Prebiotic effect of mucilage (MO) and pectic-derived (PO) oligosaccharides from prickly pear cactus stems was assessed on both cultures and metabolic activity of microbial communities from the human colon. The MO treatment enhanced lactobacilli growth up to 23.8%, while PO increased the bifidobacteria population by 25%. Furthermore, the addition of MO produced a slight decrease in enterococci, enterobacteria, staphylococci, and clostridia of about 4%. Increased levels of the short-chain fatty acids (SCFA) were attained in the cultures at rates of 35 and 16% in response to MO and PO treatments, respectively. Propionic acid (propionate) and butanoic acid (butyrate) production increased at least 50% throughout MO and PO treatments. A decrease in the ammonium level of 11.5% was produced by MO treatment. This research indicates that a mixture of MO and PO oligosaccharides from nopal (Opuntia ficus-indica) could act as prebiotic.