Sophorolipid-Derived Unsaturated and Epoxy Fatty Acid Estolides as Plasticizers for Poly(3-Hydroxybutyrate)

Natural antimicrobial systems protected by complex polyhydroxyalkanoate matrices for food biopackaging applications - A review

Interest is growing in entrapping natural antimicrobial compounds (NACs) within polyhydroxyalkanoates (PHAs) to produce active food-biopackaging systems. PHAs are versatile polymeric macromolecules that can protect NAC activity by entrapment. This work reviews 75 original papers and 18 patents published in the last 11 years concerning PHAs as matrices for NACs to summarize the physicochemical properties, release, and antimicrobial activities of systems fabricated from PHAs and NACs (PHA/NAC systems). PHA/NAC systems have recently been used as active food biopackaging systems to inactivate foodborne pathogens and prolong food shelf life. PHAs protect NACs by increasing the degradation temperature of some NACs and decreasing their loss of mass when heated. Some NACs also transform the PHA/NAC systems into more thermostable, flexible, and resistant when interacting with PHAs while also improving the barrier properties of the systems. NAC release and activity are also prolonged when NACs are trapped within PHAs. PHA/NAC systems, therefore, represent ecologically friendly materials with promising applications.

Bioconversion of Food Waste to produce Industrial-scale Sophorolipid Syrup and Crystals: dynamic Life Cycle Assessment (dLCA) of Emerging Biotechnologies

Bioconversion of food waste into sophorolipid-based biosurfactants is a promising emerging technology. It is important to evaluate the environmental impacts associated with the latest advancements in sophorolipid production as it matures to maximize sustainability on scale-up. This study takes a dynamic Life Cycle Assessment (dLCA) approach to address the inherent uncertainties and evaluate the environmental performances. It demonstrates the dLCA framework by conducting the new traversal of food waste-derived industrial-scale sophorolipid production, with the combination of Techno-Economic Analysis (TEA). A systematic investigation of the environmental-economic implications of the two pathways to produce SL crystals and syrup. The global warming potential (GWP) for 1 kg of SL crystals and syrup was 7.9 kg CO₂ eq. and 5.7 kg CO₂ eq., respectively. The Ashby-like charts based on the LCA and TEA results at the pilot plant highlighted the trade-offs between systemic environmental costs and economic benefits for design decisions.

Plasticization of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with an Oligomeric Polyester: Miscibility and Effect of the Microstructure and Plasticizer Distribution on Thermal and Mechanical Properties

In the last few decades, many efforts have been made to make poly(3-hydroxybutyrate) (PHB) and its copolymers more suitable for industrial production and large-scale use. Plasticization, especially using biodegradable oligomeric plasticizers, has been one of the strategies for this purpose. However, PHB and its copolymers generally present low miscibility with plasticizers. An understanding of the plasticizer distribution between the mobile and rigid amorphous phases and how this influences thermal, mechanical, and morphological properties remains a challenge. Herein, formulations of poly(hydroxybutyrate-co-valerate) (PHBV) plasticized with an oligomeric polyester based on lactic acid, adipic acid, and 1,2-propanediol (PLAP) were prepared by melt extrusion. The effects of the PLAP content on the processability, miscibility, and microstructure of the semicrystalline PHBV and on the thermal, morphological, and mechanical properties of the formulations were investigated. The compositions of the mobile and rigid amorphous phases of the PHBV/PLAP formulations were easily estimated by combining dynamic mechanical data and the Fox equation, which showed a heterogeneous distribution of PLAP in these two phases. An increase in the PLAP mass fraction in the formulations led to progressive changes in the composition of the amorphous phases, an increase of both crystalline lamellae and interlamellar layer thickness, and a decrease in the melting and glass transition temperatures as well as the PHBV stiffness. The Flory-Huggins interaction parameter varied with the formulation composition in the range of -0.299 to -0.081. The critical PLAP mass fraction of 0.37 obtained from thermodynamic data is close to the value estimated from dynamic mechanical analysis (DMA) data and the Fox equation. The mechanical properties showed a close relationship with the distribution of PLAP in the rigid and mobile amorphous phases as well as with the microstructure of the crystalline phase of PHBV in the formulations.

