Vitreoscilla hemoglobin enhances the catalytic performance of industrial oxidases in vitro.

Oxidases are a group of oxidoreductases and need molecular oxygen in the catalytic process. Vitreoscilla hemoglobin (VHb) can improve the growth and productivity of host cells under hypoxic conditions, rendering it attractive for industrial application. In this work, we demonstrated the addition of immobilized VHb increased the catalytic activity of immobilized D-amino acid oxidase of Trigonopsis variabilis by two-fold when catalyzing cephalosporin C under oxygen-limited conditions. A similar increase of activities was observed in glucose oxidase, alcohol oxidase, and p-hydroxymandelate synthase by adding free VHb or immobilized VHb under hypoxic conditions. When L-glutamate oxidase was used to catalyze L-glutamate to produce α-ketoglutarate, the yield increased from 80.6 to 96.9% by fusing VHb with L-glutamate oxidase. Results demonstrated that the addition of free VHb, immobilized VHb, or fused VHb could increase the catalytic efficiency of oxidases, which was considered by increasing the concentration of the microenvironmental oxygen. Thus, VHb may become a potential additive agent to promote the efficiency of oxidases on industrial scale . KEY POINTS: • First time confirmation of facilitation of VHb on several industrial oxidases in vitro • VHb functions under hypoxic conditions rather than oxygen-enriched conditions • VHb functions in vitro in the form of free, immobilized protein and fusion enzyme.

A dermocosmetic formulation containing Vichy volcanic mineralizing water, Vitreoscilla filiformis extract, niacinamide, hyaluronic acid, and vitamin E regenerates and repairs acutely stressed skin.

The exposome has an impact on skin from life-long exposure. Acute short-term exposure to exposome stressors can also alter skin functions such as skin physical barrier and immune defenses, leading to skin dryness, sensitivity, flares of inflammatory skin conditions, or viral reactivations. Probiotics are defined as live microorganisms, which, when administered in adequate amounts, confer a health benefit on the host. An extract produced by lysing Vitreoscilla filiformis (VfeV) cultured in Vichy volcanic mineralizing water (VVMW) has properties of probiotic fractions. In this review, we present in vivo and ex vivo studies with a dermocosmetic formulation containing 80% VVMW, 5% VfeV, 4% niacinamide (vitamin B3), 0.4% hyaluronic acid, and 0.2% vitamin E (M89PF) to evaluate the clinical efficacy in preventing and repairing stressed skin. Skin barrier benefits of M89PF were shown in studies after the skin was exposed to sudden thermal changes, after skin irritation by tape stripping, and in sleep-deprived women. M89PF significantly accelerated skin renewal compared to untreated skin. Skin antioxidant defense activity of M89PF was shown after exposure to stress from UVA plus cigarette smoke aggression. Skin microbiome recovery after acute stress from a harsh cleanser was significantly better in M89PF-treated skin compared to bare skin. Clinical benefits of M89PF on correcting clinical signs of stressed skin were shown in both Caucasian and Asian women exposed to a stressful lifestyle and various external (pollution, tobacco smoking, solar radiation) and internal (poor sleep, stressful work, unbalanced diet, and alcohol consumption) exposome factors. M89PF also showed depigmenting properties on dark spots in Asian women. Further clinical studies are now warranted to evaluate the efficacy of M89PF as adjuvant care to prevent and repair skin barrier disruption and reinforce skin defenses in skin exposed to acute stresses.

A combination of Vitreoscilla filiformis extract and Vichy volcanic mineralizing water strengthens the skin defenses and skin barrier.

Probiotics are live microorganisms, which, when administered in adequate amounts, confer a health benefit on the host. Semiactive, non-replicating bacteria or extracts used in dermocosmetics have interesting properties for skin quality. Vitreoscilla filiformis is cultured by a fermentation process to obtain an extract. It is considered as a probiotic fraction and topical application of this extract has shown activity to strengthen the skin physical barrier function and maintain good homeostasis of skin defenses. Vichy volcanic mineralizing water (VVMW) is a pure, highly mineralized water that has been shown to strengthen the skin against exposome aggressions. This manuscript reviews properties of probiotic fractions used in skin care, especially studies on an extract of V. filiformis grown in a medium containing VVMW (VfeV) and evaluated in combination with VVMW. Skin barrier function: In normal human epidermal keratinocyte cultures, the combination of 10% VVMW and 0.002% VfeV significantly increased transglutaminase, filaggrin, involucrin, claudin-1, and zonula occludens-1 in comparison with the controls. Antimicrobial peptide defenses: The combination of 16.7% VVMW and 0.1% VfeV increased the expression of ß-defensin-4A and S100A7. Skin immune defense functions: In lipopolysaccharide-stimulated peripheral blood mononuclear cells, the combination of 16.7% VVMW and 0.1% VfeV down-regulated IL-8, TNF-α, IL-12/IL-23p40, and increased IL10 and IL-10/IL-12 ratio compared to the control. Additionally, the combination of 79% VVMW plus 5% VfeV protected Langerhans cells in skin explants exposed to ultraviolet radiation. In conclusion, the combination of VfeV plus VVMW has properties to strengthen the skin barrier by stimulating skin differentiation and tight junctions, biochemical defenses by stimulating antimicrobial peptides, and cellular immune defenses by increasing the IL-10/IL-12 ratio and by protecting Langerhans cells challenged by ultraviolet radiation.

