Synbiotics of encapsulated Limosilactobacillus fermentum K73 promotes in vitro favorable gut microbiota shifts and enhances short-chain fatty acid production in fecal samples of children with autism spectrum disorder

Modulation of the gut microbiota has emerged as a promising approach for addressing the gastrointestinal and neurodevelopmental symptoms associated with autism spectrum disorder (ASD). Consequently, this study aimed to evaluate the impact of four formulated synbiotics comprising Limoscilactobacillus fermentum K73, high-oleic palm oil and whey, on the gut microbiota composition of Colombian children with and without ASD. These components were encapsulated through high-shear emulsification and spray drying. The four synbiotics and their individual components were subjected to in vitro digestion and fermentation using samples of Colombian children gut microbiota. Short-chain fatty acids (SCFAs), including lactic, acetic, propionic, and butyric acids, were quantified using HPLC-DAD, while serotonin was determined by an ELISA kit after in vitro fermentations. Changes in microbial structure were assessed by the sequencing of the 16S rRNA gene via next-generation sequencing (NGS). The results revealed a decrease in the abundance of genera like Bacteroides and Dorea in ASD-associated samples after the treatment with the synbiotics. Conversely, an increase in the relative abundance of probiotic-related genera, including Lactobacillus, Streptococcus, and Anaerostipes, was observed. Furthermore, the analysis of SCFAs and serotonin indicated that the synbiotic intervention resulted in an elevated butyric acid and microbial serotonin synthesis, alongside a decrease in propionic acid, which is changes considered beneficial in the context of ASD. This evidence suggests that synbiotics of L. fermentum K73 could represent a promising live biotherapeutic strategy for modulating the gut microbiota of children with ASD.