Aqueous extracts from date by-products of the sucrose-rich variety "Deglet Nour" were used as a starting substrate to achieve the enzymatic synthesis of fructooligosaccharides (FOS) commonly used as prebiotics. A crude ${eta}$-fructofuranosidase (Ffase) preparation from Aspergillus awamori NBRC4033 was immobilized on chitosan by covalent binding through glutaraldehyde linkages (Yi = 88%, Ya = 54%), and used for this purpose. The effect of water-extraction volume on the FOS synthesis by transfructosylation was studied. It was found that 150 mL/100 g of date by-products gave the best FOS concentration and productivity (123 g/L and 18.5 g/h/100 g respectively), related to an optimal sucrose conversion of 53.26%. The main FOS product was purified via a biogel-P2 gel filtration column. Its structure was determined as 1-kestose: ${alpha}$-D-glucopyranosyl-($1{ ightarrow}2$)-${eta}$-D-fructofuranosyl-($2{ ightarrow}1$)-${eta}$-Dfructofuranoside by combination of $^1H$, $^{13}C$ and 2D-NMR techniques. Our results provide new insights into the enzymatic synthesis of FOS from an alternative source of sucrose, namely date by-products.