Constitutive expression of nitrilase from Rhodococcus zopfii for efficient biosynthesis of 2-chloronicotinic acid

2-chloronicotinic acid (2-CA) is a key precursor for the synthesis of a series of pesticides and pharmaceuticals. Nitrilase-catalyzed bioprocess is a promising method for 2-CA production from 2-chloronicotinonitrile (2-CN). In this study, a mutant of nitrilase from Rhodococcus zopfii (RzNIT/W167G) was constitutively overexpressed with Escherichia coli as host, which exhibited a onefold increase in enzymatic activity compared with inducible expression. Biosynthesis of 2-CA using whole cells harboring nitrilase as biocatalysts were investigated and 318.5 mM 2-CA was produced, which was the highest level for 2-CA production catalyzed by nitrilase to date. 2-CA was recovered from the reaction mixture through a simple acidification step with a recovery yield of 90%. This study developed an efficient bioprocess for 2-CA with great potential for industrial application.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-022-03119-0.

Synthesis of chiral β-substituted γ-amino-butyric acid derivatives via enantioconvergent ring opening of racemic 2-(hetero)aryl aziridines with ketene silyl acetals

Lewis acid-catalyzed enantioconvergent ring opening of racemic 2-(hetero)aryl-N-sulfonyl aziridines with ketene silyl acetals is developed.

Structure-guided protein engineering of ammonia lyase for efficient synthesis of sterically bulky unnatural amino acids

Enzymatic asymmetric amination addition is seen as a promising approach for synthesizing amine derivatives, especially unnatural amino acids, which are valuable precursors to fine chemicals and drugs. Despite the broad substrate spectrum of methylaspartate lyase (MAL), some bulky substrates, such as caffeic acid, cannot be effectively accepted. Herein, we report a group of variants structurally derived from Escherichia coli O157:H7 MAL (EcMAL). A combined mutagenesis strategy was used to simultaneously redesign the key residues of the entrance tunnel and binding pocket to explore the possibility of accepting bulky substrates with potential application to chiral drug synthesis. Libraries of residues capable of lining the active center of EcMAL were then constructed and screened by an effective activity solid-phase color screening method using tyrosinase as a cascade catalyst system. Activity assays and molecular dynamics studies of the resultant variants showed that the substrate specificity of EcMAL was modified by adjusting the polarity of the binding pocket and the degree of flexibility of the entrance tunnel. Compared to M3, the optimal variant M8 was obtained with a 15-fold increase in catalytic activity. This structure-based protein engineering of EcMAL can be used to open new application directions or to develop practical multi-enzymatic processes for the production of various useful compounds.

Biocatalysis: Enzymatic Synthesis for Industrial Applications

Biocatalysis has found numerous applications in various fields as an alternative to chemical catalysis. The use of enzymes in organic synthesis, especially to make chiral compounds for pharmaceuticals as well for the flavors and fragrance industry, are the most prominent examples. In addition, biocatalysts are used on a large scale to make specialty and even bulk chemicals. This review intends to give illustrative examples in this field with a special focus on scalable chemical production using enzymes. It also discusses the opportunities and limitations of enzymatic syntheses using distinct examples and provides an outlook on emerging enzyme classes.

Engineering a diaphorase via directed evolution for enzymatic biofuel cell application

Background

Diaphorase (DI) has received wide attention as the key anodic enzyme mediating the electron transfer and electric energy generation in enzymatic biofuel cells (EBFCs). Lowering the anodic pH may be a useful strategy for constructing high-performance in EBFCs. However, most DI suffered from the poor activity at low pHs. Therefore, it is necessary to modify the activity and its acidic tolerance to further improve the performance of the EBFC.

Results

This paper attempts to improve the enzyme activity of DI originated from Geobacillus stearothermophilus under acidic conditions through directed evolution. Three rounds of random mutagenesis by error-prone PCR of the GsDI gene followed by high-throughput screening allowed the identification of the mutant 3–8 (H37Q, S73T, F105L, S68T, G61S, D74V) exhibiting a 4- or 7-fold increase in the catalytic activity at pH 5.4 or 4.5 compared to that of the wild type. And the pH stability of mutant 3–8 was significantly better than that of wild type and showed a 1.3 times higher in the stability at pH 5.4. The EBFC anode equipped with 0.5 mg of mutant 3–8 achieved a maximum current of 40 μA at pH 5.4, much higher than that with the same loading of the wild type enzyme.

Conclusion

The GsDI has been improved in the specific activity and pH stability by directed evolution which leads to the improvement of the EBFC performance. Also, the enlarged catalytic channel of mutant and decreased B-factor may be beneficial for the activity and stability. These results suggest that this engineered DI will be a useful candidate for the construction of enhanced EBFCs.