Development of a recombinant d-mannose isomerase and its characterizations for d-mannose synthesis

Characterization of Runella zeae D-mannose 2-epimerase and its expression in Bacillus subtilis for D-mannose production from D-glucose

D-Mannose 2-epimerase (MEase) catalyzes the bioconversion between D-glucose and D-mannose. It is an important potential biocatalyst for large-scale production of D-mannose, a functional monosaccharide used in pharmaceutical and food industries. In this study, a new microbial MEase was characterized from Runella zeae DSM 19591. The enzyme was purified by one-step nickel-affinity chromatography and determined to be a dimeric protein with two identical subunits of approximately 86.1 kDa by gel filtration. The enzyme showed the highest activity at pH 8.0 and 40 °C, with a specific activity of 2.99 U/mg on D-glucose and 3.71 U/mg on D-mannose. The melting temperature (Tm) was 49.4 °C and the half-life was 115.14 and 3.23 h at 35 and 40 °C, respectively. The purified enzyme (1 U/mL) produced 115.7 g/L of D-mannose from 500 g/L of D-glucose for 48 h, with a conversion ratio of 23.14 %. It was successfully expressed in Bacillus subtilis WB600 via pP43NMK as the vector. The highest fermentation activity was 10.58 U/mL after fed-batch cultivation for 28 h, and the whole cells of recombinant B. subtilis produced 114.0 g/L of D-mannose from 500 g/L of D-glucose, with a conversion ratio of 22.8 %.

Characterization of a novel recombinant D-mannose isomerase from Bifidobacterium bifidum and its catalytic mechanism

Due to the increasing demand for health-conscious and environmentally friendly products, D-mannose has gained significant attention as a natural, low-calorie sweetener. The use of D-mannose isomerases (D-MIases) for D-mannose production has emerged as a prominent area of research, offering superior advantages compared with conventional methods such as plant extraction and chemical synthesis. In this study, a gene encoding D-MIase was cloned from Bifidobacterium and expressed in E. coli BL21 (DE3). The heterologously expressed enzyme, Bifi-mannose, formed a trimer with a molecular weight of 146.3 kDa and a melting temperature (Tm) of 63.39 ± 1.3 °C. Bifi-mannose exhibited optimal catalytic activity at pH 7.5 and 55 °C, and retained more than 80% of its activity after a 3-hour incubation at 55 °C, demonstrating excellent thermal stability. The Km, Vmax, and kcat/Km values of Bifi-mannose for D-fructose isomerization were determined as 538.7 ± 62.5 mM, 11.7 ± 0.9 μmol·mg1·s1, and 1.02 ± 0.3 mM1·s1, respectively. Notably, under optimized conditions, catalytic yields of 29.4, 87.1, and 148.5 mg·mL1 were achieved when using 100, 300, and 500 mg·mL1 of D-fructose as substrates, resulting in a high conversion rate (29%). Furthermore, kinetic parameters and molecular docking studies revealed that His387 residue primarily participates in the opening of the pyranose ring, while His253 acts as a basic catalyst in the isomerization process.

One-Pot Three-Enzyme System for Production of a Novel Prebiotic Mannosyl-β-(1 → 4)-Fructose Using a d-Mannose Isomerase from Xanthomonas phaseoli

The present supply of prebiotics is entirely inadequate to meet their demand. To produce novel prebiotics, a d-mannose isomerase (XpMIaseA) from Xanthomonas phaseoli was first produced in Komagataella phaffii (Pichia pastoris). XpMIaseA shared the highest amino acid sequence identity (58.0%) with the enzyme from Marinomonas mediterranea. Efficient secretory production of XpMIaseA (282.0 U mL^-1) was achieved using high cell density fermentation. The optimal conditions of XpMIaseA were pH 7.5 and 55 °C. It showed a broad substrate specificity, which isomerized d-mannose, d-talose, mannobiose, epilactose, and mannotriose. XpMIaseA was employed to construct a one-pot three-enzyme system for the production of mannosyl-β-(1 → 4)-fructose (MF) using mannan (5%, w/v) as the substrate. The equilibrium yield of MF was 58.2%. In in vitro fermentations, MF significantly stimulated (≤3.2-fold) the growth of 12 among 15 tested Bifidobacterium and Lactobacillus strains compared with fructo-oligosaccharides. Thus, the novel d-mannose isomerase provides a one-pot bioconversion strategy for efficiently producing novel prebiotics.

Recent advances in biotransformation, extraction and green production of D-mannose

D-mannose is a natural and biologically active monosaccharide. It is the C-2 epimer of glucose and a component of a variety of polysaccharides in plants. In addition, D-mannose also naturally exists in some cells of the human body and participates in the immune regulation of cells as a prebiotic. Its good physiological benefits to human health and wide application in the food and pharmaceutical industries have attracted widespread attention. Therefore, in-depth research on preparation methods of D-mannose has been widely developed. This article summarizes the main production methods of D-mannose in recent years, especially the in-depth excavation from biomass raw materials such as coffee grounds, konjac flour, acai berry, etc., to provide new ideas for the green manufacture of D-mannose.

