A holistic approach for process intensification of nicotinamide mononucleotide production via high cell density cultivation under exponential feeding strategy

Metabolic reprogramming and machine learning-guided cofactor engineering to boost nicotinamide mononucleotide production in Escherichia coli

Nicotinamide mononucleotide (NMN) is a bioactive compound in NAD(P)+ metabolism, which exhibits diverse pharmaceutical interests. However, enhancing NMN biosynthesis faces the challange of competing with cell growth and disturbing intracellular redox homeostasis. Herein, we boosted NMN production in Escherichia coli by reprogramming central carbon metabolism with a machine learning (ML)-guided cofactor engineering strategy. Engnieering NMN biosynthesis-related pathway directed carbon flux toward NMN with the NADPH level increased by 73 %, which, although enhanced NMN titer (2.45 g/L), impaired cell growth. A quorum sensing (QS)-controlled cofactor engineering system was thus contructed and optimized by ML models to address redox imbalance, which led to 3.04 g/L NMN with improved cell growth. The final strain S344 produced 20.13 g/L NMN in fed-batch fermentation. This study showed that perturbation on cofactor level is a crucial limiting factor for NMN biosynthesis, and proposed a novel ML-guided strategy to manipulate intracellular redox state for efficient NMN production.

Microbial Production of Nicotinamide Mononucleotide: Key Enzymes Discovery, Host Cells Selection, and Pathways Design and Optimization

As an important bioactive substance in cells, nicotinamide mononucleotide (NMN) has been proven to play an important role in antiaging, treatment of neurodegenerative diseases, and cardioprotection. It presents a high potential for application in the research fields of functional foods, cosmetics, healthcare products, and active pharmaceuticals. With the increased demand, whether NMN can achieve large-scale industrial production has been a wide concern. The chemical synthesis method of NMN mainly faces the problems of separation, purification, and complex process control; in contrast, biosynthesis methods such as microbial fermentation and enzyme catalysis are considered to be the mainstream of the future industrial production of NMN due to the advantages of environmental friendliness, high efficiency, and simple separation. This review first describes the physiological functions of NMN and the related areas of its applications. Subsequently, it focuses on the research progress on different synthetic pathways of NMN in biosynthetic approaches, mining and modification of key enzymes, chassis cell design and optimization, and whole-cell catalysis. Meanwhile, the regulatory strategies, methods, and process control of the microbial synthesis of NMN are also elaborated, and the synthesis efficiencies of different chassis cells are systematically compared. Finally, this review summarizes the existing problems and challenges of microbial synthesis of NMN and proposes future strategies and directions to address these issues. This work provides technical references and a theoretical basis for researching efficient NMN microbial synthesis and application.

Improving Biosynthesis Efficiency of Nicotinamide Mononucleotide by ATP Recycling Engineering and Condition Optimization

Nicotinamide mononucleotide (NMN) is a very important bioactive nucleotide that is of great help to human health. However, its widespread application has been limited by its high production costs, especially the cost of the core substrates, coenzyme, and enzymes. In this study, the ADP/GDP-polyphosphate phosphotransferase RhPPK2 originating from Rhodobacter sphaeroides was successfully expressed in Escherichia coli with high-level solubility, and the enzyme activity in the lysate supernatant reached 21.9 ± 0.65 U/mL. And then, the temperature profiles, pH profiles, and kinetic parameters of purified reRhPPK2 were systematically characterized, which demonstrate its potential for application in enzymatic ATP regeneration systems. Furthermore, the introduction of reRhPPK2 for ATP regeneration significantly enhanced NMN production efficiency, achieving a 2.3-fold increase compared to the conventional ATP supplementation method. Finally, the production efficiency of NMN was further improved by a single-factor experiment and L9(34) orthogonal design, and the yield was up to 14.6 ± 0.51 g/L, about 5.4 times of the initial yield. This research substantially reduced NMN production costs and established a robust foundation for industrial-scale NMN production.

