Schopnost bakterií využívat syntetická sladila a cukerné alkoholy jako zdroj energie

Bc. Tereza Procházková

Master's thesis

The ability of bacteria to utilize artificial sweeteners and sugar alcohols as a sole energy source

Abstract:

Vliv syntetických sladidel a cukerných alkoholů na složení mikrobiomu, je stále více diskutovaným tématem, pro které dosud neexistuje dostatek průkazných vědeckých závěrů. Cílem této diplomové práce bylo testování schopnosti bakterií, které jsou přirozenou součástí trávicího traktu, metabolizovat vybraná umělá sladidla a cukerné alkoholy jako zdroj energie. Celkem bylo otestováno 32 bakterií kmenů Firmicutes, Bacteroidetes, Proteobacteria a Actinobacteria, jež se největší měrou podílí na složení mikrobiomu. Celkem bylo testováno 8 substrátů, 4 syntetická sladidla a 4 cukerné alkoholy. Experiment byl prováděn v in vitro podmínkách, za použití API médií, obohacených o jeden z testovaných substrátů, který sloužil jako jediný zdroj energie. Jako pozitivní kontrola bylo použito médium s glukózou a jako negativní kontrola sloužilo samostatné médium. Glukóza i jednotlivá sladidla byla do API médií aplikována ve stejné koncentraci, tedy 1,5 g/l. Vyhodnocení experimentu probíhalo vizuálně, na základě změny optické denzity a barvy média. Ke zjištění intenzity nárůstu bakterií, byla využita McFarlandova stupnice. Ze získaných výsledků vyplývá, že všechna syntetická sladidla a cukerné alkoholy selektivně podporují růst pouze některých bakterií. Testované substráty významně podporovaly růst bakterií rodu Lactobacillus, Bacteroides, Bifidobacterium, Clostridium a také bakterie E. faecium. Syntetická sladidla podporovala růst především bakterií kmene Firmicutes, Bacteroidetes a Actinobacteria. Sorbitol podporoval růst i bakterií kmene Proteobacteria. V případě bakterií B. bifidum, E. coli a S. enterica byla zjištěna kmenová specifita ve schopnosti využívat dané substráty k růstu. Zjištěný nárůst probiotických bakterií naznačuje, že syntetická sladidla a cukerné alkoholy mohou mít prebiotické účinky. Na druhou stranu se také mohou podílet na vzniku či postupu zubních kazů. Z tohoto pohledu může být působení syntetických sladidel a cukerných alkoholů srovnatelné s účinky fermentovatelných sacharidů. Taktéž bylo zjištěno, že při utilizaci substrátů, zejména bakteriemi rodu Lactobacillus a Bifidobacterium, dochází buď ke tvorbě metabolitů v jiném poměru či ke tvorbě zcela jiných, než v případě glukózy. Ze získaných výsledků vyplývá, že syntetická sladidla a cukerné alkoholy mohou podporovat růst probiotických i patogenních mikroorganismů a ve vztahu k zubním kazům mohou mít kariogenní účinky.

Abstract:

Effects of synthetic sweeteners and sugar alcohols on gut microbiota composition is an increasingly discussed topic for which there are not yet enough conclusive scientific conclusions. This diploma thesis aimed to test the ability of bacteria naturally inhabiting digestive tract to metabolize selected artificial sweeteners and sugar alcohols as the sole energy source. A total of 32 bacteria of Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria phyla, which are dominant constituents of gut microbiome, were used for the test. A total of 8 substrates, 4 synthetic sweeteners and 4 sugar alcohols were tested. The experiment was performed in vitro, using API media enriched with one of the tested substrates. Medium with glucose was used as a positive control and medium without added substrate was used as a negative control. All the substrates including glucose were applied into API media in the same concentration 1.5 g/l. The evaluation of the experiment was performed visually, based on changes in optical density and media color. The McFarland scale was used to determine the intensity of the bacteria growth. The results showed that all synthetic sweeteners and sugar alcohols selectively support the growth only of some bacteria. The tested substrates significantly promoted the growth of Lactobacillus, Bacteroides, Bifidobacterium, Clostridium, and also E. faecium. Synthetic sweeteners promoted the growth mainly of Firmicutes, Bacteroidetes, and Actinobacteria. Sorbitol also supported the growth of Proteobacteria. In the case of B. bifidum, E. coli, and S. enterica, the ability to metabolize given substrates was found to be strain specific. Result also suggested that synthetic sweeteners and sugar alcohols may have prebiotic effects. On the other hand, they can also contribute to the development or progression of tooth decay, thus their effects could be considered comparable to carbohydrates. It was also found that Lactobacillus and Bifidobacterium species produced from these substrates either metabolites in a different ratio or chemical substances other than from glucose. The obtained results showed that synthetic sweeteners and sugar alcohols can support the growth of both, probiotic and pathogenic microorganisms and they can have cariogenic effects concerning tooth decay.Effects of synthetic sweeteners and sugar alcohols on gut microbiota composition is an increasingly discussed topic for which there are not yet enough conclusive scientific conclusions. This diploma thesis aimed to test the ability of bacteria naturally inhabiting digestive tract to metabolize selected artificial sweeteners and sugar alcohols as the sole energy source. A total of 32 bacteria of Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria phyla, which are dominant constituents of gut microbiome, were used for the test. A total of 8 substrates, 4 synthetic sweeteners and 4 sugar alcohols were tested. The experiment was performed in vitro, using API media enriched with one of the tested substrates. Medium with glucose was used as a positive control and medium without added substrate was used as a negative control. All the substrates including glucose were applied into API media in the same concentration 1.5 g/l. The evaluation of the experiment was performed visually, based on changes in optical density and media color. The McFarland scale was used to determine the intensity of the bacteria growth. The results showed that all synthetic sweeteners and sugar alcohols selectively support the growth only of some bacteria. The tested substrates significantly promoted the growth of Lactobacillus, Bacteroides, Bifidobacterium, Clostridium, and also E. faecium. Synthetic sweeteners promoted the growth mainly of Firmicutes, Bacteroidetes, and Actinobacteria. Sorbitol also supported the growth of Proteobacteria. In the case of B. bifidum, E. coli, and S. enterica, the ability to metabolize given substrates was found to be strain specific. Result als

Abstract:

o suggested that synthetic sweeteners and sugar alcohols may have prebiotic effects. On the other hand, they can also contribute to the development or progression of tooth decay, thus their effects could be considered comparable to carbohydrates. It was also found that Lactobacillus and Bifidobacterium species produced from these substrates either metabolites in a different ratio or chemical substances other than from glucose. The obtained results showed that synthetic sweeteners and sugar alcohols can support the growth of both, probiotic and pathogenic microorganisms and they can have cariogenic effects concerning tooth decay.

Keywords

Syntetická sladidla, cukerné alkoholy, zubní kaz, organické kyseliny, intestinální mikrobiota

Keywords

Artificial sweeteners, sugar polyols, intestinal microbiome, dental carries, organic acids

Language used: Czech

Date on which the thesis was submitted / produced: 25. 4. 2021

Thesis defence

• Supervisor: Ing. Hana Šubrtová Salmonová, Ph.D.

Czech University of Life Sciences Prague

Faculty of Agrobiology, Food and Natural Resources

Master programme:
Food and Nutrition