Studies on lactic acid bacteria having antimutagenicity toward N-nitroso compounds

饮食中的诱变和致癌抑制剂尤其令人感兴趣，因为它们可能对人类癌症预防有用。因此，乳酸菌在发酵乳中具有很高的营养、治疗、抗肿瘤和抗癌功能。最近的研究表明，乳酸菌对n -亚硝胺等多种诱变剂/致癌物也具有抗诱变活性。在本研究中，我们首先检测了从“dadih”和“kefir”中分离的乳酸菌的结合能力，这两种乳酸菌分别来自印度尼西亚和蒙古的发酵乳制品。所有分离株对诱变色氨酸热解产物Trp-P1和Trp-P2均表现出较高的结合能力。其中，乳酸乳球菌亚种。lactis T-80对这些诱变剂的结合能力最强，但随着胰蛋白酶浓度的增加，结合能力降低。T-80菌株与这些诱变剂的结合机制被认为是由于形成疏水性键。作为实验的第二部分，我们以鼠伤寒沙门氏菌TA 98链霉素依赖菌株（sd510）为指示菌，检测了上述发酵乳制品中分离的乳酸菌对n-亚硝基sopiperidine （NPIP）、n-亚硝基二甲胺（NDMA）、n-亚硝基二乙胺（NDEA）和n-亚硝基sopyrolidine （NPYR）等n-亚硝胺的抗诱变性。40株菌株对NDEA和NDMA表现出抗诱变活性，但对NPIP和NPYR没有抗诱变活性。

Dietary inhibitors of mutagenesis and carcinogenesis are of particular interest, because they may be useful for human cancer prevention. In respect with that view, lactic acid bacterial strain encountered in fermented milk are being known to have high value in nutritional, therapeutic, antitumor as well as anticancer functions. Recent findings have shown that lactic acid bacteria also performed antimutagenic activity against various kinds of mutagens/carcinogens such as N-nitrosamins.In the present research, we first examined binding abilities of lactic acid bacteria isolated from "dadih" and "kefir" , which are fermented milk products in Indonesia and Mongolian, respectively. All the isolates exhibited high binding abilities toward mutagenic tryptophane pyrolysates, viz., Trp-P1 and Trp-P2. Among them, Lactococcus lactis subsp.lactis T-80 exhibited the highest binding ability toward such mutagens, but the binding decreased with the increase of trypsin concentration. The mechanism of binding of the T-80 strain with such mutagens was supposed to be due to the formation of hydrophobic bonds.As a second part of experiment, we examined antimutagenicity of the lactic acid bacteria isolated above mentioned fermented milk products toward N-nitrosamines, viz., N-nitrosopiperidine (NPIP) , N-nitrosodimethylamine (NDMA) , N-nitrosodiethylamine (NDEA) and N-nitrosopyrolidine (NPYR) using a Salmonella typhimurium TA 98 streptomycin-dependent strain (SD 510) as an indicator bacteria. 40 strains examined exhibited antimutagenic activity against NDEA and NDMA,but not against NPIP and NPYR.