熱量測定法によるクロロアセトン超音波分解生成物の酵母に対する毒性評価

摘要

Many kinds of toxic compounds are emitted in the environment from human activity. It has already been reported that various compounds can be decomposed by ultrasonic irradiation. However, there have been few studies regarding the toxicity of the compounds produced by sonochemical decomposition. Therefore, it is important to investigate the effects of sonochemical decomposition products on environmental microorganisms. In this study, the growth activity of yeast cells in growth media containing toxic compounds and their sonochemical decomposition products was measured by a calorimetric analysis. The calorimetric analysis could provide not only quantitative information for the microbial growth activity, but also the characteristic features about the bactericidal and bacteriostatic effects of the chemicals on microbial cells. The growth curves of yeast cells, measured by calorimetry, showed that chloroacetone (MCA) affected the growths of yeast cells. In addition, in the presence of MCA of over 450 ppm, the growth of yeast cells could not be observed. In the case of the sonochemical decomposition products of MCA (initial concentration; 500 ppm), the peak of growth thermograms of yeast cells shifted towards a shorter incubation time. The growth curve of the cells with 6 hours sonicated sample of MCA was similar to that observed without MCA, suggesting that the toxicity of MCA on the growth of yeast cells decreased according to the decomposition of MCA.%超音波化学反応は有害有機物質の分解・無害化に有効であることが報告されているが，有害有機物質の無害化においては何らかの副生成物の生成が示唆される．しかし，超音波分解生成物の詳細な同定やそれらが 実際に生物に対し無害であるかどうかについての研究報告はほとんどないのが現状である．そこで本研究では，水処理過程で発生するクロロアセトンの毒性とその超音波分解過程での毒性を酵母の増殖速度及び増殖 挙動における代謝熱量から解析する熱量測定法で評価した．熱量測定法では，一般的に微生物の評価に用いられるコロニー計数法と比較すると，微生物の増殖動態を定量的かつ定性的に評価できることが示唆された．