Purification of lactulose from mixtures with lactose using pressurized liquid extraction with ethanol-water at different temperatures

Production of high-purity lactulose via an integrated one-pot boronate affinity adsorbent based adsorption-assisted isomerization and simultaneous purification

High-purity lactulose is mandatory for its medical uses and food applications. This work developed an efficient lab-scale strategy for the synthesis of high-purity lactulose by combining lactose-to-lactulose isomerization with simultaneous recovery of lactulose, which was conducted concurrently and semi-continuously in a boronate affinity adsorbent-packed column. The first step covers the boronate affinity adsorbent-based adsorption-assisted lactose-to-lactulose isomerization. Under optimized conditions, in situ selectively binding of the newly formed lactulose onto the boronate affinity adsorbent enables a much-enhanced lactulose yield up to 80.20% with the lowest byproducts yield of 6.30%. Afterward, over 90% of the adsorbed lactulose can be recovered through sequential desorption with purity >98%. The net outcome of the applied strategy was the yield of high-purity lactulose up to 72.31%, the highest value ever reported. Moreover, the packed column displayed excellent operational stability. The encouraging results validate the high potential of this approach in the sustainable production of high-purity lactulose.

Lactulose production from lactose isomerization by chemo-catalysts and enzymes: Current status and future perspectives

Lactulose, a semisynthetic nondigestive disaccharide with versatile applications in the food and pharmaceutical industries, has received increasing interest due to its significant health-promoting effects. Currently, industrial lactulose production is exclusively carried out by chemical isomerization of lactose via the Lobry de Bruyn-Alberda van Ekenstein (LA) rearrangement, and much work has been directed toward improving the conversion efficiency in terms of lactulose yield and purity by using new chemo-catalysts and integrated catalytic-purification systems. Lactulose can also be produced by an enzymatic route offering a potentially greener alternative to chemo-catalysis with fewer side products. Compared to the controlled trans-galactosylation by β-galactosidase, directed isomerization of lactose with high isomerization efficiency catalyzed by the most efficient lactulose-producing enzyme, cellobiose 2-epimerase (CE), has gained much attention in recent decades. To further facilitate the industrial translation of CE-based lactulose biotransformation, numerous studies have been reported on improving biocatalytic performance through enzyme mediated molecular modification. This review summarizes recent developments in the chemical and enzymatic production of lactulose. Related catalytic mechanisms are also highlighted and described in detail. Emerging techniques that aimed at advancing lactulose production, such as the boronate affinity-based technique and molecular biological techniques, are reviewed. Finally, perspectives on challenges and opportunities in lactulose production and purification are also discussed.

Phenylboronic Acid Functionalized Adsorbents for Selective and Reversible Adsorption of Lactulose from Syrup Mixtures

Boronate affinity materials have been widely used for enrichment of cis-diol molecules. In this work, phenylboronic acid functionalized adsorbents were prepared via a simple and efficient procedure grafting phenylboronic acid groups onto amino macroporous resins. Elemental analysis has confirmed the successful functionalization of AR-1M and AR-2M with approximately 2.17% and 0.73% weight percentage of boron. Comparatively, AR-1M possessed higher lactulose adsorption capacity ( q_e-Lu, 84.78 ± 0.95 mg/g dry resin) under neutral conditions (pH = 7), while the introduced glutaraldehyde spacer arms on AR-2M resulted in excellent adsorption selectivity (α ≈ 23), high adsorption efficiency (π ≈ 22%), and fast adsorption/desorption rate. The purity of lactulose (Pu_D^Lu) through pH-driven adsorption (pH 7-8) and desorption (pH 1.5) can be effectively improved depending on the ratio of lactulose to lactose. When lactulose/lactose ≥ 1:1, Pu_D^Lu ≈ 95% was achieved. No significant drop in q_e-Lu (>90%) was observed after ten-consecutive repeats. Results demonstrated that the newly developed method may achieve satisfactory performance in lactulose purification.

