Kimihiro Suzuki

Ultrasound-enhanced lactose hydrolysis in milk fermentation with Lactobacillus bulgaricus

The effects of ultrasonic irradiation during milk fermentation have been investigated in terms of the cell viability, β-galactosidase activity, the pH value of the culture medium, the degree of lactose hydrolysis and glucose content. The results showed that the ultrasonic irradiation caused the intracellular β-galactosidase to be released from the lactic acid bacteria cells. The released β-galactosidase showed a higher lactose hydrolysis activity than that in the cells. The β-galactosidase that was released to the medium has been more effectively used in pH-controlled fermentation. The results also showed that the continuous sonication caused the cell viability to decrease, but the viable cell count was again increased with static incubation after sonication. High degrees of lactose hydrolysis and high cell viabilities were obtained with the combination of pH-controlled sonicated fermentation and static incubation.

Effect of ultrasonic irradiation on production of fermented milk with Lactobacillus delbrueckii

Abstract Milk fermentation with Lactobacillus delbrueckii under ultrasonic irradiation was carried out in a 450 cm3 bioreactor with a polyethylene film bottom. Ultrasonic irradiation increased the hydrolysis of lactose in milk but decreased the cell viability. However, the viable cell count increased again when the ultrasound was stopped, because ultrasound did not destroy the ability for cell propagation. When the sonication power was 17.2 kW m-2 and the sonication period was 3 h, 4.9 × 108 cfu cm-3 of the viable cell count and 55% lactose hydrolysis were attained. In contrast, the viable cell count was 2 × 109 cfu cm-3 and 35.6% lactose was hydrolysed in control fermentation.

Synthesis of acrylic esters by lipase

Abstract Various acrylic esters were synthesized by the transesterification of vinyl acrylate with various alcohols. The yield of acrylic esters was about 40 and 66% with n-hexyl and β-phenethyl alcohol, respectively.

Cationic Graft Polymerization of 2-Oxazolines on Poly(vinyl alcohol) Derivatives

Abstract The graft polymerization of various monomers onto PVA has been studied by radical polymerization mechanism. Successful grafting of acrylonitrile (AN), acrylamide (AAm), acrylic acid, methyl methacrylate, and vinyl acetate was reported by using chemical (Minoet al., 1959; Ide, 1961; Maskimov et al., 1965) and radiation (Misra et al., 1987) methods. On the other hand, less attention has been paid to ionic graft polymerization. Sasson and Zilkha reported on grafting formaldehyde onto potassium-metallated PVA (Sasson and Zilkha, 1969). Galin studied grafting of AN and propane sulfone onto sodium-metallated PVA (Galin, 1971). We used the same anionic system for the polymerization of AAm (Ikeda and Suzuki, 1980).

PREPARATION OF ANTIMICROBIAL CELLULOSE DERIVATIVES

Epoxy-activated cellulose (CGE) was reacted with hexamethylenediamine (HMDA) and polyethyleneimine (PEI, Mw of 6.0 × 104) to give two aminated celluloses (HMDA- and PEI-celluloses) which were further utilized to prepare antimicrobial cellulose derivatives. Ampicillin (AMP) was immobilized on HMDA-cellulose with glutaraldehyde, and heavy metalions such as Ag (I), Hg (II), Cu (II), Cd (II) and Zn (II) were adsorbed on PEI-cellulose, and their antimicrobial activity were analyzed. The minimal inhibitory concentration (MIC) of AMP immobilized on cellulose was 68 μmol/L for Escherichia coli HB101 (E. coli) and less than 4 μmol/L for Bacillus subtilis Marburg 168 (B. subtilis) on the broth dilution method. On the other hand, PEI-cellulose bearing Ag (I), Hg (II), Cu (II) or Zn (II) ion showed higher antimicrobial activity for E. coli than that for B. subtilis. These effects were considered to be due to the liberation of antimicrobial agents from cellulose derivatives.

