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Industrial biosynthesis of β-nicotinamide mononucleotide (β-NMN) lacks a highly active nicotinamide riboside kinase for the phosphorylation process. Cumbersome preprocessing steps and excessive ATP addition contribute to its increased cost. To tackle these challenges, a docking combination simulation (DCS) semirational mutagenesis strategy was designed in this study, combining various modification strategies to obtain a mutant NRK-TRA with 2.9-fold higher enzyme activity. Molecular dynamics simulations and structural analysis demonstrate the enhancement of its structural stability. High-density fermentation was achieved through a 5 L fermentation tank, with a titer reaching 208.3 U/mL, the highest in the current report. An ATP-cycling whole-cell catalytic system was employed and optimized by introducing a polyphosphate kinase 2 (PPK2) recombinant strain, and 15.16 g/L β-NMN was obtained through a series of batch transformation experiments. This study provides a new strategy for the efficient screening of highly active enzyme variants and offers a green and promising biotransformation system for NMN production.

Phosphatidylserine is widely used in food, health, chemical and pharmaceutical industries. The phospholipase D-mediated green synthesis of phosphatidylserine has attracted substantial attention in recent years. In this study, the phospholipase D was heterologously expressed in Bacillus subtilis, Pichia pastoris, and Corynebacterium glutamicum, respectively. The highest activity of phospholipase D was observed in C. glutamicum, which was 0.25 U/mL higher than these in B. subtilis (0.14 U/mL) and P. pastoris (0.22 U/mL). System engineering of three potential factors, including (1) signal peptides, (2) ribosome binding site, and (3) promoters, was attempted to improve the expression level of phospholipase D in C. glutamicum. The maximum phospholipase D activity reached 1.9 U/mL, which was 7.6-fold higher than that of the initial level. The enzyme displayed favorable transphosphatidylation activity and it could efficiently catalyze the substrates L-serine and soybean lecithin for synthesis of phosphatidylserine after optimizing the conversion reactions in detail. Under the optimum conditions (trichloromethane/enzyme solution 4:2, 8 mg/mL soybean lecithin, 40 mg/mL L-serine, and 15 mM CaCl 2 , with shaking under 40 °C for 10 h), the reaction process showed 48.6% of conversion rate and 1.94 g/L of accumulated phosphatidylserine concentration. The results highlight the use of heterologous expression, system engineering, and process optimization strategies to adapt a promising phospholipase D for efficient phosphatidylserine production in synthetic application.

Abstract Over the past decades, nitrilases have drawn considerable attention because of their application in nitrile degradation as prominent biocatalysts. Nitrilases are derived from bacteria, filamentous fungi, yeasts, and plants. In-depth investigations on their natural sources function mechanisms, enzyme structure, screening pathways, and biocatalytic properties have been conducted. Moreover, the immobilization, purification, gene cloning and modifications of nitrilase have been dwelt upon. Some nitrilases are used commercially as biofactories for carboxylic acids production, waste treatment, and surface modification. This critical review summarizes the current status of nitrilase research, and discusses a number of challenges and significant attempts in its further development. Nitrilase is a significant and promising biocatalyst for catalytic applications.

The nitrilase-mediated green synthesis of nicotinic acid, an important reaction in synthetic organic chemistry, has attracted considerable attention in recent years. However, the application potential of nitrilase is hindered by several limitations, such as low catalytic efficiency and byproduct formation. In this study, the site-saturation mutagenesis of asparagine 40, phenylalanine 50, and glutamine 207 in recombinant nitrilase from Pseudomonas putida CGMCC3830 was conducted to improve the specificity of nitrilase for nicotinic acid. The resulting mutants, which contain the mutations N40G (asparagine→glycine), F50W (phenylalanine→tryptophan), and Q207E (glutamine→glutamic acid), produced higher nicotinic acid yields than the wild type. Furthermore, double and triple mutations were introduced, and four mutants that contained N40G/F50W, N40G/Q207E, F50W/Q207E, and N40G/F50W/Q207E were obtained and evaluated for their capacity to produce nicotinic acid. The double mutant F50W/Q207E and the triple mutant N40G/F50W/Q207E displayed the highest activity, which was nearly twofold higher than that of the wild type. The kinetics analysis of nicotinic acid synthesis with the mutant nitrilase revealed the higher catalytic capability of all the mutants than the wild type. These results provide new insights into the catalytic performance of P. putida nitrilase toward 3-cyanopyridine to promote nicotinic acid production. [ABSTRACT FROM AUTHOR]

Nitrile-converting enzymes, including nitrilase and nitrile hydratase (NHase), have received increasing attention from researchers of industrial biocatalysis because of their critical role as a tool in organic synthesis of carboxylic acids and amides from nitriles. To date, these bioconversion approaches are considered as one of the most potential industrial processes using resting cells or purified enzymes as catalysts for production of food additives, pharmaceutical, and agrochemical precursors. This review focuses on the distribution and catalytic mechanism research of nitrile-converting enzymes in recent years. Molecular biology aspects to improve the biocatalytic performance of microbial nitrilase and NHase are demonstrated. The process developments of microbial nitrilase and NHase for organic synthesis are also discussed. [ABSTRACT FROM AUTHOR]

The constitutively expression system for P. putida nitrilase was firstly constructed to improve the nicotinic acid production and reduce the production costs. High density culture strategy was employed to enhance the biomass and nitrilase production of recombinant strain. The total nitrilase activity reached up to 654 U·mL −1 without the induction. 541 g·L −1 nicotinic acid was accumulated via fed batch mode of substrate feeding through 290 min of conversion. [ABSTRACT FROM AUTHOR]

Biotransformation of a series of steroid compounds (estradiol, estrone, androst-4-en-3,17-dione, testosterone, canrenone, 16α,17α-epoxyprogesterone and progesterone) with Colletotrichum lini ST-1 as biocatalyst was investigated. With the exception of estradiol, estrone and progesterone, the microorganism could selectively hydroxylate steroid substrates (4 g/L) with 70–85% conversion rate and 60–76% total products yield. The different hydroxylation sites between androst-4-en-3,17-dione ( 3 ) and testosterone ( 4 ) suggested that the hydroxyl group or carbonyl group on the substrate at C17 had profound influence on the location of introduced hydroxyl groups. Transformations of 3-keto-steroid ( 3 , 4 , 5 , 6 and 7 ) included monohydroxylation or dihydroxylation at 11α and 15α positions, while hydroxylations of 3-hydroxy-steroid (DHEA) were hydroxylation at 7α and 15α positions. Moreover, time course experiments demonstrated dihydroxylation of androst-4-en-3,17-dione ( 3 ), canrenone ( 5 ) and 16α,17α-epoxyprogesterone ( 6 ) were all initiated by hydroxylation on ring-D (C15) followed by attack on ring-C (C11). In this study, several new hydroxylation products were discovered, including 11α,15α-dihydroxyandrost-4-en-3,17-dione ( 9 ), 11α,15α-dihydroxy-canrenone ( 12 ) and 11α,15α-dihydroxy-16α,17α-epoxyprogesterone ( 14 ). The breadth of substrate spectrum and the excellent conversion rates achieved with this fungus indicated that C. lini ST-1 was a potential microorganism for production of valuable pharmaceutical ingredients and precursors. [ABSTRACT FROM AUTHOR]