乳酸菌の1種L. gasseriは，全ゲノムの配列相同性に基づいて算出されるANI値をもとに近年分類の見直しが実施され，その一部がL. paragasseriとして再分類された．L. gasseriはD-アミノ酸を菌体外に生産する特徴を持つことから，D-アミノ酸生産に関与するアミノ酸ラセマーゼ遺伝子に着目し，L. gasseriとL. paragasseriの88のゲノム配列情報から，アラニンラセマーゼ，アスパラギン酸ラセマーゼ，およびグルタミン酸ラセマーゼをコードする遺伝子の塩基配列を比較した．その結果，アラニンラセマーゼ遺伝子alrとグルタミン酸ラセマーゼ遺伝子murIの塩基配列は，菌種依存的な制限酵素断片長多型（RFLP）を示すことが確認された．あらかじめrpoAおよびpheS遺伝子の塩基配列から菌種同定された菌株を使用して，alrおよびmurIを増幅してDraIおよびBamHIで制限酵素消化を行った結果，菌種依存的なRFLPを示すことが確認された．したがって，アラニンラセマーゼ遺伝子およびグルタミン酸ラセマーゼ遺伝子の制限酵素断片長多型を利用して，これら2種について迅速かつ簡便に菌種識別可能である．

熱安定性が高い食品タンパク質の一つとして知られている鶏卵白由来オボムコイドと未利用な加熱凝固性タンパク質の一つである米胚芽 γ グロブリンの食品学的機能特性の向上を目指した基礎研究を行った．

米胚芽 γ グロブリン，オボムコイド共存下での両者の相互作用性について，動的粘弾性測定，超音波分光分析，SEM観察，FT-IR分析およびSDS-PAGEを用いて探求した．その結果，米胚芽 γ グロブリン＋オボムコイド混合系は中性pHにおいて米胚芽 γ グロブリン単独タンパク質に匹敵する弾性率を有するゲルを形成することが判った．また，超音波分光分析により，混合ゲルにおいて，ゲル形成過程での水素結合の寄与が大きくなることなどが示された．

更に加熱処理前の超音波減衰値に基づく粒子サイズ解析および，SEMによるゲルの微細構造解析により，混合ゲルは，米胚芽 γ グリブリン単独ゲルに比べ小さい凝集体の集合により成っていることなどが示唆された．

以上のことから，オボムコイドは共存する熱凝固性タンパク質のゲル化特性にテクスチャーモディファイヤーとして影響を与えることが判った．今後は，本研究で行ったゲルのSEM観察に加え，共焦点レーザー走査顕微鏡観察なども併用し，混合タンパク質中での個々のタンパク質の存在状態などを可視化したいと考える．

The purpose of this study was to examine the effect of the application of eggshells to rice fields for calcium fortification on the quality of the cooked rice. The protein content and the amylose rate of each polished rice sample were not different from those of the control sample, and the taste analyzer values were almost the same. No clear difference in the calcium content of rice endosperm could be confirmed. However, the surface and overall hardness of the cooked rice grown with 100 or 200 kg of eggshell/10 a were increased in comparison to those of the control, and the stickiness of the surface also tended to be increased. Moreover, the characteristic value of the expansion volume of the cooked rice was increased, and it was inferred that the thermal behavior of the cell wall had changed, which affected the hardness and graininess of the cooked rice. In addition, the enzyme activity of the rice endosperm was lower than that of the control, and the absorbance at the maximum absorption wavelength of the iodine absorption spectrum of the eluted starch during cooking was increased. From these results, it was demonstrated that the application of eggshells to rice fields improved the graininess of the cooked rice and tended to increase the stickiness. It was also suggested that the effect of eggshell application on the cooked rice was not due to an accumulation of calcium in rice endosperm, but a complex and indirect effect on metabolic changes.

The main component of eggshells is calcium carbonate, which has been used for Ca research in rice cultivation in Japan. The effectiveness of Ca ions on rice was discovered in the 1 960 s by means of hydroponics, but the effect of Ca application on soil-grown rice has not yet been studied. The high-temperature ripening disorder of paddy rice in Japan in recent years is a sterility phenomenon caused by the failure of assimilation products produced in the leaves to be transferred to the ears. Therefore, to maintain the translocation of assimilated products produced in rice leaves, supplying Ca continuously even in small amounts is more important than increasing the Ca concentration in the plant. If research can be conducted on not only calcium carbonate, the main component of eggshells, but also the translocation rate of assimilates in paddy rice, and if high-temperature ripening disorders caused by weather conditions can be avoided, eggshells can be used as an agricultural material that contributes to food security in Japan.