Carob (Ceratonia siliqua L.) as a functional synbiotic matrix: biochemical composition, probiotic compatibility, and gut microbiota modulation in food systems

Disorders of gut-brain interaction (DGBI) are common worldwide, and their frequency has risen alongside the dietary shift that has stripped fermentable fibre out of everyday diets. Carob ( Ceratonia siliqua L. ) is a Mediterranean agro-industrial by-product that has mostly been put to low-value uses, although its composition is unusually varied for a fibre source. This review sets out what is known about that composition, covering galactomannans, polyphenols, dietary fibre and pinitol, and then examines how carob behaves during food processing. Three synbiotic roles are considered. Carob is a fermentable substrate that favours Lactobacillus , Bifidobacterium and the production of short-chain fatty acids (SCFA). It carries polyphenols that act on microbial niches alongside the fibre fraction. It is also technologically compatible with fermented matrices, where it helps probiotic cells stay viable. Mechanistic work and in vitro fermentation converge on the same picture: carob belongs among differentiated prebiotic ingredients, not among substitutes for inulin, galacto-oligosaccharides (GOS) or β-glucans. Four problems still block clinical validation. The materials tested differ widely between fractions and geographical origins; in vitro fermentation models remain distant from human physiology; almost no clinical trial has been designed around carob; and strain-substrate compatibility has never been demonstrated rigorously. The review closes with a research agenda covering targeted randomised controlled trials, CAZy-based genomic screening of candidate probiotic strains, stratified precision-nutrition designs and standardised formulations.