Production of vitamin A and vitamin E: expression of vitreoscilla hemoglobin gene in Erwinia herbicola.

Vitamin A prevents eye problems, blindness and skin problems by strengthening the immune system. Vitamin E is a nutrient that has important roles in many areas such as skin health, eye health and hormonal order. Vitreoscilla hemoglobin (VHb) gives an advantage in later phases of grown conditions to cells. In this study, the intracellular and extracellular production of vitamin A and E in E. herbicola and its recombinant strains (vgb- and vgb+) in the three different M9 mediums with supplemented 0.1% glucose, 0.1% fructose and 0.1% sucrose was investigated. Additionally, the viable cell number and total cell mass (OD600) were measured by the host and the recombinant bacteria in these mediums. The VHb gene expression in E. herbicola enhanced vitamin A under different carbon conditionals. Especially, in the vgb + strain (carrying vgb gene) the production of total vitamin in 0.1% glucose medium was recorded as 0.14 µg/ml, while the production in fructose and sucrose media was recorded as 0.07 µg/ml. The production of intracellular vitamin E in the host strain (0.025 µg/ml) was about 13-fold (0.002 µg/ml) higher than vgb + recombinant strain in 0.1% fructose. The vgb + strain showed about 2-fold higher extracellular vitamin E production than the host strain.

Vitreoscilla massiliensis sp. nov., Isolated From the Stool of an Amazonian Patient.

Strain SN6T is a non-motile and non-spore-forming gram-negative bacterium which was isolated from the stool sample of an Amazonian patient. The optimum growth was observed at 37 °C, pH 7, and 0-5 g/l of NaCl. Based on the 16S rRNA gene sequence similarity, the strain SN6T exhibited 97.5% identity with Vitreoscilla stercoraria strain ATCC_15218 (L06174), the phylogenetically closest species with standing in nomenclature. The predominant fatty acid was hexadecenoic acid (31%). The genomic DNA G + C content of the strain SN6T was 49.4 mol %. After analysis of taxonogenomic data, phenotypic and biochemical characteristics, we concluded that strain SN6T represents a new species of the genus Vitreoscilla for which the name Vitreoscilla massiliensis sp.nov is proposed. The type strain is SN6T (=CSUR P2036 = LN870312 = DSM 100958).

Combining co-culturing of Paenibacillus strains and Vitreoscilla hemoglobin expression as a strategy to improve biodesulfurization.

Enhancement of the desulfurization activities of Paenibacillus strains 32O-W and 32O-Y were investigated using dibenzothiophene (DBT) and DBT sulfone (DBTS) as sources of sulphur in growth experiments. Strains 32O-W, 32O-Y and their co-culture (32O-W plus 32O-Y), and Vitreoscilla hemoglobin (VHb) expressing recombinant strain 32O-Yvgb and its co-culture with strain 32O-W were grown at varying concentrations (0·1-2 mmol l-1 ) of DBT or DBTS for 96 h, and desulfurization measured by production of 2-hydroxybiphenyl (2-HBP) and disappearance of DBT or DBTS. Of the four cultures grown with DBT as sulphur source, the best growth occurred for the 32O-Yvgb plus 32O-W co-culture at 0·1 and 0·5 mmol l-1 DBT. Although the presence of vgb provided no consistent advantage regarding growth on DBTS, strain 32O-W, as predicted by previous work, was shown to contain a partial 4S desulfurization pathway allowing it to metabolize this 4S pathway intermediate.

Vitreoscilla filiformis Extract for Topical Skin Care: A Review.

