Abstract
Particle size is regarded as an important characteristic of plant-based foods in terms of digestion and fermentation. However, it is unclear to what extent the physico-chemical characteristics of different particle sizes affect microbial composition and functionality. In this study, two different particle sizes for sorghum, wheat grain, oat bran, apple, and carrot were fermented in vitro. Following fermentation, DNA was extracted and underwent 16S gene sequencing, followed by the profiling of microbial composition and predicted functions. Associations were analysed between particle size, water-holding capacity (WHC), pectin content, microbial composition and function, and in vitro gas kinetics and fermentation end-products. WHC was driven by the presence and content of pectin, and was strongly associated with both the microbial composition, and fermentation outcomes. For example, of 39 genera with a relative abundance >0.5%, the abundance of 25 genera were significantly (P < 0.05) correlated to WHC across all samples. Within the low pectin content cereal samples, when these were analysed independently of the apple and carrot samples, WHC was also associated with fermentation outcomes. For cereal and apple samples, size reduction did not lead to obvious microbial composition and functional profile changes, possibly due to the general microbial capability to degrade starch present in cereal and comparable pectin contents in apple for different sizes. However, for different sizes of carrot, the microbial composition and functional profile alterations were related to the pectin contents. Overall, the physico-chemical characteristics, such as WHC, and both pectin and starch content are related to composition and functional profiles of human faecal microbiota following in vitro fermentation.
Published Version
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