Production Methods ofD-Mannitol

New Insights Into the Biosynthesis of Typical Bioactive Components in the Traditional Chinese Medicinal Fungus Cordyceps militaris

Cordyceps militaris, a traditional medicinal ingredient with a long history of application in China, is regarded as a high-value fungus due to its production of various bioactive ingredients with a wide range of pharmacological effects in clinical treatment. Several typical bioactive ingredients, such as cordycepin, D-mannitol, cordyceps polysaccharides, and N⁶-(2-hydroxyethyl)-adenosine (HEA), have received increasing attention due to their antitumor, antioxidant, antidiabetic, radioprotective, antiviral and immunomodulatory activities. Here, we systematically sorted out the latest research progress on the chemical characteristics, biosynthetic gene clusters and pathways of these four typical bioactive ingredients. This summary will lay a foundation for obtaining low-cost and high-quality bioactive ingredients in large amounts using microbial cell factories in the future.

An ATP-free in vitro synthetic enzymatic biosystem facilitating one-pot stoichiometric conversion of starch to mannitol

D-Mannitol (hereinafter as mannitol) is a six-carbon sugar alcohol with diverse applications in food and pharmaceutical industries. To overcome the drawbacks of the chemical hydrogenation method commonly used for mannitol production at present, there is a need to search for novel prospective mannitol production strategies that are of high yield and low cost. In this study, we present a novel approach for the stoichiometric synthesis of mannitol via an in vitro synthetic enzymatic biosystem using the low-cost starch as substrate. By dividing the overall reaction pathway into three modules which could be executed sequentially in one pot, our design aimed at the stoichiometric conversion of starch-based materials into mannitol in an ATP-independent and cofactor-balanced manner. At optimized conditions, high product yields of around 95-98% were achieved using both 10 g/L and 50 g/L maltodextrin as substrate, indicating the potential of our designed system for industrial applications. This study not only provides a high-efficient strategy for the synthesis of mannitol but also expands the product scope of sugar alcohols by the in vitro synthetic enzymatic biosystems using low-cost starch-based materials as the input. KEY POINTS : • We described a design-build-test-learn pipeline to construct in vitro biosystems. • The designed system comprised six key enzymes and another three enzymes. • The system converted maltodextrin stoichiometrically to mannitol in one pot.

Selective and Scalable Synthesis of Sugar Alcohols by Homogeneous Asymmetric Hydrogenation of Unprotected Ketoses

Sugar alcohols are of great importance for the food industry and are promising building blocks for bio-based polymers. Industrially, they are produced by heterogeneous hydrogenation of sugars with H₂ , usually with none to low stereoselectivities. Now, we present a homogeneous system based on commercially available components, which not only increases the overall yield, but also allows a wide range of unprotected ketoses to be diastereoselectively hydrogenated. Furthermore, the system is reliable on a multi-gram scale allowing sugar alcohols to be isolated in large quantities at high atom economy.

Technical Parameters Affecting the Spray Drying of Roselle (Hibiscus Sabdariffa) Powder

Roselle (Hibiscus sabdariffa) was a member of Malvaceae family. Its calyxes had bright red color due to presence of anthocyanin with an excellent antioxidant property. Raw roselle (Hibiscus sabdariffa L.) calyx was highly perishable due to its high moisture content. In order to diversify products from this plant, this research evaluated the possibility of spray drying for roselle extract into dried powder for long-term consumption. We focused on the effect of sugar alcohols (mannitol, sorbitol, isomalt, xylitol, erythritol) at 8%, carrier agents (maltodextrin, gum arabic, glutinous starch, whey protein concentrate, carboxymethyl cellulose) at 12%, operating parameters of spray dryer (inlet/outlet air temperature, feed rate) on physicochemical quality (bulk density, solubility, total phenolic content, total flavonoid content, anthocyanin content) of rosselle powder. Results showed that the optimal spray drying variables for rosselle powder should be 8% isomalt, 12% whey protein concentrate, inlet/ outlet air temperature 140/85oC/oC, feed rate 12 ml/min. Based on these optimal conditions, the highest physicochemical attributes of the dried roselle calyx powder would be obtained.