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Various methods of recent mannose production were comprehensively summarized.

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The new technical progress of obtaining mannose from biomass as emphatically discussed.

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Discuss various preparation methods including different pretreatments, enzymatic hydrolysis, etc.

Biochemical Properties of a Novel D-Mannose Isomerase from Pseudomonas syringae for D-Mannose Production

D-Mannose isomerase can reversibly catalyze D-fructose to D-mannose which has various beneficial effects. A novel D-mannose isomerase gene (PsMIaseA) from Pseudomonas syringae was cloned and expressed in Escherichia coli. The recombinant D-mannose isomerase (PsMIaseA) showed the highest amino acid sequence homogeneity of 50% with ManI from Thermobifda fusca. PsMIaseA was purified through Ni-NTA chromatography, and its specific activity was 818.6 U mg^-1. The optimal pH and temperature of PsMIaseA were pH 7.5 and 45 °C, respectively. The enzyme was stable within a wide pH range from 5.0 to 10.0. It could efficiently convert D-fructose to D-mannose without any metal ions. When PsMIaseA was incubated with 600 g/L D-fructose for 6 h, the space-time yield of D-mannose reached 27.2 g L^-1 h^-1 with a maximum conversion ratio of 27%. Therefore, the D-mannose isomerase may be suitable for green production of D-mannose.

Efficient production of extracellular pullulanase in Bacillus subtilis ATCC6051 using the host strain construction and promoter optimization expression system

Background

Bacillus subtilis has been widely used as a host for heterologous protein expression in food industry. B. subtilis ATCC6051 is an alternative expression host for the production of industrial enzymes, and exhibits favorable growth properties compared to B. subtilis 168. Extracellular expression of pullulanase from recombinant B. subtilis is still limited due to the issues on promoters of B. subtilis expression system. This study was undertaken to develop a new, high-level expression system in B. subtilis ATCC6051.

Results

To further optimize B. subtilis ATCC6051 as a expression host, eight extracellular proteases (aprE, nprE, nprB, epr, mpr, bpr, vpr and wprA), the sigma factor F (spoIIAC) and a surfactin (srfAC) were deleted, yielding the mutant B. subtilis ATCC6051∆10. ATCC6051∆10 showed rapid growth and produced much more extracellular protein compared to the widetype strain ATCC6051, due to the inactivation of multiple proteases. Using this mutant as the host, eleven plasmids equipped with single promoters were constructed for recombinant expression of pullulanase (PUL) from Bacillus naganoensis. The plasmid containing the P_spovG promoter produced the highest extracellular PUL activity, which achieved 412.9 U/mL. Subsequently, sixteen dual-promoter plasmids were constructed and evaluated using this same method. The plasmid containing the dual promoter P_amyL–P_spovG produced the maximum extracellular PUL activity (625.5 U/mL) and showed the highest expression level (the dry cell weight of 18.7 g/L).

Conclusions

Taken together, we constructed an effective B. subtilis expression system by deleting multiple proteases and screening strong promoters. The dual-promoter P_amyL–P_spovG system was found to support superior expression of extracellular proteins in B. subtilis ATCC6051.

Electronic supplementary material

The online version of this article (10.1186/s12934-018-1011-y) contains supplementary material, which is available to authorized users.

Production of d-mannose from d-glucose by co-expression of d-glucose isomerase and d-lyxose isomerase in Escherichia coli

BACKGROUND

d-Mannose is not only the epimer of d-glucose at the C-2 position, but also the aldose isomer of d-fructose. Because of its physiological properties and health benefits, d-mannose has attracted public interest. It has been confirmed that d-mannose has broad applications in food, cosmetics, and pharmaceutical industries. According to the Izumoring strategy, d-glucose isomerase (d-GI) and d-lyxose isomerase (d-LI) play important roles in the conversions of d-fructose from d-glucose and of d-mannose from d-fructose respectively. In this study, a one-step enzyme process of d-mannose production from d-glucose has been constructed by co-expression of the d-GI from Acidothermus cellulolyticus and d-LI from Thermosediminibacter oceani in Escherichia coli BL21(DE3) cells.

RESULTS

The co-expression system exhibits maximum activity at pH 6.5 and 65 °C with Co²⁺ supplement. It is relatively thermostable at less than 65 °C. When the reaction reaches equilibrium, the ratio of d-glucose, d-fructose, and d-mannose is approximately 34 : 49.6 : 16.4. By using this co-expression system, about 60.0 g L^-1 d-mannose is obtained from 400 g L^-1 d-glucose in 8 h.

CONCLUSION

This co-expression of d-GI and d-LI system provides a novel and efficient approach for d-mannose production. © 2018 Society of Chemical Industry.