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Abstract Background Dodecanedioic acid (DDA), a typical medium-chain dicarboxylic fatty acid with widespread applications, has a great synthetic value and a huge industrial market demand. Currently, a sustainable, eco-friendly and efficient process is desired for dodecanedioic acid production. Results Herein, a multi-enzymatic cascade was designed and constructed for the production of DDA from linoleic acid based on the lipoxygenase pathway in plants. The cascade is composed of lipoxygenase, hydroperoxide lyase, aldehyde dehydrogenase, and unidentified double-bond reductase in E. coli for the main cascade reactions, as well as NADH oxidase for cofactor recycling. The four component enzymes involved in the cascade were co-expressed in E. coli, together with the endogenous double-bond reductase of E. coli. After optimizing the reaction conditions of the rate-limiting step, 43.8 g L− 1 d− 1 of DDA was obtained by a whole-cell one-pot process starting from renewable linoleic acid. Conclusions Through engineering of the reaction system and co-expressing the component enzymes, a sustainable and eco-friendly DDA biosynthesis route was set up in E. coli, which afforded the highest space time yield for DDA production among the current artificial multi-enzymatic routes derived from the LOX-pathway, and the productivity achieved here ranks the second highest among the current research progress in DDA biosynthesis. Graphical Abstract

Sugar esters in tobacco play an important role as precursors generating tobacco aroma species, and their presence significantly influence the quality of tobacco leaves. Typically present in trace amounts, sugar esters in tobacco exhibit a diverse range of isomers, making their separation and analysis a significant challenge. To address this challenge, mass spectrometry has been extensively applied for the identification and differentiation of various of sugar ester compounds in tobacco. However, there is no study regarding the separation and analysis of sugar esters specifically within Burley tobacco leaves. In this research, Burley tobacco leaf extracts were obtained using the solvent extraction technique, and underwent separation using silica gel column chromatography. Ultimately, the fractions comprising glucose esters and various sucrose esters were collected, respectively. The structural identification of these acquired sugar esters was achieved by liquid chromatography-tandem mass spectrometry (LC-MSn). According to the MS2 fragment ions of sucrose esters, the mass difference of 162.05 and 204.06 was mainly observed, implying an unbound fructose ring and a fructose ring acetylated in the sucrose ester, respectively. The composition information of fatty acids substituted to the glucose ring were further revealed based on the MS3 or MS2 fragment ions from sucrose esters or glucose esters. By combining the relative molecular weight, molecular formula, and the above mentioned fragment information, four types of sucrose esters from SE-I to SE-IV (referred to as compound 1-20) and two types of glucose esters GE-I to GE-II (referred to as compound 21-31) were finally identified. Among them, four sucrose esters of distinct molecular weights were newly discovered, and the structures of eight glucose esters were reported for the first time in cultivated tobacco. The sugar esters were analyzed by high-resolution mass spectrometry, which could effectively distinguish the number of fatty acids substituted on glucose and fructose, thus facilitating the differentiation of sugar ester types. Nevertheless, the identification of sugar esters in this study was limited to determine the characteristic skeleton and fatty acid composition. Detailed information on specific fatty acid types and substitution sites require further investigation using NMR technique. In conclusion, these results contribute to the current knowledge of sugar esters in Burley tobacco by expanding the range of identified types and providing high-resolution mass spectrometry data for various types of sugar esters for the first time. These findings hold significant reference value for the analysis, identification, and metabolism of different sucrose and glucose esters in tobacco.

The medium of X65 steel injection sea pipe contains dissolved oxygen, causing severe corrosion inside the pipeline. Regarding this issue, based on the basic data of the on-site water injection subsea pipeline, considering the effects of flow rate, temperature, dissolved oxygen and Cl- concentration on the corrosion behavior of X65 steel, 9 sets of orthogonal tests were designed, and the weight loss test and corrosion product characterization were carried out by using high temperature autoclave, scanning electron microscope and X-ray diffractometer. Combined with multiple linear regression method, a corrosion prediction model was established. Results showed that the order of the degree of influence of the four influencing factors on corrosion rate from large to small was: dissolved oxygen concentration > temperature > flow rate> Cl- concentration, and dissolved oxygen concentration was the main control factor of corrosion. The corrosion rate increased with the increases of flow rate, temperature, dissolved oxygen concentration and Cl- concentration. The characterization results of corrosion products showed that the corrosion products were mainly Fe3O4 and Fe2O3. Considering the influence of the above four factors, a corrosion prediction model was established based on seven groups of uniform corrosion rate values. Furthermore, the remaining two groups of uniform corrosion rate values were used to validate the corrosion prediction model, and the maximum error was 8.9%, indicating that the corrosion rate prediction model was accurate.

Abstract Aim The purpose of this study was to compare the long-term outcomes of laparoscopic hepatectomy (LH) and percutaneous radiofrequency ablation (PRFA) for the treatment of small hepatocellular carcinoma. Methods We systematically searched PubMed, Embase, Web of Science, and Medline from January 2000 to May 2022 for literature comparing the efficacy of LH and PRFA in the treatment of small hepatocellular carcinoma (largest tumour diameter ≤ 3 cm, number of intrahepatic tumours ≤3, or diameter of a single intrahepatic lesion ≤5 cm. ). We assessed overall survival (OS), recurrence-free survival (RFS), local recurrence and complication rates. Results A total of 1886 patients with small HCC were included in the 8 studies included in this study, of which 839 underwent LH and 1047 underwent PRAF. The results of the meta-analysis showed that the two groups had the same 3-year (HR: 0.99, 95% CI: 0.67 to 1.47) and 5-year (HR: 1.30, 95% CI: 0.90 to 1.87) OS rates, and the LH group had better 3-year (HR: 0.58, 95% CI: 0.49 to 0.68) and 5-year (HR: 0.56, 95% CI: 0.37 to 0.85) RFS rates. The LH group had a lower local recurrence rate (OR: 0.19, 95% CI: 0.12 to 0.32), but the PRFA group had a lower complication rate (OR: 2.49, 95% CI: 1.76 to 3.54). Conclusion There was no difference in OS between LH and PRFA in the treatment of small HCC. LH had a higher RFS rate and a lower local recurrence rate, but PRFA had a lower complication rate. In general, the long-term efficacy of LH in the treatment of small HCC is better than that of PRFA. Considering the advantages of less trauma and a low complication rate of PRFA, a large number of RCT studies are needed for further verification in the future.

Abstract (+)-Neomenthylamine is an important industrial precursor used to synthesize high value-added chemicals. Here, we report a novel biocatalytic route to synthesize (+)-neomenthylamine by amination of readily available (−)-menthone substrate using ω-transaminase. By screening a panel of ω-transaminases, an ω-transaminase from Vibrio fluvialis JS17 was identified with considerable amination activity to (−)-menthone, and then characterization of enzymatic properties was conducted for the enzyme. Under optimized conditions, 10 mM (−)-menthone was transformed in a mild aqueous phase with 4.7 mM product yielded in 24 h. The biocatalytic route using inexpensive starting materials (ketone substrate and amino donor) and mild reaction conditions represents an easy and green approach for (+)-neomenthylamine synthesis. This method underscores the potential of biocatalysts in the synthesis of unnatural terpenoid amine derivatives. Graphical Abstract