Production, Storage Stability, and Susceptibility Testing of Reuterin and Its Impact on the Murine Fecal Microbiome and Volatile Organic Compound Profile.

Christoph Castellani,Sigrid Mayrhofer,Stefan Heinl,Bernhard Kienesberger,Clemens Peterbauer,Georg Singer,Angela Horvath,Hannes Russmayer,Reingard Grabherr,Vanessa Stadlbauer,Beate Obermüller,Ingeborg Klymiuk,Holger Till,Patricia Fuchs,Wolfram Miekisch

doi:10.3389/fmicb.2021.699858

Abstract

Background: Probiotics are generally considered as safe, but infections may rarely occur in vulnerable patients. Alternatives to live microorganisms to manage dysbiosis may be of interest in these patients. Reuterin is a complex component system exhibiting broad spectrum antimicrobial activity and a possible candidate substance in these cases.Methods: Reuterin supernatant was cultured from Lentilactobacillus diolivorans in a bioreactor in a two-step process. Storage stability at −20°C and effect of repeated freeze-thaw cycles were assessed by high performance liquid chromatography (HPLC). Antimicrobial activity was tested against Clostridium difficile, Listeria monocytogenes, Escherichia coli, Enterococcus faecium, Staphylococcus (S.) aureus, Staphylococcus epidermidis, Streptococcus (S.) agalactiae, Propionibacterium acnes, and Pseudomonas aeruginosae. Male BALBc mice were gavage fed with reuterin supernatant (n = 10) or culture medium (n = 10). Fecal volatile organic compounds (VOC) were assessed by gas chromatography mass spectroscopy; the microbiome was examined by 16S rRNA gene sequencing.Results: The supernatant contained 13.4 g/L reuterin (3-hydroxypropionaldehyde; 3-HPA). 3-HPA content remained stable at −20°C for 35 days followed by a slow decrease of its concentration. Repeated freezing/thawing caused a slow 3-HPA decrease. Antimicrobial activity was encountered against S. aureus, S. epidermidis, and S. agalactiae. Microbiome analysis showed no differences in alpha and beta diversity markers. Linear discriminant effect size (LEfSe) analysis identified Lachnospiraceae_bacterium_COE1 and Ruminoclostridium_5_uncultured_Clostridiales_ bacterium (in the reuterin medium group) and Desulfovibrio_uncultured_ bacterium, Candidatus Arthromitus, Ruminococcae_NK4A214_group, and Eubacterium_xylanophilum_group (in the reuterin group) as markers for group differentiation. VOC analysis showed a significant decrease of heptane and increase of 3-methylbutanal in the reuterin group.Conclusion: The supernatant produced in this study contained acceptable amounts of 3-HPA remaining stable for 35 days at −20°C and exhibiting an antimicrobial effect against S. aureus, S. agalactiae, and S. epidermidis. Under in vivo conditions, the reuterin supernatant caused alterations of the fecal microbiome. In the fecal, VOC analysis decreased heptane and increased 3-methylbutanal were encountered. These findings suggest the high potential of the reuterin system to influence the intestinal microbiome in health and disease, which needs to be examined in detail in future projects.

Highlights

The importance of the intestinal microbiome has gained wide scientific interest in health and disease
Under the culture conditions described above a supernatant containing a maximum of 13.4 g/L 3-HPA and 6.8 g/L glycerol could be obtained (Table 1)
Supplement 1 shows an exemplary high performance liquid chromatography (HPLC) curve of the supernatant produced in this study

Summary

Introduction

The importance of the intestinal microbiome has gained wide scientific interest in health and disease. The composition of the intestinal microbiome is susceptible to nutritional changes, medication or chronic diseases such as tumor-associated cachexia, inflammatory bowel disease, or type two diabetes. The modification of the intestinal bacterial composition toward a “healthier” microbiome has become attractive as possible therapeutic or supportive therapy approach. In vulnerable patient cohorts infections with probiotics may occur. Alternatives to live microorganisms to manage dysbiosis are of interest (Redman et al, 2014). In these cases, a helpful alternative in the treatment of intestinal dysbiosis is needed. Probiotics are generally considered as safe, but infections may rarely occur in vulnerable patients. Alternatives to live microorganisms to manage dysbiosis may be of interest in these patients. Reuterin is a complex component system exhibiting broad spectrum antimicrobial activity and a possible candidate substance in these cases

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Discussion

Conclusion