The term probiotic has been defined by experts as live microorganisms, which when administered in adequate amounts, confer a health benefit on the host. Probiotics are, thus, by definition, live microorganisms, and the viability of probiotics is a prerequisite for certain benefits, such as the release of metabolites at the site or adhesion properties, for example. However, some semi-active or non-replicative bacterial preparations may retain a similar activity to the live forms. On cosmetic, lysates or fractions are generally used. Topically applied Vitreoscilla filiformis extract has shown to have some similar biological activity of probiotics in the gut, for example, regulating immunity by optimisation of regulatory cell function, protecting against infection, and helping skin barrier function for better recovery and resistance. Due to their mode of action and efficacy, V. filiformis extract (lysate including membrane and cytosol) may be considered as non-replicative probiotic fractions, and this review article presents all its properties.

Heterologous overexpression of bacterial hemoglobin VHb improves erythritol biosynthesis by yeast Yarrowia lipolytica.

BACKGROUND: Yarrowia lipolytica is an unconventional yeast with a huge industrial potential. Despite many advantages for biotechnological applications, it possesses enormous demand for oxygen, which is a bottleneck in large scale production. In this study a codon optimized bacterial hemoglobin from Vitreoscilla stercoraria (VHb) was overexpressed in Y. lipolytica for efficient growth and erythritol synthesis from glycerol in low-oxygen conditions. Erythritol is a natural sweetener produced by Y. lipolytica under high osmotic pressure and at low pH, and this process requires high oxygen demand. RESULTS: Under these conditions the VHb overexpressing strain showed mostly yeast-type cells resulting in 83% higher erythritol titer in shake-flask experiments. During a bioreactor study the engineered strain showed higher erythritol productivity (QERY = 0.38 g/l h) and yield (YERY = 0.37 g/g) in comparison to the control strain (QERY = 0.30 g/l h, YERY = 0.29 g/g). Moreover, low stirring during the fermentation process resulted in modest foam formation. CONCLUSIONS: This study showed that overexpression of VHb in Y. lipolytica allows for dynamic growth and efficient production of a value-added product from a low-value substrate.

Design of a microaerobically inducible replicon for high-yield plasmid DNA production.

A pUC-derived replicon inducible by oxygen limitation was designed and tested in fed-batch cultures of Escherichia coli. It included the addition of a second inducible copy of rnaII, the positive replication control element. The rnaII gene was expressed from Ptrc and cloned into pUC18 to test the hypothesis that the ratio of the positive control molecule RNAII to the negative control element, RNAI, was the determinant of plasmid copy number per chromosome (PCN). The construct was evaluated in several E. coli strains. Evaluations of the RNAII/RNAI ratio, PCN and plasmid yield normalized to biomass (YpDNA/X ) were performed and the initial hypothesis was probed. Furthermore, in high cell-density cultures in shake flasks, an outstanding amount of 126 mg/L of plasmid was produced. The microaerobically inducible plasmid was obtained by cloning the rnaII gene under the control of the oxygen-responsive Vitreoscilla stercoraria hemoglobin promoter. For this plasmid, but not for pUC18, the RNAII/RNAI ratio, PCN and YpDNA/X efficiently increased after the shift to the microaerobic regime in fed-batch cultures in a 1 L bioreactor. The YpDNA/X of the inducible plasmid reached 12 mg/g at the end of the fed-batch but the original pUC18 only reached ca. 6 mg/g. The proposed plasmid is a valuable alternative for the operation and scale-up of plasmid DNA production processes in which mass transfer limitations will not represent an issue.

Promotion of the growth and plant biomass degrading enzymes production in solid-state cultures of Lentinula edodes expressing Vitreoscilla hemoglobin gene.

Vitreoscilla hemoglobin (VHb), encoded by the Vitreoscilla hemoglobin gene (vgb), is highly effective at binding oxygen and delivering it to both prokaryotes and eukaryotes under hypoxic conditions. In this study, we introduced the vgb gene into shiitake mushrooms, and the mycelia of the transformatants grew faster. In particular, they spread into the solid substrate located in the lower part of the test tubes and bags where the oxygen was hypoxic and produced more ß-glucan and plant biomass degrading enzymes compared to the original strain. The maximum growth rate of the transformants was 8.5%-15.9% higher than that of the original strain on sawdust-based cultures in plastic bags. The laccase and amylase activities were 17.7%-40.3% and 16.7%-37.9% higher than that of the original strain, respectively. In addition, the ß-glucan contents of the transformant mycelia from the submerged fermentation were 12.9%-24.0% higher than that of the original strain. These results reveal that the expression of VHb in mushroom fungi promots the mycelial growth in solid-state cultures under the hypoxic condition as well as enhances ß-glucan and plant biomass degrading enzymes production.

