Bioprocessing technology to exploit organic palm date (Phoenix dactylifera L. cultivar Siwi) fruit as a functional dietary supplement

•Fermentation increased the antioxidant activity of date fruit puree (DP).•Fermentation modified the phenolic profiles of DP.•Fermented DP had increased level of insoluble dietary fibers.•Fermented DP had increased level of GABA and conjugated fatty acids.•Fermented DP modulated positively in vitro gut microbiota and SCFA synthesis. Date fruit (Phoenix dactylifera L.) is a suitable raw matrix for manufacturing of functional ingredients. The aptitude of selected autochthonous lactic acid bacteria for manufacturing of freeze-dried powder from fermented date fruits puree as dietary supplement with health-promoting features was investigated. Fermentation of date fruits puree with selected Lactobacillus plantarum strains allowed the highest concentration of γ-amino butyric acid, conjugated fatty acids, and insoluble dietary fibers. The highest Trolox equivalent antioxidant activity was also induced. Lactic acid fermentation affected the profile of phenolic acids and flavonoids, enriching date fruits puree in phenolic derivatives with high human bioavailability. Fermented date fruits puree was also capable to modulate positively in vitro the growths of several cultivable gut microbial taxa, and enhanced the synthesis of short chain fatty acids. In conclusion, the lactic acid fermentation of date fruits is a suitable tool to achieve a standardized and marketable functional dietary supplement.