Coproduction of 5-Aminovalerate and δ-Valerolactam for the Synthesis of Nylon 5 From L-Lysine in Escherichia coli

The compounds 5-aminovalerate and δ-valerolactam are important building blocks that can be used to synthesize bioplastics. The production of 5-aminovalerate and δ-valerolactam in microorganisms provides an ideal source that reduces the cost. To achieve efficient biobased coproduction of 5-aminovalerate and δ-valerolactam in Escherichia coli, a single biotransformation step from L-lysine was constructed. First, an equilibrium mixture was formed by L-lysine α-oxidase RaiP from Scomber japonicus. In addition, by adjusting the pH and H2O2 concentration, the titers of 5-aminovalerate and δ-valerolactam reached 10.24 and 1.82 g/L from 40 g/L L-lysine HCl at pH 5.0 and 10 mM H2O2, respectively. With the optimized pH value, the δ-valerolactam titer was improved to 6.88 g/L at pH 9.0 with a molar yield of 0.35 mol/mol lysine. The ratio of 5AVA and δ-valerolactam was obviously affected by pH value. The ratio of 5AVA and δ-valerolactam could be obtained in the range of 5.63:1–0.58:1 at pH 5.0–9.0 from the equilibrium mixture. As a result, the simultaneous synthesis of 5-aminovalerate and δ-valerolactam from L-lysine in Escherichia coli is highly promising. To our knowledge, this result constitutes the highest δ-valerolactam titer reported by biological methods. In summary, a commercially implied bioprocess developed for the coproduction of 5-aminovalerate and δ-valerolactam using engineered Escherichia coli.

In-Liquid Plasma: A Novel Tool for Nanofabrication

This chapter focuses on synthesising nanomaterials using an emerging technology called In-Liquid Plasma, i.e., plasma generation inside a liquid. The generation of various reactive species and energetic electrons in the plasma zone plays a crucial role in synthesising nanomaterials. They act as the reducing agent. Non-requirement of the toxic chemical reducing agents make In-Liquid Plasma an environmentally friendly green approach to fabricate nanomaterials. This method enables the simultaneous synthesis of nanoparticles from the electrode material and liquid precursor, which gains much importance on the single-step synthesis of nanocomposites. Moreover, it gives flexibility in controlling both the physical and chemical parameters, which provide fine-tuning required for the size, shape and composition of nanomaterials.

Simultaneous Synthesis and Consolidation of Nanostructured HfB2–SiC Composite

A dense nanostructured 2HfB2-SiC composite was simultaneously synthesized and consolidated by the pulsed current activated sintering method in one step within very short time (two minutes) from mechanically activated 2Hf, B4C and Si powders. Simultaneous combustion synthesis and consolidation were achieved through the combination of the effects of the pulsed current and mechanical pressure. A highly dense 2HfB2–SiC composite with 97.5% relative density was achieved under the simultaneous application of a pressure of 80 MPa and the pulsed current. The fracture toughness of the 2HfB2–SiC composite was higher than that of monolithic HfB2.

Biotechnological Potential of the Acinetobacter Genus Bacteria

Until recently, there were rare scientific reports on the biotechnological potential of non-pathogenic bacteria of the Acinetobacter genus. Although the first reports about the practically valuable properties of these bacteria date back to the 70s and 80s of the twentieth century and concerned the synthesis of the emulsan bioemulsifier. In the last decade, interest in representatives of the Acinetobacter genus as objects of biotechnology has significantly increased. The review presents current literature data on the synthesis by bacteria of this genus of high-molecular emulsifiers, low-molecular biosurfactants of glyco- and aminolipid nature, enzymes (lipase, agarase, chondroitinase), phytohormones, as well as their ability to solubilize phosphates and decompose various xenobiotics (aliphatic and aromatic hydrocarbons, pesticides, insecticides). Prospects for practical application of Acinetobacter bacteria and the metabolites synthesized by them in environmental technologies, agriculture, various industries and medicine are discussed. The data of own experimental studies on the synthesis and biological activity (antimicrobial, anti-adhesive, ability to destroy biofilms) of biosurfactants synthesized by A. calcoaceticus IMV B-7241 strain and their role in the degradation of oil pollutants, including complex ones with heavy metals, are presented. The ability of A. calcoaceticus IMV B-7241 to the simultaneous synthesis of phytohormones (auxins, cytokinins, gibberellins) and biosurfactants with antimicrobial activity against phytopathogenic bacteria allows us to consider this strain as promising for practical use in crop production to increase crop yields.