Study of olive pomace antioxidant dietary fibre powder throughout gastrointestinal tract as multisource of phenolics, fatty acids and dietary fibre

Pulp-enriched powder (POPP) was obtained from olive pomace solid fraction, a derived from the new value chain established for olive by-products. As a multifunctional powder, POPP retains several bioactive compounds (fatty acids, dietary fibre and phenolics) under potential synergic interaction, even more, reactive throughout the digestion. So, in this study, the potential multifunctionality of POPP was evaluated after the gastrointestinal tract. A significant loss of phenolics occurred during oral digestion (62.48%). However, the potential role of dietary fibre as phenolics' carrier and its possible liberation in the stomach allowed recovering a significant amount of phenolics (77.11%) and a bioaccessibility index of at least 50% (mainly for tyrosol and its glucoside). POPP also provides high content of dietary fibre mainly insoluble fibre (69.68 g/100 g dry weight) linked to a substantial amount of bound phenolics (7.63 mg of gallic acid equivalents/g fibre dry weight), with a positive effect on the fatty acids bioaccessibility [decreased the saturated (5-6%) and facilitated the unsaturated fatty acids bioaccessibility (4-11%)]. PCA analysis became evident the negative effect of simulated gastrointestinal digestion upon POPP as mainly linked to phenolics' loss. Despite all negative effects of the simulated digestion on POPP bioactive composition, phenolics and unsaturated fatty acids showed to be bioaccessible in significant amount, and the amount of bound phenolics associated to fibre retained in the colon have the potential to exert gut health benefits.

A Robust and Highly Selective Catalytic System of Copper-Silica Nanocomposite and 1-Butanol in Fructose Hydrogenation to Mannitol

We report for the first time the selective production of mannitol, a low-calorie sweetener and an important pharmaceutical ingredient, from fructose using Cu-SiO₂ nanocomposite as catalyst and 1-butanol as solvent. When compared with water and ethanol, a lower fructose solubility was achieved in 1-butanol, which caused a lower fructose conversion and higher mannitol selectivity by reducing formation of side products. Among various Cu-based catalysts in 1-butanol, Cu(80)-SiO₂ nanocomposite gave an unprecedented mannitol (83 %) and sorbitol (15 %) yield at 120 °C, 35 bar H₂ , and 10 h reaction time. More importantly, this catalyst did not show any Cu leaching and its physicochemical properties were maintained after liquid-phase fructose hydrogenation whereas other Cu-based catalysts such as Cu(32)-Cr₂ O and Cu(66)-ZnO did show significant leaching of Cu and Cr. Thus, Cu(80)-SiO₂ nanocomposite and 1-butanol are regarded as a robust and highly efficient catalytic system for the selective hydrogenation of fructose to mannitol. Also, density functional theory calculations supported that in addition to the stable initial structure of adsorbed fructose, the mannitol pathway was more thermodynamically favorable than the sorbitol pathway. Notably, the highly pure mannitol (99 %) could be recovered from the sorbitol-containing 1-butanol solution by simple filtration. Therefore, the present protocol is a novel and effective method to produce pure mannitol from fructose in both an environmental and an industrial context.

Food Industrial Production of Monosaccharides Using Microbial, Enzymatic, and Chemical Methods

Most monosaccharides in nature are hexoses, which have six carbon atoms; the most well-known hexose is d-glucose. Various hexoses with distinct characteristics can be produced from inexpensive polysaccharides for applications in the food industry. Therefore, identification of the health-related functions of hexose will facilitate the consumption of hexoses in food products to improve quality of life. The hexoses available in foods include N-acetyl glucosamine, d-glucosamine, d-fructose, d-mannose, d-galactose, other d-hexoses, and l-hexoses. Here, an updated overview of food industrial production methods for natural hexoses by microbial, enzymatic, and chemical methods is provided.

