Extraction, purification and identification of menaquinones from Flavobacterium meningosepticum fermentation medium

Insights into Regulating Mechanism of Mutagenesis Strains of Elizabethkingia meningoseptica sp. F2 by Omics Analysis

Vitamin K₂ plays an important role in electron transport, blood coagulation, and calcium homeostasis, and researchers have been trying to use microbes to produce it. Although our previous studies have shown that gradient radiation, breeding, and culture acclimation can improve vitamin K₂ production in Elizabethkingia meningoseptica, the mechanism is still unclear. This study is the first which performs genome sequencing of E. meningoseptica sp. F2 as a basis for subsequent experiments and further comparative analyses with other strains. Comparative metabolic pathway analysis of E. meningoseptica sp. F2, E. coli, Bacillus subtilis, and other vitamin K₂ product strains revealed that the mevalonate pathway of E. meningoseptica sp. F2 is different in bacteria at the system level. The expressions of menA, menD, menH, and menI in the menaquinone pathway and idi, hmgR, and ggpps in the mevalonate pathway were higher than those in the original strain. A total of 67 differentially expressed proteins involved in the oxidative phosphorylation metabolic pathway and citric acid cycle (TCA cycle) were identified. Our results reveal that combined gradient radiation breeding and culture acclimation can promote vitamin K₂ accumulation probably by regulating the vitamin K₂ pathway, oxidative phosphorylation metabolism pathway, and the citrate cycle (TCA cycle).

Biotechnological production and application of epsilon-poly-L-lysine (ε-PL): biosynthesis and its metabolic regulation

Epsilon-poly-L-lysine (ε-PL) is an unusual biopolymer composed of L-lysine produced by several microorganisms, especially by the genus Streptomyces. Due to its excellent antimicrobial activity, good water solubility, high safety, and biodegradable nature, ε-PL with a GRAS status has been widely used in food and pharmaceutical industries. In the past years, studies have focused on the biotechnological production of ɛ-PL, the biosynthetic mechanism of microbial ɛ-PL, and its application. To provide new perspectives from recent advances, the review introduced the methods for the isolation of ɛ-PL producing strains and the biosynthetic mechanism of microbial ɛ-PL. We summarized the strategies for the improvement of ɛ-PL producing strains, including physical and chemical mutagenesis, ribosome engineering and gene engineering, and compared the different metabolic regulation strategies for improving ɛ-PL production, including medium optimization, nutrient supply, pH control, and dissolved oxygen control. Then, the downstream purification methods of ɛ-PL and its recent applications in food and medicine industries were introduced. Finally, we also proposed the potential challenges and the perspectives for the production of ε-PL.

Engineering microbial consortia of Elizabethkingia meningoseptica and Escherichia coli strains for the biosynthesis of vitamin K2

Background

The study and application of microbial consortia are topics of interest in the fields of metabolic engineering and synthetic biology. In this study, we report the design and optimisation of Elizabethkingia meningoseptica and Escherichia coli co-culture, which bypass certain limitations found during the molecular modification of E. meningoseptica, such as resistance to many antibiotics and fewer available molecular tools.

Results

The octaprenyl pyrophosphate synthase from E. meningoseptica sp. F2 (EmOPPS) was expressed, purified, and identified in the present study. Then, owing to the low vitamin K2 production by E. coli or E. meningoseptica sp. F2 monoculture, we introduced the E. meningoseptica and E. coli co-culture strategy to improve vitamin K2 biosynthesis. We achieved production titres of 32 mg/L by introducing vitamin K2 synthesis-related genes from E. meningoseptica sp. F2 into E. coli, which were approximately three-fold more than the titre achieved with E. meningoseptica sp. F2 monoculture. This study establishes a foundation for further engineering of MK-n (n = 4, 5, 6, 7, 8) in a co-cultivation system of E. meningoseptica and E. coli. Finally, we analysed the surface morphology, esterase activity, and membrane permeability of these microbial consortia using scanning electron microscopy, confocal laser scanning microscopy, and flow cytometry, respectively. The results showed that the co-cultured bacteria were closely linked and that lipase activity and membrane permeability improved, which may be conducive to the exchange of substances between bacteria.