The proton pumping bo oxidase from Vitreoscilla.

The cytochrome bo3 quinol oxidase from Vitreoscilla (vbo3) catalyses oxidation of ubiquinol and reduction of O2 to H2O. Data from earlier studies suggested that the free energy released in this reaction is used to pump sodium ions instead of protons across a membrane. Here, we have studied the functional properties of heterologously expressed vbo3 with a variety of methods. (i) Following oxygen consumption with a Clark-type electrode, we did not observe a measurable effect of Na+ on the oxidase activity of purified vbo3 solubilized in detergent or reconstituted in liposomes. (ii) Using fluorescent dyes, we find that vbo3 does not pump Na+ ions, but H+ across the membrane, and that H+-pumping is not influenced by the presence of Na+. (iii) Using an oxygen pulse method, it was found that 2 H+/e- are ejected from proteoliposomes, in agreement with the values found for the H+-pumping bo3 oxidase of Escherichia coli (ecbo3). This coincides with the interpretation that 1 H+/e- is pumped across the membrane and 1 H+/e- is released during quinol oxidation. (iv) When the electron transfer kinetics of vbo3 upon reaction with oxygen were followed in single turnover experiments, a similar sequence of reaction steps was observed as reported for the E. coli enzyme and none of these reactions was notably affected by the presence of Na+. Overall the data show that vbo3 is a proton pumping terminal oxidase, behaving similarly to the Escherichia coli bo3 quinol oxidase.

Construction and application of a Xanthomonas campestris CGMCC15155 strain that produces white xanthan gum.

In the industrial production of xanthan gum using Xanthomonas campestris CGMCC15155, large amounts of ethanol are required to extract xanthan gum from the fermentation broth and remove xanthomonadin impurities. To reduce the amount of ethanol and the overall production cost of xanthan gum, a xanthomonadin-deficient strain of CGMCC15155 was constructed by inserting the Vitreoscilla globin (vgb) gene, under the control of the LacZ promoter, into the region of the pigA gene, which is involved in xanthomonadin synthesis. The insertion of vgb inactivated pigA, resulting in the production of white xanthan gum. The lack of xanthomonadins resulted in a decreased yield of xanthan gum. However, the expression product of vgb gene, VHb, could increase the metabolism of X. campestris, which allowed the production of xanthan gum to reach wild-type levels in the engineered strain. The yield, molecular weight, and rheological properties of the xanthan gum synthesized by the engineered and wild-type bacteria were essentially the same. When the same volume of ethanol was used, the whiteness values of the xanthan gum extracted from engineered and wild-type bacteria were 65.20 and 38.17, respectively. To extract xanthan gum with the same whiteness, three and seven times the fermentation volume of ethanol was required for the engineered and wild-type strains, respectively. Thus, the engineered train reduced the requirement for ethanol in xanthan gum production by 133.3%. The results demonstrated that the engineered bacteria used less ethanol, thus reducing the downstream processing cost in xanthan gum production.

Anaerobic production of medium-chain fatty alcohols via a ß-reduction pathway.

In this report, we identify the relevant factors to increase production of medium chain n-alcohols through an expanded view of the reverse ß-oxidation pathway. We began by creating a base strain capable of producing medium chain n-alcohols from glucose using a redox-balanced and growth-coupled metabolic engineering strategy. By dividing the heterologous enzymes in the pathway into different modules, we were able to identify and evaluate homologs of each enzyme within the pathway and identify several capable of enhancing medium chain alcohol titers and/or selectivity. In general, the identity of the trans-2-enoyl-CoA reductase (TER) and the direct overexpression of the thiolase (FadA) and ß-hydroxy-acyl-CoA reductase (FadB) improved alcohol titer and the identity of the FadBA complex influenced the dominant chain length. Next, we linked the anaerobically induced VHb promoter from Vitreoscilla hemoglobin to each gene to remove the need for chemical inducers and ensure robust expression. The highest performing strain with the autoinduced reverse ß-oxidation pathway produced n-alcohols at titers of 1.8 g/L with an apparent molar yield of 0.2 on glucose consumed in rich medium (52% of theoretical yield).

Increasing oxygen availability for improving poly(3-hydroxybutyrate) production by Halomonas.