Catalytic Hydrogenation of Macroalgae-Derived Alginic Acid into Sugar Alcohols

Alginic acid, a major constituent of macroalgae, iss hydrogenated into sugar alcohols over carbon-supported noble metals for the first time. Mannitol and sorbitol are the major products of the catalytic hydrogenation of alginic acid, which consists of two epimeric uronic acids. The main reaction pathway is the consecutive hydrogenations of the aldehyde and carboxyl ends of alginic acid dimers, followed by the cleavage of the C-O-C linkage into monomeric units by hydrolysis. The highest yield of C₆ sugar alcohols is 61 % (sorbitol: 29 %; mannitol: 28 %; galactitol: 4 %). The low sorbitol/mannitol ratio is in contrast to that from cellulose hydrogenation, owing to the composition of alginic acid and isomerization between sugar alcohols under the catalytic system. This new green route to producing sugar alcohols from alginic acid might provide opportunities to diversify biomass resources.

Construction of an efficient Escherichia coli whole-cell biocatalyst for D-mannitol production

Mannitol is a six carbon sugar alcohol that finds applications in the pharmaceutical and food industries. A novel Escherichia coli strain capable of converting D-glucose to D-mannitol has been constructed, wherein native mannitol-1-phosphate dehydrogenase (MtlD) and codon-optimized Eimeria tenella mannitol-1-phosphatase (M1Pase) have been overexpressed. Codon-optimized Pseudomonas stutzeri phosphite dehydrogenase (PtxD) was overexpressed for cofactor (NADH) regeneration with the concomitant oxidation of phosphite to phosphate. Whole-cell biotransformation using resting cells in a medium containing D-glucose and equimolar sodium phosphite resulted in d-mannitol yield of 87 mol%. Thus, production of an industrially relevant biochemical without using complex media components and elaborate process control mechanisms has been demonstrated.

Biotechnological and in situ food production of polyols by lactic acid bacteria

Polyols such as mannitol, erythritol, sorbitol, and xylitol are naturally found in fruits and vegetables and are produced by certain bacteria, fungi, yeasts, and algae. These sugar alcohols are widely used in food and pharmaceutical industries and in medicine because of their interesting physicochemical properties. In the food industry, polyols are employed as natural sweeteners applicable in light and diabetic food products. In the last decade, biotechnological production of polyols by lactic acid bacteria (LAB) has been investigated as an alternative to their current industrial production. While heterofermentative LAB may naturally produce mannitol and erythritol under certain culture conditions, sorbitol and xylitol have been only synthesized through metabolic engineering processes. This review deals with the spontaneous formation of mannitol and erythritol in fermented foods and their biotechnological production by heterofermentative LAB and briefly presented the metabolic engineering processes applied for polyol formation.

Biotechnological production of mannitol and its applications

Mannitol, a naturally occurring polyol (sugar alcohol), is widely used in the food, pharmaceutical, medical, and chemical industries. The production of mannitol by fermentation has become attractive because of the problems associated with its production chemically. A number of homo- and heterofermentative lactic acid bacteria (LAB), yeasts, and filamentous fungi are known to produce mannitol. In particular, several heterofermentative LAB are excellent producers of mannitol from fructose. These bacteria convert fructose to mannitol with 100% yields from a mixture of glucose and fructose (1:2). Glucose is converted to lactic acid and acetic acid, and fructose is converted to mannitol. The enzyme responsible for conversion of fructose to mannitol is NADPH- or NADH-dependent mannitol dehydrogenase (MDH). Fructose can also be converted to mannitol by using MDH in the presence of the cofactor NADPH or NADH. A two enzyme system can be used for cofactor regeneration with simultaneous conversion of two substrates into two products. Mannitol at 180 g l(-1) can be crystallized out from the fermentation broth by cooling crystallization. This paper reviews progress to date in the production of mannitol by fermentation and using enzyme technology, downstream processing, and applications of mannitol.

