Search Results (2)

Chiral dimethyl 2-methylsuccinate (1) is a very important building block for the manufacturing of many active pharmaceutical ingredients and fine chemicals. The asymmetric reduction of C=C double bond of dimethyl citraconate (2), dimethyl mesaconate (3) or dimethyl itaconate (4) by ene-reductases (ERs) represents an attractive straightforward approach, but lack of high-performance ERs, especially (S)-selective ones, has limited implementing this method to prepare the optically pure dimethyl 2-methylsuccinate. Herein, three ERs (Bac-OYE1 from Bacillus sp., SeER from Saccharomyces eubayanus and AfER from Aspergillus flavus) with high substrate tolerance and stereoselectivity towards 2, 3 and 4 have been identified. Up to 500 mM of 3 was converted to (S)-dimethyl 2-methylsuccinate ((S)-1) by SeER in high yields (80%) and enantioselectivity (98% ee), and 700 mM of 2 and 400 mM of 4 were converted to (R)-1 by Bac-OYE1 and AfER, respectively, in high yields (86% and 77%) with excellent enantioselectivity (99% ee). The reductions of diethyl citraconate (5), diethyl mesaconate (6) and diethyl itaconate (7) were also tested with the three ERs. Although up to 500 mM of 5 was completely converted to (R)-diethyl 2-methylsuccinate ((R)-8) by Bac-OYE1 with excellent enantioselectivity (99% ee), the alcohol moiety of the esters had a great effect on the activity and enantioselectivity of ERs. This work provides an efficient methodology for the enantiocomplementary production of optically pure dimethyl 2-methylsuccinate from dimethyl itaconate and its isomers at high titer. Full article

Nitrite (NIT), a commonly used food additive, especially in pickled and cured vegetables and meat products, might cause acute and chronic diseases. Fermentation with lactic acid bacteria (LAB) is an effective method for degrading NIT and improving the flavor of pickled and cured foods. In this study, Limosilactobacillus fermentum (L. fermentum) RC4 with a high NIT degradation ability was found to degrade NIT in a new manner when compared with reported enzymatic and acid degradation, namely, metabolite degradation during fermentation in MRS broth, which shows a synergistic effect with acid to increase NIT degradation. Liquid chromatography–mass spectrometry analysis identified 134 significantly different metabolites, of which 11 metabolites of L. fermentum RC4, namely, γ-aminobutyric acid (GABA), isocitric acid, D-glucose, 3-methylthiopropionic acid (MTP), N-formyl-L-methionine, dimethyl sulfone (MSM), D-ribose, mesaconate, trans-aconitic acid, L-lysine, and carnosine, showed significant NIT degradation effects compared with the control group (MRS broth). Verification experiments showed that adding the above 11 metabolites to 100 mg/L NIT and incubating for 24 h resulted in NIT degradation rates of 5.07%, 4.41%, 6.08%, 16.93%, 5.28%, 2.41%, 0.93%, 18.93%, 12.25%, 6.42%, and 3.21%, respectively. Among these, three metabolites, namely, mesaconate, MTP, and trans-aconitic acid, showed efficient NIT degradation abilities that might be related to the degradation mechanism involving decarboxylation reactions. This is the first systematic study of NIT degradation by LAB, resulting in the identification of a new metabolite degradation pathway and three efficient NIT degradation metabolites. Full article