Pressurized liquid extraction of Aglaonema sp. iminosugars: Chemical composition, bioactivity, cell viability and thermal stability

Pressurized liquid extraction of Aglaonema sp. iminosugars has been optimized. A single cycle under optimal conditions (80mg, 100°C, 2min) was enough to extract ⩾96% of most iminosugars. Further incubation with Saccharomyces cerevisiae for 5h removed coextracted interfering low molecular weight carbohydrates from extracts of different Aglaonema cultivars. A complete characterization of these extracts was carried out by gas chromatography-mass spectrometry: three iminosugars were tentatively identified for the first time; α-homonojirimycin and 2,5-dideoxy-2,5-imino-d-mannitol were the major iminosugars determined. α-Glucosidase inhibition activity, cell viability and thermal stability of Aglaonema extracts were also evaluated. Extracts with IC50 for α-glucosidase activity in the 0.010-0.079mgmL(-1) range showed no decrease of Caco-2 cell viability at concentrations lower than 125μgmL(-1) and were stable at 50°C for 30days. These results highlight the potential of Aglaonema extracts as a source of bioactives to be used as functional ingredients.

New methodologies for the extraction and fractionation of bioactive carbohydrates from mulberry (Morus alba) leaves

Pressurized liquid extraction (PLE) was applied for the first time to extract bioactive low molecular weight carbohydrates (iminosugars and inositols) from mulberry ( Morus alba ) leaves. Under optimized conditions, PLE provided a similar yield to the conventional process used to extract these bioactives, but in less time (5 vs 90 min). To remove carbohydrates that interfere with the bioactivity of iminosugars from PLE extracts, two fractionation treatments were evaluated: yeast ( Saccharomyces cerevisiae ) incubation and cation-exchange chromatography (CEC). Both methods allowed complete removal of major soluble carbohydrates (fructose, glucose, galactose, and sucrose), without affecting the content of mulberry bioactives. As an advantage over CEC, the yeast treatment preserves bioactive inositols, and it is an affordable methodology that employs food grade solvents. This work found PLE followed by yeast treatment to be an easily scalable and automatable procedure that can be implemented in the food industry.

Lactulose: production, purification and potential applications

Lactulose a "bifidus factor" is composed of galactose and fructose, which can be produced by the isomerization of lactose. It is a prebiotic carbohydrate which stimulates the growth of health-promoting bacteria in the gastrointestinal tract, such as bifidobacteria and lactobacilli and at the same time inhibits growth of pathogenic bacteria such as Salmonella. It can also be used for the treatment of constipation, hepatic encephalopathy, tumour prevention, and to maintain blood glucose and insulin level. This review provides comprehensive information on the different techniques used for the production of lactulose, purification and analysis. Besides this mechanism of action and its potential applications in food and pharmaceutical industries have also been discussed.

Optimization of extracting stachyose from Stachys floridana Schuttl. ex Benth by response surface methodology

Stachys floridana schuttl. E x benth, also named yinmiao, is a special and traditional Chinese vegetable that is usually used by some diabetes patients as a pharmaceutical plant for its high content of stachyose. Due to the lower cost and higher economic reward, Stachys floridana schuttl. Ex benth is a potentially new source to extract stachyose in the medicine and food industry. Here we optimized the extraction of stachyose from Stachys floridana schuttl. Ex benth by response surface methodology, the yeild can reach as high as up to 47.0% of stachyose at temperature of 60 °C, extraction time of 40 min, ethanol volume of 60% and ratio of solid-liquid at 1:10. Our primary result holds great promising for Stachys floridana schuttl. Ex bent extracting industry as well as diabetic medicine.

Fractionation of honey carbohydrates using pressurized liquid extraction with activated charcoal

This article describes the development of a new procedure that combines the use of activated charcoal and pressurized liquid extraction (PLE) to obtain enriched fractions of di- and trisaccharides from honey. Honey was adsorbed onto activated charcoal and packed into a PLE extraction cell. Optimum results were obtained at 10 MPa and 40 degrees C using two consecutive PLE cycles: first, 1:99 (v/v) ethanol/water for 5 min and second, 50:50 (v/v) ethanol/water for 10 min. Di- and trisaccharide fractions were enriched after PLE treatment, accounting for 73% and 8% of total carbohydrates, respectively. This procedure was also compared with other methodologies reported in the literature for the fractionation of honey carbohydrates (yeast treatment and extraction from activated charcoal). While the removal of monosaccharides was more efficient with yeast treatment, recovery of di- and trisaccharides was higher when either the PLE or the activated charcoal treatment was used. PLE was found to be the faster technique; it also required less solvent volume and minimized handling of the sample.