• Journal of Microbiology and Biotechnology
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• v.1 no.3
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• pp.151-156
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• 1991

In order to construct a yeast strain having high ethanol tolerance together with good lactose fermentation ability, the protoplast fusion using Saccharomyces cerevisiae STV 89 and Kluyveromyces fragilis CBS 397 was carried out. Auxotrophic mutants of K. fragilis were obtained as a selection marker by treatment of ethylmethane sulfonate. The best mutant for protoplast fusion was selected based on the capabilities of ${\beta}-galactosidase$ production and lactose fermentation. The protoplast fusion using polyethylene glycol and calcium chloride solution led to the fusion frequence of $3{\times}10^{-6}$ and a number of fusants were obtained. Among these fusants, a fusant F-3-19 showed the best results in terms of ethanol tolerance, ${\beta}-galactosidase$ activity and lactose fermentation. The performance of lactose fermentation and ethanol tolerance by this fusant were better than those of K. fragilis. Study on the ethanol tolerance having relation to fatty acid composition and intracellular ethanol concentration revealed that the fusant F-3-19 had a higher unsaturated fatty acids content and accumulated less amount of intracellular ethanol compared with a parent of K. fragilis.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1996.04a
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• pp.283-283
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• 1996

The hydrolyzed-lactose milk for the lactase-deficient subject is sweeter than whole milk, and some subjects dislike its taste. To overcome this shortcoming the dried liposomes containing ${\beta}$-galactosidase to digest lactose in milk after drinking were prepared and examined the possible application of this dried liposomes to the lactase-deficient subjects. To improve the stability of conventional liposome suspension, the dried liposomes in the presence of trehalose were prepared by the dehydration-rehydration vesicles method. Small unilamellar vesicles, prepared with egg phosphatidyl cholesterol, and cholesterol, were mixed with ${\beta}$-galactosidase solution and then ;up[jo;ozed. The freeze-dried liposome was rehydrated and centrifuged. The resultant multilamellar vesicles were mixed with trehalose(4g/g lipid) and then lyophilized to produce final dried liposome. Trehalose increased the entrapping efficiency of liposomes by 3 fo1d compared to the liposomes without trehalose (13% vs. 46%).

• Journal of Microbiology and Biotechnology
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• v.4 no.2
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• pp.155-159
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• 1994

Two Zymomonas mobilis strains (ZM63 and ZM6307), containing both lactose and galactose operons, were constructed. $\beta$-Galactosidase and galactokinase assays indicated that both operons were expressed in both strains. The transport systems available for lactose uptake by Zymomonas mobilis were investigated using $^{14}C$-labelled lactose. After the outer membrane, which was considered to be a possible barrier to lactose uptake, was disrupted by treatment with EDTA and $Ca^{2+}$ ions, some increase in lactose uptake was observed in ZM6306 ($lac^+$) and ZM6307 ($lac^+\;gal^+$), but not in the parent, ZM6. This suggested that the outer membrane of Zymomonas mobilis acts as a barrier to lactose uptake to some degree, and also that the lactose permease is operational in Zymomonas mobilis.

• Applied Biological Chemistry
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• v.38 no.6
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• pp.502-506
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• 1995

A Bacillus strain which produces ${\beta}-galactosidase$ with high transgalactosylation activity, was isolated from soil and tentatively designated as Bacillus sp. A1. When ${\beta}-galactosidase$ from Bacillus sp. A1 reacted with 40% (w/w) lactose, transgalactosylation ratio reached up to 90% at the 70% conversion of the initial lactose. The biosynthesis of the enzyme in Bacillus sp. A1 required lactose as an inducer and was repressed by glucose. Observing that the addition of amino acids to culture medium resulted in enhancing, to a significant extent, both the growth and the enzyme production of the strain, yeast extract and commercially available hydrolysates of protein were examined for the suitability as amino acid source. As it turned out, SMP, an enzymatic hydrolysis product of soybean protein from Fuji Oil Co.(Japan), was the most suitable for optimization of the culture medium. When Bacillus sp. A1 was cultured in the presence of 0.5% SMP and 2% lactose, the enzyme activity increased up to $1.8\;U/m{\ell}-broth$.

• Journal of Life Science
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• v.26 no.12
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• pp.1477-1486
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• 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
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• v.29 no.5
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• pp.566-572
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• 2009

This study was designed to elucidate the quantities of milk nutrients entrapped during cholesterol removal from milk by crosslinked $\beta$-cyclodextrin ($\beta$-CD, 0.4~1.2%, w/v) and to evaluate the amounts of the residual $\beta$-CD in cholesterol-reduced milk treated by crosslinked $\beta$-CD. The content of lactose in the control milk (without treatment by crosslinked $\beta$-CD) was 4.86%, and the amounts of lactose entrapped by crosslinked $\beta$-CD ranged from 0.00 to 0.03%. The total amounts of the entrapped short-chain free fatty acid (FFA) and free amino acid (FAA) ranged from 0.03 to 0.09 ppm and from 0.28 to $0.71{\mu}mol/mL$, respectively. The amounts of the entrapped water-soluble vitamins (L-ascorbic acid, niacin, thiamine and riboflavin) ranged from 0.02 to 0.05 ppm, 0.01 to 0.06 ppm, 0.00 to 0.06 ppm and 0.01 to 0.06 ppm, respectively. The entrapped amounts of lactose, short-chain FFAs, FAAs and water-soluble vitamins were not remarkably affected by the concentrations of crosslinked $\beta$-CD (0.4~1.2%, w/v). Only very small amounts of residual $\beta$-CD in the cholesterol-removed milk were measured (1.22~3.00 ppm). Based on the data obtained from the present study, it was concluded that the amounts of entrapped nutrients were negligible during cholesterol removal from milk by crosslinked $\beta$-CD, and only trace amounts of residual $\beta$-CD were present in cholesterol-removed milk.