Technologies enabling high-cell-density growth are required for economical industrial production of most biotechnological products. However, the key factor limiting cell density in bioreactors is the availability of oxygen during the late phases of fermentation. Although the expression of bacterial Vitreoscilla hemoglobin (VHb) is useful for enhanced oxygen availability, bacterial cell membrane makes efficient hemoglobin-oxygen contact a challenge. On the other hand, periplasmic spaces of Gram-negative microorganisms offer an excellent compartment for the intermittent storage of hemoglobin-bound oxygen. In this study, the cell growth was increased by a remarkable 100% using the twin-arginine translocase (Tat) pathway to export active VHb into the periplasm of Escherichia coli, Halomonas bluephagenesis TD01 and H. campaniensis LS21. Furthermore, eight low-oxygen-inducible vgb promoters were constructed in tandem to become a strong promoter cassette termed P8vgb, which better induces expression of both gene vgb encoding VHb and the PHB synthesis operon microaerobically. Both the P8vgb and VHb performed excellently in E. coli and two Halomonas spp., demonstrating their universal applicability for various organisms.

Enhanced bacterial cellulose production by Gluconacetobacter xylinus via expression of Vitreoscilla hemoglobin and oxygen tension regulation.

Oxygen plays a key role during bacterial cellulose (BC) biosynthesis by Gluconacetobacter xylinus. In this study, the Vitreoscilla hemoglobin (VHb)-encoding gene vgb, which has been widely applied to improve cell survival during hypoxia, was heterologously expressed in G. xylinus via the pBla-VHb-122 plasmid. G. xylinus and G. xylinus-vgb + were statically cultured under hypoxic (10 and 15% oxygen tension in the gaseous phase), atmospheric (21%), and oxygen-enriched conditions (40 and 80%) to investigate the effect of oxygen on cell growth and BC production. Irrespective of vgb expression, we found that cell density increased with oxygen tension (10-80%) during the exponential growth phase but plateaued to the same value in the stationary phase. In contrast, BC production was found to significantly increase at lower oxygen tensions. In addition, we found that BC production at oxygen tensions of 10 and 15% was 26.5 and 58.6% higher, respectively, in G. xylinus-vgb + than that in G. xylinus. The maximum BC yield and glucose conversion rate, of 4.3 g/L and 184.7 mg/g, respectively, were observed in G. xylinus-vgb + at an oxygen tension of 15%. Finally, BC characterization suggested that hypoxic conditions enhance BC's mass density, Young's modulus, and thermostability, with G. xylinus-vgb + synthesizing softer BC than G. xylinus under hypoxia as a result of a decreased Young's modulus. These results will facilitate the use of static culture for the production of BC.

Synergic regulation of redox potential and oxygen uptake to enhance production of coenzyme Q10 in Rhodobacter sphaeroides.

The physiological role of Coenzyme Q10 (CoQ10) as an electron carrier suggests its association with redox potential. Overexpression of glyceraldehyde-3-phosphate dehydrogenase type I (gapA-1) in Rhodobacter sphaeroides elevated the NADH/NAD+ ratio and meanwhile enhanced the CoQ10 content by 58%, but at the sacrifice of biomass. On the other hand, Vitreoscilla hemoglobin was heterologously expressed to enhance the oxygen uptake ability of the cells, leading to 127% improvement of biomass. Subsequent coexpression of gapA-1 and vgb resulted in a CoQ10 titer of 83.24mg/L, representing 71% improvement as compared to the control strain RspMCS. When gapA-1 and vgb genes were co-expressed in a previously created strain RspMQd [1], 163.5mg/L of CoQ10 was produced. Finally, 600mg/L of CoQ10 production was achieved in fed-batch fermentation. These results demonstrated the synergic effect of redox potential regulation and oxygen uptake improvement on enhancing CoQ10 production in R. sphaeroides.

Structural and biological characteristics of different forms of V. filiformis lipid A: use of MS to highlight structural discrepancies.

Vitreoscilla filiformis is a Gram-negative bacterium isolated from spa waters and described for its beneficial effects on the skin. We characterized the detailed structure of its lipopolysaccharide (LPS) lipid A moiety, an active component of the bacterium that contributes to the observed skin activation properties. Two different batches differing in postculture cell recovery were tested. Chemical analyses and mass spectra, obtained before and after mild-alkali treatments, revealed that these lipids A share the common bisphosphorylated ß-(1→6)-linked d-glucosamine disaccharide with hydroxydecanoic acid in an amide linkage. Short-chain FAs, hydroxydecanoic and dodecanoic acid, were found in a 2:1 ratio. The two lipid A structures differed by the relative amount of the hexa-acyl molecular species and phosphoethanolamine substitution of the phosphate groups. The two V. filiformis LPS batches induced variable interleukin-6 and TNF-α secretion by stimulated myelomonocytic THP-1 cells, without any difference in reactive oxygen species production or activation of caspase 3/7. Other different well-known highly purified LPS samples were characterized structurally and used as standards. The structural data obtained in this work explain the low inflammatory response observed for V. filiformis LPS and the previously demonstrated beneficial effects on the skin.

