Analyzing Malodorous Compounds and Characteristics of Methanethiol Decomposing Bacteria

ﾒﾀﾝﾁｰｵｰﾙは硫黄系有機化合物であり､ppb のｵｰﾀﾞｰでも感知できる強い臭気を有する｡また､毒性を有し水溶性である｡したがって､水溶液中のﾒﾀﾝﾁｵｰﾙを簡便に測定することは非常に重要である｡これまでの研究で､水溶液中のﾒﾀﾝﾁｵｰﾙ濃度を測定するために既存の分析方法を改良して本研究に応用できることを報告している｡本分析法は､5,5ｼﾞﾁｵﾋﾞｽ(2ﾆﾄﾛ安息香酸､DTNB)がﾒﾀﾝﾁｵｰﾙと反応した生成物を 412nm の吸光度で測定するというｴｰﾙﾏﾝ反応に基づくものである｡ﾒﾀﾝﾁｵｰﾙの濃度は､吸光度に比例し､検量線にて容易に定量できた｡そして､微生物分解によるﾒﾀﾝﾁｵｰﾙ濃度の減少量を測定することにより､これらに適応可能かの評価を行い､水溶液中のﾒﾀﾝﾁｵｰﾙを測定することが有効であると判断できた｡本研究では､土壌から分離した菌を有効に利用することにより､脱臭商品や効率的な脱臭装置の開発が期待される｡そこで､分離した TOS-35 などのﾒﾀﾝﾁｵｰﾙ分解菌のﾌｨｰｼﾞﾋﾞﾘﾃｨｽﾀﾃﾞｨを行った結果､脱臭に関して可能性がある事が確認できた｡Methanethiol is a corrosive gas with a strong odor, and has the poisoning action resembled to hydrogen sulfide. It has the environmental toxicity and is soluble in water; therefore, it is very important to develop an easily measurable method for methanethiol in aqueous solutions. In this series of research, a fast and convenient analytical method was developed and applied to determine the concentration of methanethiol in aqueous solutions. It is based on the Ellman reaction, a reaction of methanethiol with 5,5\u27-dithiobis(2-nitrobenzoic acid)(DTNB), and the measurement of the absorbance of the product, namely quinoid anion, at 412 nm. The concentration of methanethiol was directly proportional to the absorbance at 412 nm, and a linear standard calibration curve was obtained in a certain range of concentration. In this research, an applicability of the new measurement method for the screening of methanethiol degrading bacteria was evaluated and it was found to be effective for measuring methanethiol in aqueous solution. As a result of the screening, TOS-35(Alcaligenes faecalis)demonstrated the highest ability of decomposing methanethiol and two feasibility studies were done in order to test the effectiveness of this bacterium

Controlling the Concentration of Malodorous Components in Kitchen Scraps

家庭内で発生する生ｺﾞﾐはそのままの状態で保管しておくと悪臭が発生する｡この悪臭は微生物の発生に起因するものと考えられ､微生物の増殖(腐敗)を阻害することで生ｺﾞﾐの悪臭発生の抑制が期待できる｡腐敗菌の増殖抑制手段として､温度､酸素濃度､二酸化炭素濃度､水分量などの環境制御因子が挙げられる｡今回の実験では､生ｺﾞﾐを保管する環境中の温度と酸素濃度を別々に制御して､生ｺﾞﾐの形態､外観､臭気がどのように変化するのかを調べ､生ｺﾞﾐの防臭手段にこれらが効果的なのかを検討した｡保管温度の点では､腐敗の激しい25℃に比較して､5℃と15℃ではｲｵｳ系化合物等の臭気成分濃度及び形態観察に顕著な差は見られなかったことから､15℃前後の保管温度の有効性が示唆された｡次に､酸素濃度の影響については､初期の酸素濃度を低くすることにより､生ｺﾞﾐ臭は弱くなると考えられ､特に､初期酸素濃度5%に設定したものが一番臭いが弱く効果的であることが分かった｡しかしながら､4日以上経過すると初期酸素濃度に関わらず､においの強さにはほとんど違いが見られなかった｡尚､初期酸素濃度0%の無酸素状態では10日以上経過しても外観は開始時とほとんど同一であった｡The emission of malodor by kitchen scraps is a serious problem in typical households, and thus preventing such malodor emission is crucial in achieving a healthy indoor environment. Upon disposing kitchen scraps, controlling environmental factors such as temperature, oxygen concentration, pH, osmotic pressure and the water content of food is effective in inhibiting microbial growth. This research was conducted focusing especially on the effects of temperature on the emission of malodorous compounds as food decays over time. Models of kitchen scraps were observed under three different temperatures:5℃, 15℃ and 25℃. The result showed that the model kept under 25℃ showed the highest concentration of malodorous components such as diacetyl, acetaldehyde, methyl mercaptan, ethyl mercaptan, propyl mercaptan and dimethyl disulfide. However, there was only a subtle difference between the models kept under 5℃ and 15℃. Therefore, in consideration of energy conservation, keeping kitchen scraps at 15℃ would be the most efficient means of preventing malodor emission. The second research was performed to examine how oxygen concentration affected the emission of malodorant from kitchen scraps under five different oxygen concentrations:0%, 5%, 10%, 15% and 20%. As a result, the model kept under 5% oxygen concentration had lower malodorous level;however, after about four days, there was no obvious difference among all the models