Conclusions

Our results demonstrated that co-culture engineering can be a useful method in the broad field of metabolic engineering of strains with restricted molecular modifications.

Production of Vitamin K by Wild-Type and Engineered Microorganisms

Vitamin K is a fat-soluble vitamin that mainly exists as phylloquinone or menaquinone in nature. Vitamin K plays an important role in blood clotting and bone health in humans. For use as a nutraceutical, vitamin K is produced by natural extraction, chemical synthesis, and microbial fermentation. Natural extraction and chemical synthesis methods for vitamin K production have limitations, such as low yield of products and environmental concerns. Microbial fermentation is a more sustainable process for industrial production of natural vitamin K than two other methods. Recent advanced genetic technology facilitates industrial production of vitamin K by increasing the yield and productivity of microbial host strains. This review covers (i) general information about vitamin K and microbial host, (ii) current titers of vitamin K produced by wild-type microorganisms, and (iii) vitamin K production by engineered microorganisms, including the details of strain engineering strategies. Finally, current limitations and future directions for microbial production of vitamin K are also discussed.

Cloning and functional characterization of the geranylgeranyl diphosphate synthase(GGPPS)from Elizabethkingia meningoseptica sp.F2

To date, there is no functional characterization of EmGGPPS (from Elizabethkingia meningoseptica sp.F2) as enzymes catalyzing GGPP. In this research, maltose-binding protein (MBP), disulfide bond A (DbsA), disulfide bond C (DbsC), and two other small protein tags, GB1 (Protein G B1 domain) and ZZ (Protein A IgG ZZ repeat domain), were used as fusion partners to construct an EmGGPPS fusion expression system. The results indicated that the expression of MBP-EmGGPPS was higher than that of the other four fusion proteins in E. coli BL21 (DE3). Additionally, using EmGGPPS as a catalyst for the production of GGPP was verified using a color complementation assay in Escherichia coli. In parallel with it, the enzyme activity experiment in vitro showed that the EmGGPPS protein could produce GGPP, GPP and FPP. Finally, we successfully demonstrated MK-4 production in engineered E. coli by overexpression of EmGGPPS.

Epsilon-poly-L-lysine: Recent Advances in Biomanufacturing and Applications

ε-poly-L-lysine (ε-PL) is a naturally occurring poly(amino acid) of varying polymerization degree, which possesses excellent antimicrobial activity and has been widely used in food and pharmaceutical industries. To provide new perspectives from recent advances, this review compares several conventional and advanced strategies for the discovery of wild strains and development of high-producing strains, including isolation and culture-based traditional methods as well as genome mining and directed evolution. We also summarize process engineering approaches for improving production, including optimization of environmental conditions and utilization of industrial waste. Then, efficient downstream purification methods are described, including their drawbacks, followed by the brief introductions of proposed antimicrobial mechanisms of ε-PL and its recent applications. Finally, we discuss persistent challenges and future perspectives for the commercialization of ε-PL.

Combining mutagenesis on Glu281 of prenyltransferase NovQ and metabolic engineering strategies for the increased prenylated activity towards menadione

Prenyltransferase NovQ is a vital class involved in the biosynthesis of secondary metabolites such as clorobiocin and novobiocin. To investigate the relationship between structure and catalytic properties of NovQ, here, we have analyzed the substrate-binding site, namely PT barrel, and revealed that menadione hydroquinol formed intermolecular interactions with the residue Glu281 near the center of the active pocket. In this study, Glu281 was substituted with 9 diverse amino acids and catalytic properties of mutants were observed in vitro. Among them, E281Q showed 2.05-fold activities towards the aromatic substrate and prenyl donor, while others obtained catalytic efficiency between 8.4 and 88.6% of that of wild-type NovQ. Furthermore, the effects of catalytic conditions and substrate status on the activity of NovQ and its mutants were considered to obtain the optimized prenylated reaction. When the evolutionary NovQ variant E281Q was overexpressed in the host constructed to synthesize dimethylallyl diphosphate through the engineered mevalonate (MVA) pathway, we harvested up to 4.7 mg/L prenylated menadione at C-3 position by exogenously supplying the aromatic substrate. The construction of the microbial platform based on NovQ opens a new orientation to further biosynthesize various vitamin K₂ with other ABBA prenyltransferases in E. coli.