Improving d-mannitol productivity of Escherichia coli: impact of NAD, CO2 and expression of a putative sugar permease from Leuconostoc pseudomesenteroides

The highly productive whole-cell biotransformation of D-fructose to D-mannitol with recombinant, resting cells of Escherichia coli BL21(DE3) requires the combined expression of mdh, fdh and glf which encode mannitol and formate dehydrogenases and a sugar facilitator, respectively. However, long-term stability of the system was restricted, possibly due to loss of the cofactor NAD, high concentrations of formate, formation of CO(2) affecting the internal pH of the cells, accumulation of high intracellular concentrations of D-mannitol, and export of D-mannitol. Downstream of the mdh gene of Leuconostoc pseudomesenteroides, we identified an open reading frame encoding for a putative mannitol permease. The gene was cloned and expressed in E. coli. Biochemical analyses revealed an activity as secondary carrier for D-fructose. Therefore, the carrier was named FupL and participation in D-mannitol transport was excluded. In biotransformation experiments, the productivity of D-mannitol formation obtained with the strain expressing the additional fupL gene was enhanced by 20%.

D-mannitol production by resting state whole cell biotrans-formation of D-fructose by heterologous mannitol and formate dehydrogenase gene expression in Bacillus megaterium

An in vivo system was developed for the biotransformation of D-fructose into D-mannitol by the expression of the gene mdh encoding mannitol dehydrogenase (MDH) from Leuconostoc pseudomesenteroides ATCC12291 in Bacillus megaterium. The NADH reduction equivalents necessary for MDH activity were regenerated via the oxidation of formate to carbon dioxide by coexpression of the gene fdh encoding Mycobacterium vaccae N10 formate dehydrogenase (FDH). High-level protein production of MDH in B. megaterium required the adaptation of the corresponding ribosome binding site. The fdh gene was adapted to B. megaterium codon usage via complete chemical gene synthesis. Recombinant B. megaterium produced up to 10.60 g/L D-mannitol at the shaking flask scale. Whole cell biotransformation in a fed-batch bioreactor increased D-mannitol concentration to 22.00 g/L at a specific productivity of 0.32 g D-mannitol (gram cell dry weight)(-1) h(-1) and a D-mannitol yield of 0.91 mol/mol. The nicotinamide adenine dinucleotide (NAD(H)) pool of the B. megaterium producing D-mannitol remained stable during biotransformation. Intra- and extracellular pH adjusted itself to a value of 6.5 and remained constant during the process. Data integration revealed that substrate uptake was the limiting factor of the overall biotransformation. The information obtained identified B. megaterium as a useful production host for D-mannitol using a resting cell biotransformation approach.

Ca2+ and Cu2+ supplementation increases mannitol production by Candida magnoliae

Supplementation with CaCl(2).2H(2)O (50 mg l(-1)) or CuSO(4).5H(2)O (10 mg l(-1)) improved mannitol production by Candida magnoliae by 14.5 and 18.6% (25 and 32 g/L), respectively. When used in combination, they acted synergistically: Ca(2+) decreased the intracellular concentration of mannitol 30%, whereas Cu(2+ )increased the intracellular activity of mannitol dehydrogenase 1.6-times more than control. Ca(2+) probably works by altering the permeability of cells to mannitol, whereas, Cu(2+) increases the activity of an enzyme responsible for mannitol biosynthesis.

Effect of salt nutrients on mannitol production by Lactobacillus intermedius NRRL B-3693

The effects of four salt nutrients (ammonium citrate, sodium phosphate, magnesium sulfate, and manganese sulfate) on the production of mannitol by Lactobacillus intermedius NRRL B-3693 in a simplified medium containing 300 g fructose, 5 g soy peptone, and 50 g corn steep liquor per liter in pH-controlled fermentation at 5.0 at 37 degrees C were evaluated using a fractional factorial design. Only manganese sulfate was found to be essential for mannitol production. Added manganese sulfate concentration of 0.033 g/l was found to support maximum production. The bacterium produced 200.6 +/- 0.2 g mannitol, 61.9 +/- 0.1 g lactic acid, and 40.4 +/- 0.3 g acetic acid from 300 g fructose per liter in 67 h.