Aerobic expression of Vitreoscilla hemoglobin improves the growth performance of CHO-K1 cells.

Inefficient carbon metabolism is a relevant issue during the culture of mammalian cells for the production of biopharmaceuticals. Therefore, cell engineering strategies to improve the metabolic and growth performance of cell lines are needed. The expression of Vitreoscilla stercoraria hemoglobin (VHb) has been shown to significantly reduce overflow metabolism and improve the aerobic growth of bacteria. However, the effects of VHb on mammalian cells have been rarely studied. Here, the impact of VHb on growth and lactate accumulation during CHO-K1 cell culture was investigated. For this purpose, CHO-K1 cells were transfected with plasmids carrying the vgb or gfp gene to express VHb or green fluorescence protein (GFP), respectively. VHb expression increased the specific growth rate and biomass yields on glucose and glutamine by 60 %, and reduced the amount of lactate produced per cell by 40 %, compared to the GFP-expression controls. Immunofluorescence microscopy showed that VHb is distributed in the cytoplasm and organelles, which support the hypothesis that VHb could serve as an oxygen carrier, enhancing aerobic respiration. These results are useful for the development of better producing cell lines for industrial applications.

Improved production of trans-4-hydroxy-l-proline by chromosomal integration of the Vitreoscilla hemoglobin gene into recombinant Escherichia coli with expression of proline-4-hydroxylase.

trans-4-Hydroxy-l-proline (Hyp) is a chiral amino acid conventionally produced by acid hydrolysis of animal collagen, a process which involves the bottleneck problems of low efficiency and heavy environmental pollution. Biotransformation of l-proline into Hyp using recombinant whole-cell biocatalysis with proline-4-hydroxylase (P4H) is an environmentally-friendly alternative method. Since biohydroxylation of proline by whole cells is a high-oxygen-demand process, oxygen transfer needs to be improved. To solve this problem, the Vitreoscilla hemoglobin gene (vgb) was integrated into the chromosome of recombinant Escherichia coli expressing the P4H gene originally from Dactylosporangium sp. RH1. Expression of Vitreoscilla hemoglobin (VHb) resulted in a 94.4% increase of Hyp production in a 100-mL shaking flask culture compared to the same strain without VHb expression. Meanwhile in a fed-batch fermentation with a 1.4 L bioreactor, the expression of VHb led to an increase in Hyp production by 73.2% and biomass improved by 106%. We also found that acetic acid concentration was decreased by the expression of VHb during the fermentation. This work demonstrates that vgb chromosomal integration is an efficient way to improve Hyp production by enhancing oxygen transfer in recombinant E. coli.

Characterization of Endogenous and Reduced Promoters for Oxygen-Limited Processes Using Escherichia coli.

Oxygen limitation can be used as a simple environmental inducer for the expression of target genes. However, there is scarce information on the characteristics of microaerobic promoters potentially useful for cell engineering and synthetic biology applications. Here, we characterized the Vitreoscilla hemoglobin promoter (Pvgb) and a set of microaerobic endogenous promoters in Escherichia coli. Oxygen-limited cultures at different maximum oxygen transfer rates were carried out. The FMN-binding fluorescent protein (FbFP), which is a nonoxygen dependent marker protein, was used as a reporter. Fluorescence and fluorescence emission rates under oxygen-limited conditions were the highest when FbFP was under transcriptional control of PadhE, Ppfl and Pvgb. The lengths of the E. coli endogenous promoters were shortened by 60%, maintaining their key regulatory elements. This resulted in improved promoter activity in most cases, particularly for PadhE, Ppfl and PnarK. Selected promoters were also evaluated using an engineered E. coli strain expressing Vitreoscilla hemoglobin (VHb). The presence of the VHb resulted in a better repression using these promoters under aerobic conditions, and increased the specific growth and fluorescence emission rates under oxygen-limited conditions. These results are useful for the selection of promoters for specific applications and for the design of modified artificial promoters.