• Journal of Life Science
• /
• v.26 no.12
• /
• pp.1477-1486
• /
• 2016

Lactulose (4-O-${\beta}$-D-galactopyranosyl-D-fructose) is a non-digestible synthetic ketose disaccharide which can used in food and pharmaceutical fields due to its useful functions for encephalopathy, chronic constipation, hyperammonemia, etc. Therefore, the lactulose is regarded as one of the most important disaccharides and have been concentrated much interesting as an attractive functional material in the current industry. From this reason, the research related on the production of lactulose has been carried out various academic and industrial research groups. To produce lactulose, two main methods, chemical production and enzymatic production have been used. Commercially lactulose produced by alkaline isomerization of lactose as chemical production method but it has many disadvantages such as rapid lactulose degradation, purification, and waste management. From these reasons, lactulose produced by enzymatic method which solves these problems has been suggested as a proper method for lactulose production. Two different enzymatic methods have been reported as methods for lactulose production. Lactulose can be obtained through hydrolysis and transfer reaction catalyzed by a ${\beta}$-galactosidase which requires fructose as co-substrate and exhibits a low conversion. Alternatively, lactulose can be produced by direct isomerization of lactose to lactulose catalyzed by cellobiose 2-epimerase which requires lactose as a single substrate and achieves a high lactulose yield. This review summarizes the current state of lactulose production by chemical and biological methods.

• Food Science of Animal Resources
• /
• v.32 no.5
• /
• pp.540-544
• /
• 2012

During heat treatment and storage of milk, deteriorative reaction takes place, which consequently influence on the milk quality. In this study, formation of lactulose and furosine under different thermal conditions and storage conditions, and the ratio of lactulose and furosine (LU/FU) in presence of reconstituted milk powder were determined to establish chemical indicators for heat damages of milk and the adulteration of fresh milk in dairy field. The lactulose and furosine contents linearly increased with increased heating temperature and heating time. It showed high correlation between the formation of lactulose and furosine, and the treatment temperature and time (p<0.05). The lactulose and furosine concentration of HTST milk and UHT milk noticeably increased during storage at $30^{\circ}C$, but there was no noticeable increase of lactulose and furosine concentration at lower storage temperature. In the raw milk, the lactulose and furosine contents greatly increased with the addition of reconstituted milk. The increase level of furosine was much higher than that of lactulose, which consequently resulted in the lower LU/FU ratio in milk as increase of added reconstituted milk amounts. As comparing with raw milk, there was more than twice reduction in LU/FU ratios after the addition of reconstituted milk (p<0.05). It can be concluded that lactulose and furosine are suitable milk quality indicators of heat damage and for demonstrating improper addition of reconstituted milk powder.

• Food Science of Animal Resources
• /
• v.22 no.1
• /
• pp.50-54
• /
• 2002

The aim of this work to determine the formation of lactulose during heat treatment process as a contribution to the estabilishment of limits of chemical indicators for different types of heat processed milk and analyze of lactulose for the reconstituted milk added samples. The HTST(75$\^{C}$/15s) and UHT(130$\^{C}$/2∼3s) treatment realized with a pilot plant and heat-treated samples were stroed at 4, 10, 30$\^{C}$ for 4 weeks. Changes in lactulose was evaluated at 7 days intervals. The other heat treatment was sealed in glass tube and heated at 75$\^{C}$ for 10 to 120s and heated at 130$\^{C}$ for 2 to 60s in a thermostatically controlled constant temperature bath of glycerol. The reconstituted milk was made with full fat dry milk that reconstituted with deionized water to 10% total solid, and was added to milk at 10, 20, 30% respectively. The samples processed with a HTST pilot plant showed that lactulose was contained at 1.47∼1.52mg/10()ml and 8.19 ∼8.32mg/100ml for UHT-treated samples. Changes in the lactulose content of heat-treated samples during storage at 4 and 10$\^{C}$ for 4 weeks caused a slight increase, however a noticeable increase was observed at 30$\^{C}$ for 4 week. The glass tube samples showed that high correlations between relative increase in content of lactulose and increasing processing times(75$\^{C}$ : r = 0.986, 130$\^{C}$ : r = 0.987, respectively). Added with reconstituted milk would cause a increase of the lactulose content linear with increasing addition amount(r = 0.982). This results observed for lactulose in commercial milk samples would applied to the detection of chemical changes during heat treatment and illegal use of reconstituted milk.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.19 no.4
• /
• pp.330-334
• /
• 1990

