Kazuki Toeda

Large-Scale Production of Phospholipase D from Streptomyces racemochromogenes and Its Application to Soybean Lecithin Modification

Phospholipase D (PLD) catalyzes transphosphatidylation, causing inter-conversion of the polar head group of phospholipids and phospholipid hydrolysis. Previously, we cloned PLD103, a PLD with high transphosphatidylation activity, from Streptomyces racemochromogenes strain 10-3. Here, we report the construction of an expression system for the PLD103 gene using Streptomyces lividans as the host bacterium to achieve large-scale production. The phosphatidylcholine (PC) hydrolysis activity of S. lividans transformed with the expression plasmid containing the PLD103 gene was approximately 90-fold higher than that of the original strain. The recombinant PLD103 (rPLD103) found in the supernatant of the transformant culture medium was close to homogeneous. The rPLD103 was indistinguishable from the native enzyme in molecular mass and enzymatic properties. Additionally, rPLD103 had high transphosphatidylation activity on PC as a substrate in a simple aqueous one-phase reaction system and was able to modify the phospholipid content of soybean lecithin. Consequently, the expression system produces a stable supply of PLD, which can then be used in the production of phosphatidyl derivatives from lecithin.

Texture of Cooked Rice Prepared from Aged Rice and Its Improvement by Reducing Agents

The textures of cooked rice prepared from aged rice grains and their improvement by reducing agents were investigated. For aged rice that was stored for 5 months without air by the operation of a vacuum packing machine, the stickiness/hardness ratio of cooked rice was as low as that of aged rice stored in air. The results of electrophoresis showed that oxidation of proteins in the former was advanced to the same degree as in the latter. The stickiness/hardness ratios of the aged rice were increased by the addition of sodium sulfite, cysteine, and dithiothreitol to the cooking water. Sodium sulfite, cysteine, and dithiothreitol cleave disulfide bonds to sulfhydryl groups. Therefore, cleaving disulfide bonds to sulfhydryl groups improved the texture. The addition of them to the cooking water also increased the extractable solids at the time of heating. Hence cleaving disulfide bonds to sulfhydryl groups must increase extractable solids. Consequently, the gelatinized paste layer thickened and the thick paste layer softened the cooked rice.

Purification, biochemical characterization, and cloning of phospholipase D from Streptomyces racemochromogenes strain 10-3.

We previously isolated Streptomyces racemochromogenes strain 10-3, which produces a phospholipase D (PLD) with high transphosphatidylation activity. Here, we purified and cloned the PLD (PLD103) from the strain. PLD103 exerted the highest hydrolytic activity at a slightly alkaline pH, which is in contrast to the majority of known Streptomyces PLDs that have a slightly acidic optimum pH. PLD103 shares only 71–76% amino acid sequence identity with other Streptomyces PLDs that have a slightly acidic optimum pH; thus, the diversity in the primary structure might explain the discrepancy observed in the optimum pH. The purified PLD displayed high transphosphatidylation activity in the presence of glycerol, l-serine, and 2-aminoethanol hydrochloride with a conversion rate of 82–97% in a simple one-phase system, which was comparable to the rate of other Streptomyces PLDs in a complicated biphasic system.

Antimicrobial constituents of peel and seeds of camu-camu (Myrciaria dubia)

Various antimicrobial constituents of camu-camu fruit were isolated. Acylphloroglucinol (compound 1) and rhodomyrtone (compound 2) were isolated from the peel of camu-camu (Myrciaria dubia) fruit, while two other acylphloroglucinols (compounds 3 and 4) were obtained from camu-camu seeds. The structures of the isolated compounds were characterized by spectrophotometric methods. Compounds 1 and 4 were confirmed to be new acylphloroglucinols with different substituents at the C7 or C9 position of 2, and were named myrciarone A and B, respectively. Compound 3 was determined to be isomyrtucommulone B. This is the first report of the isolation of 3 from a natural resource. The antimicrobial activities of compounds 1, 3, and 4 were similar to those of 2, and the minimum inhibitory concentrations were either similar to or lower than that of kanamycin. These results suggest that the peel and seeds of camu-camu fruit could be utilized for therapeutic applications.

