The Synthesis, Characterization and Applications of Polyhydroxyalkanoates (PHAs) and PHA-Based Nanoparticles

Polyhydroxyalkanoates (PHAs) are storage granules found in bacteria that are essentially hydroxy fatty acid polyesters. PHA molecules appear in variety of structures, and amongst all types of PHAs, polyhydroxybutyrate (PHB) is used in versatile fields as it is a biodegradable, biocompatible, and ecologically safe thermoplastic. The unique physicochemical characteristics of these PHAs have made them applicable in nanotechnology, tissue engineering, and other biomedical applications. In this review, the optimization, extraction, and characterization of PHAs are described. Their production and application in nanotechnology are also portrayed in this review, and the precise and various production methods of PHA-based nanoparticles, such as emulsion solvent diffusion, nanoprecipitation, and dialysis are discussed. The characterization techniques such as UV-Vis, FTIR, SEM, Zeta Potential, and XRD are also elaborated.

Anti-Mycoplasma Activity of Bacilotetrins C–E, Cyclic Lipodepsipeptides from the Marine-Derived Bacillus subtilis and Structure Revision of Bacilotetrins A and B

Mycoplasma hyorhinis most commonly causes polyserositis and arthritis in swine and is a common contaminant during the cell culture in the laboratory. In our continuing research for diverse bioactive compounds from Bacillus subtilis 109GGC020, we discovered uncommon cyclic lipotetrapeptides showing inhibitory activities against M. hyorhinis with similar structures to previously reported bacilotetrins A and B. Bacilotetrins C–E (1–3), new cyclic lipodepsipeptides, were isolated from the EtOAc extract obtained from the fermentation of marine-derived Bacillus subtilis isolated from a marine sponge sample collected from the Gageo reef, Republic of Korea. The structures of 1–3, consisting of three leucine residues, one glutamic acid, and a β-hydroxy fatty acid, were elucidated by detailed analysis of 1D, 2D NMR, and HR-ESIMS data. The absolute configurations of the amino acids and β-hydroxy fatty acid were established by advanced Marfey’s method and Mosher’s method, respectively. The localization of L- and D-amino acids within the compounds was determined by retention time comparison of each purchased dipeptide standard to the partial hydrolysate products using LC-MS. Compounds 1–3 exhibited anti-mycoplasma activity, with an MIC value of 31 μg/mL, twofold stronger than that of the positive control, BioMycoX®. Detailed analysis and comparison of the spectroscopic data between bacilotetrins A (4) and B (5) and 1–3 led us to revise the structures of 4 and 5.

Two Novel Lyso-Ornithine Lipids Isolated from an Arctic Marine Lacinutrix sp. Bacterium

The Lacinutrix genus was discovered in 2005 and includes 12 Gram-negative bacterial species. To the best of our knowledge, the secondary metabolite production potential of this genus has not been explored before, and examination of Lacinutrix species may reveal novel chemistry. As part of a screening project of Arctic marine bacteria, the Lacinutrix sp. strain M09B143 was cultivated, extracted, fractionated and tested for antibacterial and cytotoxic activities. One fraction had antibacterial activity and was subjected to mass spectrometry analysis, which revealed two compounds with elemental composition that did not match any known compounds in databases. This resulted in the identification and isolation of two novel isobranched lyso-ornithine lipids, whose structures were elucidated by mass spectrometry and NMR spectroscopy. Lyso-ornithine lipids consist of a 3-hydroxy fatty acid linked to the alpha amino group of an ornithine amino acid through an amide bond. The fatty acid chains were determined to be iso-C15:0 (1) and iso-C16:0 (2). Compound 1 was active against the Gram-positive S. agalactiae, while 2 showed cytotoxic activity against A2058 human melanoma cells.

Molecular Dynamics Study of Surfactin Interaction with Lipid Bilayer Membranes

Background: Surfactin is a cyclic heptapeptide that is closed by a β-hydroxy fatty acid chain. This potent biosurfactant is produced by different Bacillus subtilis strains. This lipopeptide has numerous attractive biological activities, including antibacterial, antiviral, antimycoplasma, hemolytic, and other different and powerful surface and interface activities. Methods: Understanding how surfactin binds to different membranes and its mechanism of action can help us modify and optimize its structure to improve the potential efficacy of this lipopeptide in the future. For this purpose, we studied the interaction of this lipopeptide with two types of lipid bilayer models, including palmitoyl-oleoyl-glycero- phosphocholine (POPC) and palmitoyl-oleoyl-phosphtidylglycerol (POPG) as the prokaryotic and eukaryotic membrane models, respectively. Results: The obtained data have shown that the tendency of surfactin for these membranes is different. According to the analysis, this molecule binds to both membranes peripherally, and its interaction with the negative membrane is also more potent compared to the zwitterionic membrane. Moreover, we found that surfactin destabilized POPG more than POPC. This suggests that surfactin may act by modifying the membrane’s bulk physical properties. Conclusions: As a final point, this study has shown that surfactin has different behaviors in the eukaryotic and prokaryotic cell membranes and can modify and amplify its action in order to use it for antibacterial drugs.

Overexpression of the Plant Medium-chain Acyl-carrier Protein Thioesterase BTE for the Overproduction of the nC14-surfactin Isoform with Promising MEOR Applications

BackgroundSurfactin, a representative biosurfactant of popeptide mainly produced by Bacillus subtilis, consists of a cyclic heptapeptide linked to a β-hydroxy fatty acid chain. The functional activity of surfactin is closely related to the length and isomerism of the fatty acid chain. ResultsIn this study, the plant medium-chain acyl-carrier protein (ACP) thioesterase (BTE) from Umbellularia californica was overexpressed in a recombinant surfactin production strain based on B. subtilis 168. As a result, the surfactin yield after 24 h of cultivation improved by 23%, and the production rate increased from 0.112 to 0.177 g/L/h. The isoforms identified by RP-HPLC and GC-MS showed that the proportion of nC14-surfactin increased 6.4 times compared to the control strain. A comparison of further properties revealed that the product with more nC14-surfactin had higher surface activity and better performance in oil-washing. Finally, the product with more nC14-surfactin isoform had a higher hydrocarbon-emulsification index, and it increased the water-wettability of the oil-saturated silicate surface. ConclusionThe obtained results provide an original approach to modify the fatty acid chain of surfactin and further demonstrate the importance of the length and isomerism of the β-hydroxy fatty acid chain for the MEOR application of surfactin.