A low-cost medium for mannitol production by Lactobacillus intermedius NRRL B-3693

The production of mannitol by Lactobacillus intermedius NNRL B-3693 using molasses as an inexpensive carbon source was evaluated. The bacterium produced mannitol (104 g/l) from molasses and fructose syrups (1:1; total sugars, 150 g/l; fructose:glucose 4:1) in 16 h. Several kinds of inexpensive organic and inorganic nitrogen sources and corn steep liquor were evaluated for their potential to replace more expensive nitrogen sources derived from Bacto-peptone and yeast extract. Soy peptone D (5 g/l) and corn steep liquor (50 g/l) were found to be suitable substitutes for Bacto-peptone (5 g/l) and Bacto-yeast extract (5 g/l), respectively. The bacterium produced 105 g mannitol per liter from the molasses and fructose syrup (1:1, total sugars 150 g/l; fructose:glucose 4:1) in 22 h using a combination of soy peptone D (5 g/l) and corn steep liquor (50 g/l). This is the first report on the production of mannitol by fermentation using molasses and corn steep liquor.

d-Mannitol formation from d-glucose in a whole-cell biotransformation with recombinant Escherichia coli

Recently, we reported on the construction of a whole-cell biotransformation system in Escherichia coli for the production of D: -mannitol from D: -fructose. Supplementation of this strain with extracellular glucose isomerase resulted in the formation of 800 mM D: -mannitol from 1,000 mM D: -glucose. Co-expression of the xylA gene of E. coli in the biotransformation strain resulted in a D: -mannitol concentration of 420 mM from 1,000 mM D: -glucose. This is the first example of conversion of D: -glucose to D: -mannitol with direct coupling of a glucose isomerase to the biotransformation system.

Improved mannitol production by a random mutant of Leuconostoc pseudomesenteroides

A mutant of Leuconostoc pseudomesenteroides ATCC12291 that was unable to grow on fructose was constructed by chemical mutagenesis. The fructose uptake of this mutant, designated as BPT143, was unaltered and allowed fructose still to be converted into mannitol when glucose was present in the growth medium. The mutant grew and consumed fructose faster than the parent strain when grown in a medium containing both glucose and fructose. The specific activity of fructokinase, the enzyme involved in phosphorylation of fructose to fructose-6-phosphate, was decreased to about 10% of that of the parent strain, and resulted in a reduced leakage of fructose into the phosphoketolase (PK) pathway. The yield of mannitol from fructose was improved from 74 to 86 mol%. The increased fructose consumption rate and higher mannitol yield of the mutant also resulted in improvement of volumetric mannitol productivity. In addition, isolation and characterization of the wild type L. pseudomesenteroides fructokinase gene (fruK) was performed. DNA sequence analysis of the fruK gene region of BPT143 revealed only one silent mutation which does not explain the highly reduced fructokinase activity of the mutant. The genetic characterization of fruK was completed by analyzing the expression, size and 5' end of fruK transcripts. Expression data with BPT143, revealing absence of fruK transcripts, was in accordance with the reduced fructokinase activity of the mutant.

Purification and characterization of a novel mannitol dehydrogenase from Lactobacillus intermedius

Mannitol 2-dehydrogenase (MDH) catalyzes the pyridine nucleotide dependent reduction of fructose to mannitol. Lactobacillus intermedius (NRRL B-3693), a heterofermentative lactic acid bacterium (LAB), was found to be an excellent producer of mannitol. The MDH from this bacterium was purified from the cell extract to homogeneity by DEAE Bio-Gel column chromatography, gel filtration on Bio-Gel A-0.5m gel, octyl-Sepharose hydrophobic interaction chromatography, and Bio-Gel Hydroxyapatite HTP column chromatography. The purified enzyme (specific activity, 331 U/mg protein) was a heterotetrameric protein with a native molecular weight (MW) of about 170 000 and subunit MWs of 43 000 and 34 500. The isoelectric point of the enzyme was at pH 4.7. Both subunits had the same N-terminal amino acid sequence. The optimum temperature for the reductive action of the purified MDH was at 35 degrees C with 44% activity at 50 degrees C and only 15% activity at 60 degrees C. The enzyme was optimally active at pH 5.5 with 50% activity at pH 6.5 and only 35% activity at pH 5.0 for reduction of fructose. The optimum pH for the oxidation of mannitol to fructose was 7.0. The purified enzyme was quite stable at pH 4.5-8.0 and temperature up to 35 degrees C. The K(m) and V(max) values of the enzyme for the reduction of fructose to mannitol were 20 mM and 396 micromol/min/mg protein, respectively. It did not have any reductive activity on glucose, xylose, and arabinose. The activity of the enzyme on fructose was 4.27 times greater with NADPH than NADH as cofactor. This is the first highly NADPH-dependent MDH (EC 1.1.1.138) from a LAB. Comparative properties of the enzyme with other microbial MDHs are presented.