ANIONIC TRANSITION GRAFT-POLYMERIZATION OF ACRYLAMIDE ONTO RAYON

Rayon fibers were metallated with Li, Na and K methoxides in pure methanol or a mixed solvent consisting of CH3OH and dimethyl sulfoxide (DMSO) (1:1v/v) and the metallated fibers were allowed to react with acrylamide (AAm) in various solvents by the anionic mechanism to give graft copolymer with poly-β-alanine branches as well as polyacrylamide branches.Effects of a swelling pretreatment in water or DMSO, Na metallation time and medium, and methoxide concentration upon the degree of the metallation were investigated. The degree of Na metallation increased with CH3ONa concentration for the water- or DMSO-swollen rayon and the degree of metallation was higher for the latter. The higher degree of Na metallation was obtained on the exchange reaction with CH3ONa in the mixed solvent (1:1 CH3OH•DMSO) than in pure methanol at lower concentration of CH3ONa, and the degree of Na metallation of the DMSO-swollen rayon increased with the DMSO content in the mixed solvent.Effects of the AAm concentration, degree of metallation and reaction temperature upon the total graft-on and the graft-on via transition polymerization were investigated in various solvents. The total graft-on increased with the AAm concentration in the reaction solution for the Na metallated rayon. The graft-on via transition polymerization which was determined by the analysis of prim. amide nitrogen increased with the AAm concentration and was 8_??_34% of total graft-on. The graft-on was scarcely influenced by the addition of an inhibitor of radical polymerization into the reaction solution. Apparent activation energies of the graft-polymerization were 8_??_11kcal/mol for the Na metallated rayon fibers treated in various solvents. Both curves of the total graft-on and the graft-on via transition polymerization vs. the degree of metallation with Li, Na and K had maxima at 0.22_??_0.32mol/AGU (AGU: glucose unit) and their maximum values increased with an increase in the degree of swelling of the preswollen rayon, with a decrease in the dielectric constant of the solvent in the reaction solution and with an increase in the electropositivity of the alkali metal used.

CHANGE OF INTERNAL STRUCTURE OF POLYETHYLENE TELEPHTHALATE FIBRE BY THE TREATMENT WITH SOLVENTS

A commercial polyethylene terephthalate fibre (PET), drawn and heat-treated, was immersed in various solvents, the solvent diluted by water or methanol at 60°C for 4 hrs at the relaxed state, and the changes of the physical properties or the internal structure were measured with regard to the swelling, density, shrinkage, birefringence, and X-ray diffractions at wide or small angles. About fifty solvents tabulated in Table 1 with their chemical formulae and solubility parameters were used for the investigation. Immersion of PET in the solvents causes swelling and shrinking, resulting in the increases of density and crystallinity, while it decreases birefringence and orientation. The relation between the solubility parameter (δ) of the solvents and the physical properties is discussed. For each relation, two maxima or minima were observed at δ=9.7 and at 12.0. The results observed are attributed to the interaction between acidic solvent and the basic groups such as carbonyl of PET or between basic solvent and the acidic group such as methylene.Effects of water or methanol dilution on the properties of PET above mentioned were investigated. The change of properties with concentration was remarkable especially in the case of aqueous phenol solution.The effects of temperature (for two hrs) and time (at 150°C) of immersion in benzyl alcohol were also investigated.

Alkali-metallation of 6-Nylon and Anionic Graft-copolymerization of the Metallated Nylon with Acrylonitrile

6-Nylon fibres were metallated with Li, Na or K metboxide in methanol and the metallated fibres were allowed to graft-copolymerize with acrylonitrile(AN) in tetrahydrofuran(THF) or dimethyl sulfoxide(DMSO) by the anionic mechanism.Concerining the metallation of the nylon, effects of reaction time, methoxide concentration and reaction temperature upon the alkali metal combination onto the nylon were investigated. The equilibrium amounts of alkali metals combined increased linearly with methoxide concentrations and in the order of Li g Na g K. The metallation reactions were endothermic and the reaction heats were in the order of Li g Na g K. The apparent activation energies obtained were in the order of Li l Na l K.Concerning the graft-polymerization of AN onto the metallated nylons, effects of AN concentration, reaction time, alkali metal combination and reaction temperature upon the graftings were investigated in either medium of THF-AN or DMSO-AN. The graftings increased linearly with AN concentration in THF-AN medium, while they gave a maximum at AN 40-60 vol % in DMSO-AN medium. Apparent activation energies obtained were in the order of Li l Na l K in THF-AN medium, while in the order of Li g Na K O in DMSO-AN medium.The number average molecular weights ( Mn ) of the graft chains were measured, which were formed in DMSO-AN and separated after hydrolysis of the copolymers with 6 N HCI. From the calculated molecular weights and the measured ones, the following results were obtained: in the case of Li, initiator efficiencies were O.7-l.5 and Mn of the graft chains were 7000-llOOO, while in the case of Na or K, initiator efficiencies were 3-5 and Mn of the graft chains 2000-4000, provided that the initiator efficiency was the ratio of the calculated number average molecular weight to the measured one.