• Korean Journal of Food Science and Technology
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• v.27 no.3
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• pp.271-280
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• 1995

These studies examined the production of oligosaccharides by ${\beta}-galactosidase$originated from Aspergillus oryzae and Kluyveromyces fragilis mixed. In addition, heat resistance and acid stability of transgalactosylated oligosaccharides were measured. When ${\beta}-galactosidase$ from A. oryzae, K. fragilis and mixed ${\beta}-galactosidase$ were added to 30%(w/v) lactose solution, maximum production of transgalactosylated oligosaccharides were 26.9%, 37.05 and 27.2%, respectively. The ratios of disacchride, trisacchride and tetrasaccharide in transgalactosylated oligosaccharides were 20.5 : 5.4 : 0.6, 20.4 : 10.5 : 4.2 and 21.0 : 4.1 : 1.9, respectively. Nine different oligosaccharides were recovered with 30% and 40% ethanol fractions. When the 30% ethanol fraction was treated at $150^{\circ}C$ for 10 min more than 90% of oligosaccharides remained stable. More than 90% of the oligosaccharides were stable at $130^{\circ}C$ for 3 min with pH 3.0, whereas there of Kluyveromyces was more than 90% with pH 3.5.

• Microbiology and Biotechnology Letters
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• v.11 no.3
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• pp.205-210
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• 1983

Extracellular $\beta$-galactosidase was prepared from a culture of Lactobacillus sporogenes, a spore-forming lactic acid bacterium. The enzyme functioned optimally at pH 6.8 and at 6$0^{\circ}C$ o-nitrophenyl-$\beta$-D-galactopyranoside (ONPG) in 0.05M sodium phosphate buffer. The activation energy of the enzymatic hydrolysis of ONPG was about 16,000 cal/mole below $50^{\circ}C$ and 11,300 cal/mole above the temperature. It was fairly stable over a pH range from 4.0 to 8.0 losing only less than 30% of its activity after hearting at 6$0^{\circ}C$ and pH 6.8 for 3 hours. Metal ions showed no significant effect on the enzyme activity, whereas L-cysteine exerted a slight stimulatory effect at the concentration of 10mM. The km values were 1.48mM for ONPG and 64.5mM for lactose. Hydrolysis of ONPG by the enzyme was product-inhibited by galactose (Ki=13.3mM, competitive inhibition) and by glucose(Ki= 11.4mM, uncompetitive type). The enzyme activity was also noncompetitively inhibited in the presence of lactose (Ki= 17.8mM).

• Microbiology and Biotechnology Letters
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• v.13 no.4
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• pp.355-359
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• 1985

The purified $\beta$-galactosidase from L. sporogenes was most active at pH 7.0 and 6$0^{\circ}C$ with O-nitrophenyl-$\beta$-D-galactopyranoside (ONPG) in 0.05 M phosphate buffer. It was stable over a pH range from 5.0 to 9.0 and lost less than 10％ of its activity after heating for 30 minutes at 6$0^{\circ}C$ and pH 7.0. All the mineral ions examined in this work showed no significant activating effect, whereas L-cysteine exerted a great stimnlatory effect on the enzyme activity at the concentration of 10 mM. The Km values were 1.2 mM for ONPG and 33.3 mM for lactose. Approximately 85％ of lactose in cow's milk, in 10％ skim milk and in 5％ lactose solution was hydrolyzed after 4 hours incubation at 6$0^{\circ}C$ with 2 units of the purified $\beta$-galactosidase per $m\ell$ of the substrate solutions. The $\beta$-galactosidase from L. sporogenes, therefore, is considered to be suitable for hydrolysis of lactose in milk and other dairy products.

• Applied Biological Chemistry
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• v.41 no.7
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• pp.500-504
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• 1998

The enzymatic transgalactosylation of L-ascorbic acid was investigated to synthesize a chemically stable form of L-ascorbic acid by using commercially available ${\beta}-galactosidases$. Among various enzymes examined, Aspergillus oryzae ${\beta}-galactosidase$ was found to be formed the derivative of ascorbic acid in a high yield from ascorbic acid and lactose. The reaction product was isolated by ion exchange chromatography on a $Dowex\;1\;{\times}\;8$ (Cl - form) resin and Toyopearl HW-40S gel chromatography. The product was identified as $6-O-{\beta}-_D-galactopyranosyl-_L-ascorbic\;acid$ on the basis of various experimental results, viz., UV, IR, $^1H-NMR,\;^{13}C-NMR$ and mass spectral data.