Purification and characterisation of mannitol dehydrogenase from Lactobacillus sanfranciscensis

Mannitol dehydrogenase (MDH) was purified and characterised from Lactobacillus sanfranciscensis. Two peptide fragments of MDH were N-terminally sequenced for the first time in the genus Lactobacillus. The purified enzyme had an apparent molecular mass of 44 kDa and catalysed both the reduction of fructose to mannitol and the oxidation of mannitol to fructose. The K(m) value for the reduction reaction was 24 mM fructose and that for the oxidation 78 mM mannitol. The optimum temperature was 35 degrees C, the pH optima for the reduction or oxidation were 5.8 and 8, respectively.

Spontaneous formation of a mannitol-producing variant of Leuconostoc pseudomesenteroides grown in the presence of fructose

We report the spontaneous formation of a stable mannitol-producing variant of Leuconostoc pseudomesenteroides. The mannitol-producing variant showed mannitol dehydrogenase activity which was absent in the parental strain. It was also able to use fructose and glucose simultaneously, whereas the parental strain showed diauxic growth with these sugars. A possible explanation of these observations is discussed.

Hydrogenation of fructose on Ru/C catalysts

The hydrogenation of D-fructose on Ru/C catalysts was studied. Under the conditions applied (1 bar H2, 72 degrees C), the furanose forms of D-fructose react, while the pyranose forms do not. However, all anomers adsorb with comparable strength on the surface. The reaction rate is controlled by product inhibition. The selectivity to D-mannitol can be increased from 47 to 63% by promotion of Pd/C and Pt/C catalysts with Sn.

Cloning and characterization of NADP-mannitol dehydrogenase cDNA from the button mushroom, Agaricus bisporus, and its expression in response to NaCl stress

Mannitol, a six-carbon sugar alcohol, is the main storage carbon in the button mushroom, Agaricus bisporus. Given the physiological importance of mannitol metabolism in growth, fruit body development, and salt tolerance of A. bisporus, the enzyme responsible for mannitol biosynthesis, NADP-dependent mannitol dehydrogenase (MtDH) (EC 1.1.1.138), was purified to homogeneity, and MtDH cDNA was cloned, sequenced, and characterized. To our knowledge, this represents the first report on the isolation of a cDNA encoding an NADP-dependent mannitol dehydrogenase. The MtDH cDNA contains an open reading frame of 789 bp encoding a protein of approximately 28 kDa. The N-terminal and internal amino acid sequences of the deduced protein exactly matched the ones determined from the purified MtDH subunit, whereas the amino acid composition of the deduced protein was nearly identical to that of the purified MtDH. The MtDH cDNA showed high homology with a plant-induced short-chain dehydrogenase from Uromyces fabae. Phylogenetic analysis based on amino acid sequences from mannitol(-1-phosphate) dehydrogenases indicated a close relationship between the substrate specificity of the enzymes and phylogenetic differentiation. Salt-stressed fruit bodies showed an overall increase in mannitol biosynthesis, as was evident from the increase in MtDH activity, MtDH abundance, and MtDH RNA accumulation. Furthermore, the MtDH transcript level seems to be under developmental control, as MtDH RNA accumulated during maturation of the fruit body.