Soy Tempeh Deters E. Coli, Promotes Gut Health
New research has determined that tempeh – an ancient fermented soybean food – has the ability to stimulate increased colonies of intestinal probiotics and decrease pathogenic bacteria such as E. coli.
The researchers, from Poland’s Institute of Food Technology of Plant Origin and Poznań University of Life Sciences, studied the effects of two kinds of tempeh side by side – soy tempeh and bean tempeh. They also compared the results with cooked but not fermented soybeans and bush beans.
Within their laboratory, the researchers duplicated the environment of the intestines, with the inclusion of probiotics and bile acids. The researchers prepared fermented soy tempeh and bean tempeh according to traditional methods, utilizing the yeast strain Rhizopus oligosporus to ferment the beans.
The researchers followed traditional production methods. After hulling the soybeans and the beans – common bush beans (Phaseolus vulgaris) – they fermented them separately at 37 degrees Celsius (about 98.6 F) for 24 hours. They blended each batch and divided them up. One of each of the tempehs were then cooked, and one of each of the tempehs was fried. The researchers also prepared cooked soy and cooked beans as controls the tempehs as one would fry a tempeh burger before eating it.
The researchers began testing the two tempehs side by side. In one test, the researchers studied the growth of several types of intestinal bacteria: Bacillus subtilis, Escherichia coli, Lactobacillus acidophilus and Lactobacillus paracasei. The former two of which are known pathogens, and the later two are healthy probiotics. The researchers also studied colonies of Bifidobacteria as well.
The researchers found that within the duplicated intestinal medium, the soybean tempeh stimulated colonies of the Lactobacilli, as well as stimulated colonies of Bifidobacteria. The soy tempeh also reduced E. coli and Enterococcus species within the intestinal environment.
Meanwhile, the researchers found that the bean tempeh wasn’t able accomplish the same results as the soy tempeh – even though both were fermented and prepared the same.
The researchers found that the bean tempeh stimulated greater colonies of Escherichia coli and Enterococcus species n the intestinal chamber. The fried bean tempeh did reduce Enterococcus species slightly compared to cooked unfermented beans, but nowhere near the extent of the soybean tempeh.
The study proved that not only does the fermentation process produce antibiotic effects in soybean tempeh products, but much of these effects are specific to soybeans. While the bean tempeh performed better than cooked unfermented beans in terms of stimulating lactobacilli and bifidobacteria, they did not achieve much if any antibacterial effect in the intestines, as the soybean tempeh had.
The researchers also found that the soybean tempeh was also primarily effective only within the medium of the intestines. Other studies have shown that the Rhizopus oligosporus yeast can deter Streptococcus cremoris and B. subtilis in laboratory studies, but tempeh has not shown to inhibit E. coli in laboratory research outside of the intestines.
Tempeh shown to cure diarrhea
In the meantime, both human and animal studies have shown tempeh to inhibit diarrhea – which are typically caused by bacteria infections from E. coli, Enterococcus species and others.
A study from the Netherlands’s Wageningen University found that tempeh damages E. coli’s adhesion abilities within the intestines. Adhesion is what allows bacteria to attach to and grow among the tissues.
The researchers found that one of the proteins of the fermented culture of tempeh with the size of 5.5 kDa seems to produce the adhesion-limiting ability. This protein occurs within the culture’s casein hydrolysate.
The bottom line is that soybean tempeh is not just a delicious traditional food. It has a medicinal effect of stimulating probiotics within the gut; it also has an antibacterial effect – making it harder for E. coli to thrive within the intestines.
Soy tempeh is not only delicious, it is a complete protein food – containing all essential aminos – and contains numerous phytonutrients that have been shown to balance hormone levels and reduce cardiovascular disease. The fermenting process also reduces phytates – a frequent complaint about soy. (Phytates are also reduced in the gut by probiotics.)
Kuligowski M, Jasińska-Kuligowska I, Nowak J. Evaluation of bean and soy tempeh influence on intestinal bacteria and estimation of antibacterial properties of bean tempeh. Pol J Microbiol. 2013;62(2):189-94.
Roubos-van den Hil PJ, Schols HA, Nout MJ, Zwietering MH, Gruppen H. First characterization of bioactive components in soybean tempe that protect human and animal intestinal cells against enterotoxigenic Escherichia coli (ETEC) infection. J Agric Food Chem. 2010 Jul 14;58(13):7649-56. doi: 10.1021/jf101379y.
Roubos-van den Hil PJ, Nout MJ, van der Meulen J, Gruppen H. Bioactivity of tempe by inhibiting adhesion of ETEC to intestinal cells, as influenced by fermentation substrates and starter pure cultures. Food Microbiol. 2010 Aug;27(5):638-44. doi:10.1016/j.fm.2010.02.008.
Roubos-van den Hil PJ, Dalmas E, Nout MJ, Abee T. Soya bean tempe extracts show antibacterial activity against Bacillus cereus cells and spores. J Appl Microbiol. 2010 Jul;109(1):137-45. doi: 10.1111/j.1365-2672.2009.04637.x.