Cell-free biocatalysis for co-production of nicotinamide mononucleotide and ethanol from Saccharomyces cerevisiae and recombinant Escherichia coli

Cell-free enzyme systems have emerged as a promising approach for producing various biometabolites, offering several advantages over traditional whole-cell systems. This study presents an approach to producing nicotinamide mononucleotide (NMN) by combining a Saccharomyces cerevisiae cell-free enzyme with a recombinant Escherichia coli cell-free enzyme. The system leverages the ATP generated by yeast during ethanol fermentation to produce NMN in the presence of nicotinamide (NAM) as a substrate. The optimal cell-free enzyme concentration and substrate concentration were investigated to maximize NMN production. The results showed that combined cell-free enzymes led to increased NMN and ethanol yields, with a maximum production of 1.5 mM NMN (2.7-fold) and ethanol production of 0.45 g/L achieved (1.6-fold) compared to individual cell-free enzymes. Furthermore, the study demonstrated that the protein concentration affected NMN production, with optimal production achieved at 5 g/L. This study demonstrates the potential of integrating multiple metabolic pathways in a single cell-free system, paving the way for the development of more efficient and sustainable bioproduction processes.

Harnessing lactic acid bacteria for nicotinamide mononucleotide biosynthesis: a review of strategies and future directions

Nicotinamide mononucleotide (NMN), one of the crucial precursors of nicotinamide adenine dinucleotide, has garnered considerable interest for its pharmacological and anti-aging effects, conferring potential health and economic benefits for humans. Lactic acid bacteria (LAB) are one of the most important probiotics, which is commonly used in the dairy industry. Due to its probiotic properties, it presents an attractive platform for food-grade NMN production. LAB have also been extensively utilized to enhance the functional properties of pharmaceuticals and cosmetics, making them promising candidates for large-scale up synthesis of NMN. This review provides an in-depth analysis of various metabolic engineering strategies, including enzyme optimization, pathway rewiring, and fermentation process enhancements, to increase NMN yields in LAB. It explores both CRISPR/Cas9 and traditional methods to manipulate key biosynthetic pathways. In particular, this study discussed future research directions, emphasizing the application of synthetic biology, systems biology, and AI-driven optimization to further enhance NMN production. It provides invaluable insights into developing scalable and industrially relevant processes for NMN production to meet the growing market demand.

Biosynthesis of Nicotinamide Mononucleotide: Synthesis Method, Enzyme, and Biocatalytic System

Nicotinamide mononucleotide (NMN) has garnered substantial interest as a functional food product. Industrial NMN production relies on chemical methods, facing challenges in separation, purification, and regulatory complexities, leading to elevated prices. In contrast, NMN biosynthesis through fermentation or enzyme catalysis offers notable benefits like eco-friendliness, recyclability, and efficiency, positioning it as a primary avenue for future NMN synthesis. Enzymatic NMN synthesis encompasses the nicotinamide-initial route and nicotinamide ribose-initial routes. Key among these is nicotinamide riboside kinase (NRK), pivotal in the latter route. The NRK-mediated biosynthesis is emerging as a prominent trend due to its streamlined route, simplicity, and precise specificity. The essential aspect is to obtain an engineered NRK that exhibits elevated activity and robust stability. This review comprehensively assesses diverse NMN synthesis methods, offering valuable insights into efficient, sustainable, and economical production routes. It spotlights the emerging NRK-mediated biosynthesis pathway and its significance. The establishment of an adenosine triphosphate (ATP) regeneration system plays a pivotal role in enhancing NMN synthesis efficiency through NRK-catalyzed routes. The review aims to be a reference for researchers developing green and sustainable NMN synthesis, as well as those optimizing NMN production.

Improvement of an enzymatic cascade synthesis of nicotinamide mononucleotide via protein engineering and reaction-process reinforcement

Enzymatic synthesis of β-nicotinamide mononucleotide (NMN) from D-ribose has garnered widespread attention due to its cheap material, the use of mild reaction conditions, and the ability to produce highly pure products with the desired optical properties. However, the overall NMN yield of this method is impeded by the low activity of rate-limiting enzymes. The ribose-phosphate diphosphokinase (PRS) and nicotinamide phosphoribosyltransferase (NAMPT), that control the rate of the reaction, were engineered to improve the reaction efficacy. The actives of mutants PRS-H150Q and NAMPT-Y15S were 334% and 57% higher than that of their corresponding wild-type enzymes, respectively. Furthermore, by adding pyrophosphatase, the byproduct pyrophosphate which can inhibit the activity of NAMPT was degraded, leading to a 6.72% increase in NMN yield. Following with reaction-process reinforcement, a high yield of 8.10 g L-1 NMN was obtained after 3 h of reaction, which was 56.86-fold higher than that of the stepwise reaction synthesis (0.14 g L-1 ), indicating that the in vitro enzymatic synthesis of NMN from D-ribose and niacinamide is an economical and feasible route.