Microbial production of vitamin K2: current status and future prospects

Vitamin K2, also called menaquinone, is an essential lipid-soluble vitamin that plays a critical role in blood clotting and prevention of osteoporosis. It has become a focus of research in recent years and has been widely used in the food and pharmaceutical industries. This review will briefly introduce the functions and applications of vitamin K2 first, after which the biosynthesis pathways and enzymes will be analyzed in-depth to highlight the bottlenecks facing the microbial vitamin K2 production on the industrial scale. Then, various strategies, including strain mutagenesis and genetic modification, different cultivation modes, fermentation and separation processes, will be summarized and discussed. The future prospects and perspectives of microbial menaquinone production will also be discussed finally.

Biofilm reactors as a promising method for vitamin K (menaquinone-7) production

Menaquinone-7 (MK-7) is the most potent subtype of vitamin K with extraordinarily high half-life in the circulatory system. Therefore, MK-7 plays a critical role in promoting human wellbeing today. Studies on MK-7 every year show more and more magnificent benefits of it in preventing cardiovascular diseases and osteoporosis to battling cancer cells, Alzheimer's and Parkinson's diseases. Thus, it needs to be supplemented to daily diet for accumulative and long-term benefits. Chemical synthesis of MK-7 produces a significant cis-isomer form of it, which has no biological activity. Fortunately, due to its key role in electron transfer in bacteria, trans-MK-7 is biosynthesized by especially Gram-positive strains mainly Bacillus genus. Concordantly, MK-7 could be produced via solid or liquid state fermentation strategies. In either regime, when static fermentation is applied in the absence of agitation and aeration, operational issues arise such as heat and mass transfer inefficiencies. Thus, scaling up the process becomes a challenge. On the other hand, studies have indicated that biofilm and pellicle formation that occur in static fermentations are key characteristics for extracellular MK-7 secretion. Therefore, this review covers the most recent discoveries of the therapeutic properties of MK-7 and optimization attempts at increasing its biosynthesis in different media compositions and effective growth parameters as well as the cutting-edge use of biofilm reactors where B. subtilis cells have the infrastructures to form mature biofilm formations on plastic composite supports. Biofilm reactors therefore can provide robust extracellular MK-7 secretion while simultaneously enduring high agitation and aeration rates, which then address the scale-up and operational issues associated with static fermentation strategies.

Characterization of MK₈(H₂) from Rhodococcus sp. B7740 and Its Potential Antiglycation Capacity Measurements

Menaquinone (MK) has an important role in human metabolism as an essential vitamin (VK₂), which is mainly produced through the fermentation of microorganisms. MK₈(H₂) was identified to be the main menaquinone from Rhodococcus sp. B7740, a bacterium isolated from the arctic ocean. In this work, MK₈(H₂) (purity: 99.75%) was collected through a convenient and economic extraction process followed by high-speed countercurrent chromatography (HSCCC) purification. Additionally, high-resolution mass spectrometry (HRMS) was performed for further identification and the hydrogenation position of MK₈(H₂) (terminal unit) was determined using nuclear magnetic resonance (NMR) for the first time. MK₈(H₂) showed a superior antioxidant effect and antiglycation capacity compared with ubiquinone Q10 and MK₄. High-performance liquid chromatography–mass spectrometer (HPLC-MS/MS) and molecular docking showed the fine interaction between MK₈(H₂) with methylglyoxal (MGO) and bull serum albumin (BSA), respectively. These properties make MK₈(H₂) a promising natural active ingredient with future food and medicine applications.