Multi-Step Enzymatic Synthesis of 1,9-Nonanedioic Acid from a Renewable Fatty Acid and Its Application for the Enzymatic Production of Biopolyesters

Structure modeling-based characterization of ChnD, the 6-hydroxyhexanoate dehydrogenase from Acinetobacter sp. strain NCIMB 9871

α,ω-Dicarboxylic acids, ω-aminoalkanoic acids, and α,ω-diaminoalkanes are valuable building blocks for the production of biopolyesters and biopolyamides. One of the key steps in producing these chemicals is the oxidation of ω-hydroxycarboxylic acids using alcohol dehydrogenases (e.g., ChnD of Acinetobacter sp. NCIMB 9871). However, the reaction and structural features of these enzymes remain mostly undiscovered. Thereby, we have investigated characteristics of ChnD based on enzyme kinetics, substrate-docking simulations, and mutation studies. Kinetic analysis revealed a distinct preference of ChnD for medium chain ω-hydroxycarboxylic acids, with the highest catalytic efficiency of 18.0 mM-1s-1 for 12-hydroxydodecanoic acid among C6 to C12 ω-hydroxycarboxylic acids. The high catalytic efficiency was attributed to the positive interactions between the carboxyl group of the substrates and the guanidino group of two arginine residues (i.e., Arg62 and Arg266) in the substrate binding site. The ChnD_R62L variant showed the increased efficiency and affinity, particularly for fatty alcohols (i.e., C6-C10) and branched-chain fatty alcohols, such as 3-methyl-2-buten-1-ol. Overall, this study contributes to the deeper understanding of medium-chain primary aliphatic alcohol dehydrogenases and their applications for the production of industrially relevant chemicals such as α,ω-dicarboxylic acids, ω-aminoalkanoic acids, and α,ω-diaminoalkanes from renewable biomass.

Chitosan-based buccal mucoadhesive patches to enhance the systemic bioavailability of tizanidine

Tizanidine hydrochloride (TZN) is a muscle relaxant used to treat a variety of disorders such as painful muscle spasms and chronic spasticity. TZN has low oral bioavailability due to extensive first-pass metabolism and is used orally at a dose of 6-24 mg per day. In the present study, buccal patches were prepared by solvent casting method using chitosan glutamate (Chi-Glu) and novel chitosan azelate (Chi-Aze) which was synthesised in-house for the first time, to enhance the bioavailability of TZN by bypassing first-pass metabolism. The characterisation, mucoadhesion and drug release studies were performed. Chi-Aze patches retained their integrity longer in the buccal medium and showed higher ex vivo drug permeability compared to that prepared with Chi-Glu. In vivo studies revealed that buccal formulation fabricated with Chi-Aze (3%) showed approx 3 times more bioavailability than the orally administered commercial product. Results of the studies indicate that Chi-Aze, prepared by conjugation of chitosan and a fatty acid, the patch formulation is a promising buccal mucoadhesive system due to the physical stability in buccal medium, the good mucoadhesiveness and the high TZN bioavailability. Moreover, Chi-Aze patch might be an alternative to oral formulations of TZN to reduce the dose and frequency of drug administration.

Recent Advances in the Enzymatic Synthesis of Polyester

Polyester is a kind of polymer composed of ester bond-linked polybasic acids and polyol. This type of polymer has a wide range of applications in various industries, such as automotive, furniture, coatings, packaging, and biomedical. The traditional process of synthesizing polyester mainly uses metal catalyst polymerization under high-temperature. This condition may have problems with metal residue and undesired side reactions. As an alternative, enzyme-catalyzed polymerization is evolving rapidly due to the metal-free residue, satisfactory biocompatibility, and mild reaction conditions. This article presented the reaction modes of enzyme-catalyzed ring-opening polymerization and enzyme-catalyzed polycondensation and their combinations, respectively. In addition, the article also summarized how lipase-catalyzed the polymerization of polyester, which includes (i) the distinctive features of lipase, (ii) the lipase-catalyzed polymerization and its mechanism, and (iii) the lipase stability under organic solvent and high-temperature conditions. In addition, this article also focused on the advantages and disadvantages of enzyme-catalyzed polyester synthesis under different solvent systems, including organic solvent systems, solvent-free systems, and green solvent systems. The challenges of enzyme optimization and process equipment innovation for further industrialization of enzyme-catalyzed polyester synthesis were also discussed in this article.

Valorization of Soy Lecithin by Enzyme Cascade Reactions Including a Phospholipase A2, a Fatty Acid Double-Bond Hydratase, and/or a Photoactivated Decarboxylase

A huge amount of phospholipids or lecithin is produced as a byproduct in the vegetable oil industry. However, most are just used as a feed additive. This study has focused on enzymatic valorization of lecithin. This was exploited by enzymatic transformation of soy lecithin into lysolecithin liposomes, including functional free fatty acids, hydroxy fatty acids, hydrocarbons, or secondary fatty alcohols. One of the representative examples was the preparation of lysolecithin liposomes containing secondary fatty alcohols [e.g., 9-Hydroxyheptadec-11-ene (9) and 9-heptadecanol (10)] by using a phospholipase A2 from Streptomyces violaceoruber, a fatty acid double-bond hydratase from Stenotrophomonas maltophilia, and a photoactivated decarboxylase from Chlorella variabilis NC64A. The engineered liposomes turned out to range ca. 144 nm in diameter by dynamic light scattering analysis. Thereby, this study will contribute to application of functional fatty acids and their derivatives as well as valorization of lecithin for the food and cosmetic industries.