The lactulose contents in market milks were analyzed by gas chromatographic method. The method is evaluated for accurac and reproducibility using phenyl-$\beta$-D-glucoside as an internal standard. The response factor(RF) of lactulose of standard mixture was 1.15 the recoveries were 97.4-101.3% and the reproducibility was determined on the coefficeitns of variation 24.8% for pasteurized milk and 4.6-4.9% for UHT milk The lactulose contents of 16 brands of the market milks determined were 5.3-59.7mg/100ml in UHT milk and 1.3-1.8mg/100ml in pasteurized milk.

• Asian-Australasian Journal of Animal Sciences
• /
• v.33 no.2
• /
• pp.339-348
• /
• 2020

Objective: This study investigates the technological and sensory profile of boneless dry-cured ham with different contents of lactulose added as a prebiotic ingredient. Methods: In addition to the control samples (without the addition of lactulose), three treatments were formulated to contain 2%, 4%, or 6% lactulose. Technological (lactulose content, instrumental color and texture profile analysis) and sensory (acceptance and check-all-thatapplies tests) analyses were performed on the final product. Results: The lactulose content in the finished product (1.86%±0.23%, 3.16%±0.18%, and 2.51%±1.35%) was lower than the lactulose originally added (2%, 4%, and 6%, respectively). The addition of 4% and 6% lactulose made (p<0.05) the products darker (lower L^⋆) and redder (lower h) with higher hardness and chewiness values, when compared to control samples. The additions of 2% and 4% lactulose reduce the appearance acceptability of the products, but overall the treatments were well accepted. Conclusion: The use of up to 4% lactulose as a prebiotic in the production of boneless dry-cured hams provides an alternative to improving its nutritional value with little alteration in the technological characteristics and still meeting the sensory characteristics desired by consumers.

• Journal of Microbiology and Biotechnology
• /
• v.26 no.7
• /
• pp.1267-1277
• /
• 2016

Currently, enzymatic synthesis of lactulose, a synthetic prebiotic disaccharide, is commonly performed with glycosyl hydrolases. In this work, a new type of lactulose-producing biocatalyst was developed by displaying β-galactosidase from Bacillus stearothermophilus IAM11001 (Bs-β-Gal) on the surface of Bacillus subtilis 168 spores. Localization of β-Gal on the spore surface as a fusion to CotX was verified by western blot analysis, immunofluorescence microscopy, and flow cytometry. The optimum pH and temperature for the resulting spore-displayed β-Gal was 6.0 and 75℃, respectively. Under optimal conditions, it showed maximum activity of 0.42 U/mg spores (dry weight). Moreover, the spore-displayed CotX-β-Gal was employed as a whole cell biocatalyst to produce lactulose, yielding 8.8 g/l from 200 g/l lactose and 100 g/l fructose. Reusability tests showed that the spore-displayed CotX-β-Gal retained around 30.3% of its initial activity after eight successive conversion cycles. These results suggest that the CotX-mediated spore-displayed β-Gal may provide a promising strategy for lactulose production.

