polyesters, wholly biosynthesized lactate-based polyesters, polyhydroxyalkanoates and other unusual bacterially synthesized polyesters. The expanding diversities in structure and the material properties of biopolymers are key for exploring practical applications. The enzyme and metabolic engineering approaches toward this goal are discussed by shedding light on the successful case studies.