Taku Miyamoto

Binding of Mutagens to Exopolysaccharide Produced by Lactobacillus plantarum Mutant Strain 301102S

Exopolysaccharide (EPS) was produced by Lactobacillus plantarum 301102 on exposure to the mutagenic action of acridine orange and novobiocin. The biological characteristics of this mutant strain 301102S were the same as those of the parent strain, but fermented milk prepared with the mutant strain showed antimutagenic activity on 3-amino-1,4-dimethyl-5H-pyrido indole. Only EPS-bound cells of strain 301102S showed binding ability to mutagens such as heterocyclic amines, and the mutagens were inactivated by binding to EPS. The binding ability was affected by pH; the greatest percentage binding was noted at pH 8.0. Addition of Mg(2+) and sodium dodecyl sulfate, but not oxgall, inhibited the binding ability. Therefore, the binding mechanism of the EPS may consist of ion-exchange and hydrophobic bonds, and the EPS would bind mutagens in the intestine.

Interaction between lactic acid bacteria and yeasts in airag, an alcoholic fermented milk

The interaction between nine lactic acid bacteria (LAB) and five yeast strains isolated from airag of Inner Mongolia Autonomic Region, China was investigated. Three representative LAB and two yeasts showed symbioses were selected and incubated in 10% (w/v) reconstituted skim milk as single and mixed cultures to measure viable count, titratable acidity, ethanol and sugar content every 24 h for 1 week. LAB and yeasts showed high viable counts in the mixed cultures compared to the single cultures. Titratable acidity of the mixed cultures was obviously enhanced compared with that of the single cultures, except for the combinations of Lactobacillus reuteri 940B3 with Saccharomyces cerevisiae 4C and Lactobacillus helveticus 130B4 with Candida kefyr 2Y305. C. kefyr 2Y305 produced large amounts of ethanol (maximum 1.35 g/L), whereas non-lactose-fermenting S. cerevisiae 4C produced large amounts of ethanol only in the mixed cultures. Total glucose and galactose content increased while lactose content decreased in the single cultures of Leuconostoc mesenteroides 6B2081 and Lb. helveticus 130B4. However, both glucose and galactose were completely consumed and lactose was markedly reduced in the mixed cultures with yeasts. The result suggests that yeasts utilize glucose and galactose produced by LAB lactase to promote cell growth.

Distinctive proteolytic activity of cell envelope proteinase of Lactobacillus helveticus isolated from airag, a traditional Mongolian fermented mare's milk☆

Airag is a traditional fermented milk of Mongolia that is usually made from raw mares milk. Lactobacillus helveticus is one of the lactic acid bacteria most frequently isolated from airag. In this study, we investigated the genetic and physiological characteristics of L. helveticus strains isolated from airag and clarified their significance in airag by comparing them with strains from different sources. Six strains of L. helveticus were isolated from five home-made airag samples collected from different regions of Mongolia. The optimal temperature for acidification in skim milk was 30 to 35°C for all the Mongolian strains, which is lower than those for the reference strains (JCM 1554 and JCM 1120(T)) isolated from European cheeses. All of the strains had a prtH1-like gene encoding a variant type of cell envelope proteinase (CEP). The CEP amino acid sequence in Snow Brand Typeculture (SBT) 11087 isolated from airag shared 71% identity with PrtH of L. helveticus CNRZ32 (AAD50643.1) but 98% identity with PrtH of Lactobacillus kefiranofaciens ZW3 (AEG40278.1) isolated from a traditional fermented milk in Tibet. The proteolytic activities of the CEP from SBT11087 on artificial substrate (N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide) and pure casein were measured using an intact-cell degradation assay. The activity of the CEP from SBT11087 was observed to be weak and exhibited a lower optimal temperature (40°C) than those from the reference strains (45-50°C). The specificity of the SBT11087 CEP for αS1-casein was typical of the CEPs previously reported in L. helveticus, as determined through the degradation profiles obtained through gel electrophoresis and mass spectrometry analyses. In contrast, the degradation profile of β-casein revealed that the CEP of SBT11087 primarily hydrolyzes its C-terminal domain and hydrolyzed nine of the 16 cleavage sites shared among the CEPs of other L. helveticus strains. Thus, the CEP of SBT11087 is distinct from those from previously reported L. helveticus strains in terms of its optimal temperature and its degradation of β-casein. Therefore, the Mongolian L. helveticus strains differ from other strains of the species in different collections and are specifically suited for the natural lactic acid bacterial population in airag.