Components of essential oil of the Japanese mint ‘Hokuto’ and its deodorization effects against human malodors

ABSTRACT Japanese mint (Mentha arvensis var. piperascens Malinv. ex Holmes), ‘hokuto,’ is the highest-yield cultivar and contains a large amount of l-menthol in its essential oil. We focused on the dementholized oil of hokuto (hokuto DM oil), analysis of their aroma-active components and the potential deodorization effects against human malodors were demonstrated. The major components of hokuto DM oil were menthol, menthone, isomenthone and menthyl acetate. Among these, menthone, linalool, neoisomenthol, menthol and an unidentified compound were identified as the aroma-active components by AEDA. The deodorization activities of hokuto DM oil against four human malodors were measured by sensory evaluation and SPME-GC/MS analysis. Hokuto DM oil significantly deodorized isovaleric acid by a masking effect, with compounds containing a p-menthane skeleton, namely pulegone and menthone, found to contribute largely to the deodorant effects. These results demonstrate the possibility of using dementholized oil of Japanese mint as a freshening agent of toiletry products.

Data on volatile compounds produced by serotype D Clostridium botulinum

We analyzed the volatile compounds produced by serotype D Clostridium botulinum (D-CB16) in trypticase peptone/yeast extract/glucose (TYG) medium using gas chromatography/mass spectrometry (GC/MS). The volatile compounds were captured by solid-phase microextraction and applied to GC/MS for separation and identification of the compounds in TYG medium with or without the cultivation of C. botulinum D-CB16. Thirty-five and 34 volatile compounds were identified in media without and with D-CB16 cultivation, respectively. Of the compounds identified in the medium with the strain, twenty-one were not detected in the original medium, indicating that these were produced by C. botulinum D-CB16.

Data on the inhibitory effect of traditional plants from Sri Lanka against tyrosinase and collagenase

This article describes the inhibitory effects of extracts from 25 plants harvested in Sri Lanka against tyrosinase and collagenase. Inhibitors of these enzymes are common ingredients in cosmetics and medications, which help protect the skin against hyperpigmentation and premature aging. The article also discusses the polyphenol content of the extracts, which is well known to possess antioxidant properties. The extract data from the following plants, which have a long history in Sri Lankan traditional medicine, such as Ayurveda, have been provided: English name, “local name in Sri Lanka,” (scientific name). Indian copperleaf plant, “kuppameniya,” (Acalypha indica); red sandalwood, “madatiya”, (Adenanthera pavonina); balipoovu plant, “polpala,” (Aerva lanata); snap ginger, “heen araththa,” (Alpinia calcarata); bael fruit, “beli,” (Aegle marmelos); coastal waterhyssop, “lunuwila,” (Bacopa monnieri); porcupine flower, “katu karandu,” (Barleria prionitis); balloon-vine plant, “wel penera,” (Cardiospermum halicacabum); water caltrop, “Katupila,” (Flueggea leucopyrus); Indian sarsparilla, “iramusu,” (Hemidesmus indicus); malabar nut plant, “adhatoda,” (Justicia adhatoda); wood apple, “divul,” (Limonia acidissima); holy basil plant, “maduruthala,” (Ocimum tenuiflorum); emblic myrobalan plant, “nelli,” (Phyllanthus emblica); long pepper plant,”thippili,” (Piper longum); country borage plant, “kapparawalliya,” (Plectranthus amboinicus); common sesban, “wel murunga,” (Sesbania sesban); turkey berry, “gona batu,” (Solanum rudepannum Dunal); purple fruited pea eggplant,”welthibbatu,” (Solanum trilobatum); black plum, “madan,” (Syzygium cumini); crape jasmine, “wathusudda,” (Tabernaemontana divaricate); purple tephrosia, “pila,” (Tephrosia purpurea); Chinese chaste tree, “nika,” (Vitex negundo); and arctic snow, “suduidda,” (Wrightia antidysenterica). The inhibitory effects of these plant extracts on tyrosinase and collagenase, as well as polyphenol contents in the extracts, are detailed in Table 1.

Production of Arabinose from Corn Hull and Beet Pulp by High Pressure Steaming.

食品加工副産物であるコーンハルおよびビートパルプからの高温蒸煮によるアラビノースの効率的な生産法を検討した.その結果,コーンハルを処理圧力2～15Hkg/cm2で蒸煮すると,コーンハルから最大7.9%のアラビノースが遊離した.これはコーンハル中のアラビノースの63%に相当した.コーンハルの高圧蒸煮の際に燐酸(終濃度0.1M)を添加するとにより,アラビノースの生成量が増加し,その生成量はコーンハル中のアラビノースの82%に相当した.一方,ビートパルプを2～15kg/cm2で蒸煮すると,ビートパルプから最大6.6%のアラビノースが遊離した.これはビートパルプ中のアラビノースの30%に相当した.ビートパルプの高圧蒸煮においても燐酸(終濃度0.1M)を添加することにより,アラビノースの生成量が増加し,ビートパルプから最大16%のアラビノースが生成した.その生成量はビートパルプ中のアラビノースの72%に相当した.