Microorganisms in Whole Botanical Fermented Foods Survive Processing and Simulated Digestion to Affect Gut Microbiota Composition

Abstract

Botanical fermented foods have been shown to improve human health, based on the activity of potentially beneficial lactic acid bacteria (LAB) and yeasts and their metabolic outputs. However, few studies have explored the effects of prolonged storage and functional spices on microbial viability of whole fermented foods from fermentation to digestion. Even fewer have assessed their impact on the gut microbiota. Our study investigated the effects of production processes on LAB and yeast microbial viability and gut microbiota composition. We achieved this by using physicochemical assessments and an in vitro gastrointestinal and a porcine gut microbiota model. In low-salt sauerkraut, we assessed the effects of salt concentration, starter cultures, and prolonged storage, and in tibicos, prolonged storage and the addition of spices cayenne, ginger, and turmeric. In both food matrices, LAB counts significantly increased (p<0.05), reaching a peak of 7-8 log cfu/g, declining to 6-6.5 log cfu/g by day 96. Yeast viability remained at 5-6 log cfu/g in tibicos. Ginger tibicos had significantly increased LAB and yeast viability during fermentation and storage (p<0.05). For maximum microbial consumption, tibicos should be consumed within 28days, and sauerkraut, 7weeks. Simulated upper GI digestion of both products resulted in high microbial survival rates of 70-80%. The 82% microbial survival rate of cayenne tibicos was significantly higher than other treatments (p<0.05). 16S rRNA sequencing of simulated porcine colonic microbiota showed that both spontaneously fermented sauerkraut and tibicos increase the relative abundance of Megasphaera 85-fold. These findings will inform researchers, producers, and consumers about the factors that affect the microbial content of fermented foods, and their potential effects on the gut.

Keywords: fermented food; gut microbiota; in vitro digestion; lactic acid bacteria; sauerkraut; tibicos; water kefir; yeasts.

Figure 1

Lactic acid bacteria (LAB) counts in sauerkraut remain sufficiently high during storage. Changes in LAB count during fermentation (20–25°C for 7days) and storage (4°C for a further 88days) of three sauerkraut treatments. () spontaneous fermentation with 0.6% salt; () spontaneous fermentation with 1.5% salt; () inoculated fermentation with 0.91% (w/w) starter cultures and 0.6% salt. Sampled on days 0, 1, 3, and 7 (during fermentation), and on days 13, 19, 34, 47, and 95. The timeline of fermentation and storage is separated by the vertical blue line. The results were expressed as mean standard deviation (n=3) for each treatment group.

Figure 2

Lactic acid bacteria (LAB) and yeast counts in tibicos increase during storage and are significantly higher when ginger is added. Changes in viable LAB (A) and yeast (B) counts in four tibicos treatments during fermentation (20–25°C for 3days with tibicos; and with three different additives added on day 3 for 2days of secondary fermentation without tibicos and storage at 4°C for a further 86days). () Plain tibicos; () tibicos with 0.5% (w/v) organic ginger powder; () tibicos with 0.125% (w/v) organic cayenne powder; () tibicos with 0.25% (w/v) organic turmeric powder. Sampled daily during fermentation and on days 12, 19, 33, 47, and 96. The timeline of fermentation with the tibicos grains and separation to enter storage is indicated by the vertical blue line. The results were expressed as mean standard deviation (n=3) for each treatment group.

Figure 3

Lactic acid bacteria in sauerkraut survive simulated oral, gastric, and small intestinal conditions. () Total LAB plate counts before in vitro digestion; () total LAB plate counts after simulated GI conditions. The results were expressed as mean standard deviation (n=3) for each treatment group. Means with the same letter are not significantly different (p<0.05).

Figure 4

Lactic acid bacteria (LAB) and yeasts in tibicos survive simulated oral, gastric, and small intestinal conditions. LAB (A) and yeast (B) counts. () LAB or yeast counts before in vitro digestion; () LAB or yeast counts after simulated GI conditions. The results were expressed as mean standard deviation (n=3) for each treatment group. Means with the same letter are not significantly different (p<0.05).

Figure 5

Colonic fermentation of digested sauerkraut affects the final gut bacterial profile. Microbial taxa are characterized to the phylum (A); family (B); genus (C) levels. Dominant bacterial taxa are given with greater than 1.0% relative abundance. Blank: fecal slurry with digestive fluids. Control: fecal slurry with digestive fluids post-colonic fermentation. Spon 0.5%: spontaneously fermented sauerkraut with 0.6% salt; Spon 1.5%: spontaneously fermented sauerkraut with 1.5% salt; Inoc 0.6%: inoculated sauerkraut with 0.6% salt; Unferm 1.5%: unfermented cabbage with 1.5% salt.

Figure 6

Colonic fermentation of digested tibicos affects the final gut bacterial profile. Microbial community structures in the four tibicos treatments. Microbial taxa are characterized to the phylum (A); family (B); genus (C) levels. Dominant bacterial taxa are with greater than 1.0% relative abundance. Blank: fecal slurry with digestive fluids. Control: fecal slurry with digestive fluids post-colonic fermentation.