Effect of the consumption of brazzein and monellin, two recombinant sweet-tasting proteins, on rat gut microbiota

Abstract

Sweet-tasting proteins (SPs) are proteins of plant origin initially isolated from tropical fruits. They are thousands of times sweeter than sucrose and most artificial sweeteners. SPs are a class of proteins capable of causing a sweet taste sensation in humans when interacting with the T1R2/T1R3 receptor. SP thaumatin has already been introduced in the food industry in some countries. Other SPs, such as monellin and brazzein, are promising products. An important stage in researching SPs, in addition to confirming the absence of toxicity, mutagenicity, oncogenicity, and allergenic effects, is studying their influence on gut microbiota. In this paper we describe changes in the composition of rat gut microbiota after six months of consuming one of two recombinant SPs-brazzein or monellin. A full length 16S gene sequencing method was used for DNA library barcoding. The MaAsLin2 analysis results showed noticeable fluctuations in the relative abundances of Anaerocella delicata in brazzein-fed rat microbiota, and of Anaerutruncus rubiinfantis in monellin-fed rat microbiota, which, however, did not exceed the standard deviation. The sucrose-fed group was associated with an increase in the relative abundance of Faecalibaculum rodentium, which may contribute to obesity. Overall, prolonged consumption of the sweet proteins brazzein and monellin did not significantly change rat microbiota and did not result in the appearance of opportunistic microbiota. This provides additional evidence for the safety of these potential sweeteners.

Keywords: food additive; intestinal bacteria; microbiome; microbiota composition; natural sweetener; safety; sugar substitute; symbiotic microorganism.

Figure 1

Results of exploratory analysis of gut microbiota changes in experimental groups. (A) Taxonomic distribution at the genus level for each experimental group across time points (weeks). X-axis indicates time points (weeks), while Y-axis shows relative abundance distributions in experimental groups. Different colors correspond to different taxonomic annotations. (B) Changes in Shannon index values for each experimental group across time points. X-axis indicates time points (weeks), Y-axis Shannon index values. Different colors correspond to different experimental groups. (C) Changes in Bray–Curtis dissimilarity calculated from baseline for each experimental group at different time points. X-axis indicates time points (weeks), Y-axis Shannon index values. Different colors correspond to different experimental groups. (D) Non-metric multidimensional scaling (NMDS) visualization of gut microbiome taxonomic profiles and Bray–Curtis dissimilarity metric (stress = 0.22). Different colors indicate different experimental groups. (E) NMDS visualization of (D) stratified by time point variable.

Figure 2

Box plots generated by MaAsLin2 show the differential abundance of microbial species by experimental group. FDR p-values and regression coefficients as well as experimental group variables are shown in the upper right corner of each plot. The analysis was performed with the following parameters: fixed_effects = c(“sex,” “group”), reference = c(c(“group, control”)), random_effects = c(“time_point,” “sourceid”), max_significance = 0.01. The x-axis indicates experimental group, while the y-axis indicates relative abundance. Differently abundant species are indicated by letters: (A) Faecalibaculum rodentum; (B) Anaerotruncus rubiinfantis; (C) Anaerocella delicata.