Fatty Acid Hydratases: Versatile Catalysts to Access Hydroxy Fatty Acids in Efficient Syntheses of Industrial Interest

The utilization of hydroxy fatty acids has gained more and more attention due to its applicability in many industrial building blocks that require it, for example, polymers or fragrances. Furthermore, hydroxy fatty acids are accessible from biorenewables, thus contributing to a more sustainable raw material basis for industrial chemicals. Therefore, a range of investigations were done on fatty acid hydratases (FAHs), since these enzymes catalyze the addition of water to an unsaturated fatty acid, thus providing an elegant route towards hydroxy-substituted fatty acids. Besides the discovery and characterization of fatty acid hydratases (FAHs), the design and optimization of syntheses with these enzymes, the implementation in elaborate cascades, and the improvement of these biocatalysts, by way of mutation in terms of the substrate scope, has been investigated. This mini-review focuses on the research done on process development using fatty acid hydratases as a catalyst. It is notable that biotransformations, running at impressive substrate loadings of up to 280 g L−1, have been realized. A further topic of this mini-review is the implementation of fatty acid hydratases in cascade reactions. In such cascades, fatty acid hydratases were, in particular, combined with alcohol dehydrogenases (ADH), Baeyer-Villiger monooxygenases (BVMO), transaminases (TA) and hydrolases, thus enabling access to a broad variety of molecules that are of industrial interest.

Application of Glycolipid Biosurfactants as Surface Modifiers in Bioplastics

Surface properties of cast films of poly(lactic acid) (PLA) containing 1 wt% of several glycolipid-type biosurfactants (BSs) were investigated. The wettability of PLA films containing a homologue of mannosylerythritol lipids (MEL-B), lactone-form sophorolipid (LSL), or cellobiose lipid (CL) was drastically higher than that of untreated PLA and several synthetic surfactants-containing PLA. Surface wettability was also dependent on the hydrophilicity of the substrate used during solvent casting of the PLA films. The wetting behavior of the opposing sides of MEL-B-containing films prepared on glass substrates differed significantly; the contact angle on the side of the film that had been in contact with the glass surface was significantly lower than that obtained on the side of the film that had been in contact with air. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis results showed that the MEL in MEL-B-containing thin PLA cast films was localized to a thin surface layer. These results suggest self-assembly of MEL-B and micro-phase separation between the PLA matrix and MEL-B domains. This resulted in the localization and orientation of MEL-B at the surface of the cast PLA film, which determined its specific wetting behavior.

In-Situ Synthesis and Characterization of Biodegradable Estolides via Epoxidation from Canola Biodiesel

Research on the formulation of estolides from plant seed oils has attracted substantial attention due to their favorable low-temperature properties and environmentally friendly nature. The present research investigates the formulation of canola biodiesel derived estolides for low-temperature applications. The dual-step research method includes ring opening of epoxidized canola biodiesel in the presence of oleic acid, followed by esterification with oleic acid to produce estolides using a mesoporous aluminosilicates possessing Modernite Framework Inverted (MFI) type pentasil structure as a heterogeneous acidic catalyst. Prepared catalyst was characterized to measure the properties essential for the effective catalysis. The catalyst demonstrated promising activity for the estolides formation, >95% conversion was achieved at 110 °C for 6 h using 15 wt % of catalyst loading. 1H NMR technique and oxirane oxygen titrimetric analysis were employed to determine product purity. Physicochemical properties of the reaction products were determined by standard methods and characterization results revealed that the formulated estolides had improved low-temperature, lubricity and rheological properties, and thermo-oxidative stability. Also, biodegradability of the estolides was found to be 92% within 28 days as per the bio-kinetic model. Wear scar diameter of 106 µm was noticed for 10% of alkoxide blend with standard diesel fuel. Overall, outcomes of the physicochemical characterization data indicated that the prepared estolides can act as possible alternative bio-lubricant basestock for various low-temperature applications.

Burkholderia sacchari DSM 17165: A source of compositionally-tunable block-copolymeric short-chain poly(hydroxyalkanoates) from xylose and levulinic acid

Burkholderia sacchari was used to produce poly-3-hydroxybutyrate-co-3-hydroxyvalerate block copolymers from xylose and levulinic acid. Levulinic acid was the preferred substrate resulting in 3-hydroxyvalerate (3HV) contents as high as 95 mol% at 24 h. The 3HB:3HV ratios were controlled by the initial levulinic acid media concentration and fermentation length. Higher levulinic acid concentrations and longer durations, resulted in polymers with two glass transition temperatures, each approximating those associated with poly-3HB and poly-3HV. ¹³C NMR confirmed the presence of high concentrations of 3HB-3HB and 3HV-3HV homopolymeric dyads, while mass spectrometry of the partial hydrolysis products did not conform to Bernoullian statistics for randomness, confirming block sequences. MS/MS analysis of specific oligomers showed the mass-loss of 86 amu (a 3HB unit) and 100 amu (a 3HV unit) attesting to some randomness within the polymers. This study verifies the potential for producing Poly-3HB-block-3HV copolymers from inexpensive biorenewable feedstocks without sequential addition of carbon sources.