• Journal of Nutrition and Health
• /
• v.29 no.9
• /
• pp.1042-1048
• /
• 1996

In order to investigate heating rate of commercial milk products in korean market, lactulose content and availability of calcium and ascorbic acid were measured. The pH range for raw and commercial milk was 6.5-6.75, and protein content was 2.5-3.13%. The acid degree value (。SH)showed between 5.3 and 7.1. There were no differences in pH, protein and acid degree among 3 types of milk. The portion ionic Ca content in UHT-milk(32.4%) and pasteurized milk (27%) increased significantly in comparison with raw milk (4.6%). Pasteurization led to loss of 20% ascorbic acid, and losses of UHT-treatment are approximately twice as high. Significant differences of lactulose content between UHT milk and pasteurized milk were observed. Some of UHT milk products showed very high value of lactulose content like sterilized milk. It is well known that the stress caused by indirect UHT treatment is slightly higher compared with the direct process. The results in this experiment suggested that most of UHT milk in korean market may be treated by indirect UHT method. In oder to keep the adventages of milk component, the heating methods of milk have to be reconsidered.

• Korean Chemical Engineering Research
• /
• v.52 no.4
• /
• pp.407-412
• /
• 2014

Lactulose is well known for functional component in the food and pharmaceutical field and utilized in a wide variety of foods as a bifidus factor or functional ingredient for intestinal regulation. Lactulose synthesis can be classified into chemical and biological methods. In chemical methods, lactulose is synthesized by alkaline isomerization, but it has many disadvantages such as including product purification, lactulose degradation, side reactions and waste management. Therefore, the enzymatic synthesis methods were recently studied to solve these problems. ${\beta}$-galactosidase is a important enzyme in the dairy industry, because of the production of lactose-hydrolyzed products. Also, ${\beta}$-galactosidases can be utilized to synthesize lactulose from lactose by a trans-galactosylation reaction, using fructose as a galactosyl acceptor. However, the synthesis of lactulose from lactose is economically not suitable due to high levels of lactose price. This review summarizes the current state of lactulose production by chemical and biological processes.

• Microbiology and Biotechnology Letters
• /
• v.44 no.4
• /
• pp.504-511
• /
• 2016

Lactulose, a synthetic disaccharide, has received increasing interest because of its role as a prebiotic that can increase the proliferation of Bifidobacterium and Lactobacillus spp. and enhance the absorption of calcium and magnesium. While the industrial production of lactulose is still mainly achieved by the chemical isomerization of lactose in alkaline media, this process has drawbacks including the need to remove catalysts and by-products, as well as high energy requirements. Recently, the use of cellobiose 2-epimerase (CE) has been considered an interesting alternative for industrial lactulose production. In this study, to develop a process for enzymatic lactulose production using CE, we screened improved mutant enzymes ($CS-H^RC^E$) from a library generated by an error-prone PCR technique. The thermostability of one mutant was enhanced, conferring stability up to $75^{\circ}C$, and its lactulose conversion yield was increased by 1.3-fold compared with that of wild-type CE. Using a recombinant Escherichia coli strain harboring a CS35 $H^RC^E$-expressing plasmid, we prepared cell beads immobilized on a Ca-alginate substrate and optimized their reaction conditions. In a batch reaction with 200 g/l lactose solution and the immobilized cell beads, lactose was converted into lactulose with a conversion yield of 43% in 2 h. In a repeated 38-plex batch reaction, the immobilized cell beads were relatively stable, and 80% of the original enzyme activity was retained after 4 cycles. In conclusion, we developed a reasonable method for lactulose production by immobilizing cells expressing thermostable CE. Further development is required to apply this approach at an industrial scale.

• YAKHAK HOEJI
• /
• v.39 no.2
• /
• pp.169-174
• /
• 1995

By coculturing E. coli HGU-3 with Bifidobacterium KH-2 or Streptococcus faecalis HGO-7 with Bifidobacterium KH-2, the productivity of $\beta$-glucuronidase and $\beta$-glucosidase was inhibited. When lactulose, growth factor of lactic acid bacteria, was added into this medium, the productivity of these enzymes and pH of the medium were dramatically decreased. When intestinal microflora of human and rat were inoculated in the medium containing lactulose, the enyzme productivity and pH of the medium were dramatically decreased. By s.c. injecting DMH into mice, $\beta$-glucuronidase of intestinal bacteria was induced, but the production of the enzymes was inhibited by adminstering lactulose.