Draft Genome Sequence of Leuconostoc mesenteroides 406 Isolated from the Traditional Fermented Mare Milk Airag in Tuv Aimag, Mongolia

ABSTRACT Leuconostoc mesenteroides 406 was isolated from the traditional fermented mare milk airag in Tuv Aimag, Mongolia. This strain produces an antilisterial bacteriocin. Here, we report the draft genome sequence of this organism.

Draft Genome Sequence of Leuconostoc mesenteroides 213M0, Isolated from Traditional Fermented Mare Milk Airag in Bulgan Aimag, Mongolia

ABSTRACT Leuconostoc mesenteroides 213M0 was isolated from traditional fermented mare milk airag in Bulgan Aimag, Mongolia. This strain produces a listericidal bacteriocin-like inhibitory substance. Here, we report the draft genome sequence of this organism.

Influences of vitamin E supplementation on the meat color stability of Jersey cows.

ジャージー種雌牛肉について,ミオグロビンのメト化による肉色の褐色化を抑制するため,肥育時にビタミンEを給与し,その効果を検討した.食肉用に肥育されたジャージー種雌牛に対して,出荷前平均78日間,1,000mg/頭/日のビタミンEを給与し,大腿二頭筋と胸最長筋を採取した,各筋肉をステーキ状に整形して4°C,暗所で120時間保存し,その間の筋肉表面のメトミオグロビン割合を測定した,大腿二頭筋において,ビタミンE給与によりメト化が抑制された(P<0.05).筋肉中のビタミンE含量は給与期間が長いほど高く,含量が高いほどメト化抑制効果が認められた.また,安定した肉色保持効果を期待するには,少なくとも90日以上の給与が必要と考えられた.一方,胸最長筋では給与区が対照区と比べて,その差は小さいもののメト化が進行し,ビタミンEの給与による肉色安定効果は筋肉部位により違いがあることが認められた.

Intrageneric Conjugal Transfer of Lactose Plasmid DNA in Lactococcus lactis subsp. lactis NIAI 527.

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Use of Pediococcus acidilactici transferred lactose-fermenting and protein-hydrolyzing abilities via conjugation to fermented milk

ラクトース発酵性およびプロテアーゼ活性がない(Lac- Prt-)ため牛乳中での生育がみられず,従来,乳業用乳酸菌とは考えられていなかったPediococcus acidilacticiから,著者らは接合法を用いて牛乳中で生育可能なLac+ Prt+ P. acidilactici (Lac+ Prt+交配菌)を作出した.本研究では,そのLac+ Prt+交配菌の脱脂乳培地における芳香生産性と生酸性を試験し,発酵乳を作るための培養条件を検討した.その結果,Lac+ Prt+交配菌は良好な芳香生産性を示し,脱脂乳培地を凝固した.しかし,培地の凝固には36時間を要した.一方,生酸性において脱脂乳培地中のグルコースおよび無脂乳固形分の影響を検討したが,滴定酸度は0.85%(発酵乳の嗜好上,至適乳酸酸度)に及ばなかった.そこで,発育の促進を図るためフィルター滅菌したシイタケジュースを添加したところ,培地の凝固時間および生酸性は著しく改善された.以上のような検討結果から,Lac+ Prt+交配菌を用いた実用的な発酵乳の製造条件を決定した.すなわち,12%還元脱脂乳に8%量のショ糖を加えて殺菌した後,フィルター滅菌したシイタケジュースを1%量添加する.このミックスにLac+ Prt+交配菌を2%量接種し,30°Cで16～18時間培養することによって発酵乳が製造できた.つまり,P. acidilacticiの牛乳への利用が可能になったものと思われた.一方,このLac+ Prt+交配菌は発酵乳製造60日以上も安定した滴定酸度(約0.9%)と生菌数(106/mlレベル)を保持し,また法Pediococcus属細菌由来の耐塩性(8～9%NaCl)をもつことから,今後,チーズスターターへの利用も期待される.

