Abstract
BackgroundThe effects of enterolignans, e.g., enterodiol (END) and particularly its oxidation product, enterolactone (ENL), on prevention of hormone-dependent diseases, such as osteoporosis, cardiovascular diseases, hyperlipemia, breast cancer, colon cancer, prostate cancer and menopausal syndrome, have attracted much attention. To date, the main way to obtain END and ENL is chemical synthesis, which is expensive and inevitably leads to environmental pollution. To explore a more economic and eco-friendly production method, we explored biotransformation of enterolignans from precursors contained in defatted flaxseeds by human intestinal bacteria.ResultsWe cultured fecal specimens from healthy young adults in media containing defatted flaxseeds and detected END from the culture supernatant. Following selection through successive subcultures of the fecal microbiota with defatted flaxseeds as the only carbon source, we obtained a bacterial consortium, designated as END-49, which contained the smallest number of bacterial types still capable of metabolizing defatted flaxseeds to produce END. Based on analysis with pulsed field gel electrophoresis, END-49 was found to consist of five genomically distinct bacterial lineages, designated Group I-V, with Group I strains dominating the culture. None of the individual Group I-V strains produced END, demonstrating that the biotransformation of substrates in defatted flaxseeds into END is a joint work by different members of the END-49 bacterial consortium. Interestingly, Group I strains produced secoisolariciresinol, an important intermediate of END production; 16S rRNA analysis of one Group I strain established its close relatedness with Klebsiella. Genomic analysis is under way to identify all members in END-49 involved in the biotransformation and the actual pathway leading to END-production.ConclusionBiotransformation is a very economic, efficient and environmentally friendly way of mass-producing enterodiol from defatted flaxseeds.
Highlights
The effects of enterolignans, e.g., enterodiol (END) and its oxidation product, enterolactone (ENL), on prevention of hormone-dependent diseases, such as osteoporosis, cardiovascular diseases, hyperlipemia, breast cancer, colon cancer, prostate cancer and menopausal syndrome, have attracted much attention
When the cultures were terminated, END could be detected in media A and B, but not C, with the yield of END in medium B being considerably higher than that in medium A (Fig. 2). These results indicated that a nitrogen source (NH4Cl in this study, present in B but not in C) was necessary to support the bacteria that could transform flaxseed lignans into END
Optimization of culture conditions for large-scale production of END For large-scale production of END, we increased the volume of medium B from 3 ml to 2 liter with 40 g defatted flaxseeds in 4 liter Erlenmeyer flasks
Summary
The effects of enterolignans, e.g., enterodiol (END) and its oxidation product, enterolactone (ENL), on prevention of hormone-dependent diseases, such as osteoporosis, cardiovascular diseases, hyperlipemia, breast cancer, colon cancer, prostate cancer and menopausal syndrome, have attracted much attention. In the 1980s, enterodiol (END) and enterolactone (ENL) were first detected in the serum, urine and bile of humans and several animals [1,2]. They were classified as phytoestrogens due to their origins from plants and their estrogenic as well as antiestrogenic activities in humans. Numerous studies have indicated that END and ENL can be produced from several plants, such as flaxseed, by bacteria in the intestinal tract of humans and animals. Thompson et al tested 68 common plant foods and found that flaxseed flour and its defatted meal produced the highest yield of END and ENL in vitro, up to 800 times higher than that from others [8]
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