Evaluation of genetic factors of lactose intolerance in rats.

本実験では, wistar系ラットを用いて, 乳糖分解吸収能の年齢的消長をLTTで調べ, さらに, この系統におけるLTT時の血糖上昇量, ラクターゼ活性の遺伝率を推定し, これらを指標として乳糖不耐症における遺伝要因について検討した。また, 各選抜群における他の二糖類分解酵素活性, 乳糖負荷後の臨床症状としてふん中水分量, ふん中の還元糖の有無について検討を加えた。得られた結果は以下の通りである。1) LTT時における血糖上昇量は, 5週齢から6週齢以降急激に低下することが認められ, 低下の程度, 低下しはじめる時期に個体差の大きいことが認められた。2) 11週齢時のLTTにおける血糖上昇量によって40mg/dl以上をH群, 29mg/dl以下をL群および30～39mg/dlをM群とした。このような3群に分けた場合のLTT時の血糖上昇量の週齢に伴う推移は, L群では5週齢から6週齢以降急激に低下するのに対し, H群では, 低下の程度は少なくほぼ6週齢時の値を維持し, M群は, 両群の中間の値を示すことが認められた。3) このようなH, L群間においてラクターゼ活性に有意差が認められた (p<0.05)。また, LTT時の血糖上昇量とラクターゼ活性との間には, 有意な相関がみられた (r=0.69)。4) LTT時の血糖上昇量とラクターゼ活性の遺伝率は, それぞれ0.736～0.799および0.403～0.624の値が推定された。5) 選抜に伴うLTT時の血糖上昇量の推移は選抜2世代でH群が40.5, L群が16.5mg/dlを示した。ラクターゼ活性は2世代でH群が16.4, L群が11.4unit/g. proteinを示した。このように, LTT時の血糖上昇量, ラクターゼ活性ともH群は高いほうへ, L群は低いほうへ選抜されていることが示された。6) グルコース+ガラクトース+エタノール負荷試験における血中ガラクトースおよびダルコース値の変化は選抜各世代のLおよびH群間で差は認められなかった。7) 0.75～2.5g/kgの各乳糖量を負荷した場合の下痢症状の発現は, 1.5g/kg以上でL群に軟便が認められ, 負荷乳糖量が多いほどL群で軟便を呈するものが増加した。各乳糖量を負荷した際の血糖値の変化では, 両群とも負荷乳糖量が増加すると負荷後の血糖値も高くなり, 最大値に達する時間が遅くなる傾向がみられた。8) 二糖類分解酵素活性は, ラクターゼ活性において, L群がH群に比べて有意に低い値 (p<0.05) を示したのに対し, スクラーゼおよびマルターゼ活性は, L群がH群に比べて低い値を示す傾向にあった。しかし, 各群間に有意差は認められなかった。以上のことから, slc-Wistarラットにおいて, 乳糖の分解吸収能には, 遺伝の関与の大きいことが示唆された。さらに, 乳糖負荷時の血糖上昇量およびラクターゼ活性を指標とした選抜によって, 乳糖の分解吸収能の異なった系統作出の可能性が示唆された。

Isolation from Soy Milk of a Growth-stimulating Substance for Lactic Acid Bacteria

A growth-stimulating substance for specific lactic cultures such as Lactobacillus casei and Lactobacillus acidophilus was isolated from a precipitate fraction of soybean whey which was followed by ethanol fractionation , and some properties of the substance were investigated. Crude preparation fractionated with ethanol was passed through sulphopropyl-Sephadex C-25 and was resolved into at least three active growth stimulatory fractions of Lactobacillus casei subsp. alactosus 34143 used as the test organism of microbiological assays . One of the fractions, which showed the highest activity , was homogenous and ninhydrin positive. From the results of UV absorption spectrum and amino acid analysis, the purified growth-stimulating substance was considered to be peptide and its molecular weight 1,150 daltons . Jpn. J. Zootech. Sci., 58 (9): 754-763 , 1987