Oligosaccharides are bioactive carbohydrates that have properties beyond their content of calories; however, structure and degree of polymerisation were believed to play a major role in such bioactivity in particular the ones with degree of polymerisation 2-10. Oligosaccharides of specific degree of polymerisation were prepared by hydrolysis of arabinan using a commercial mixed glycanase preparation (VISCOZYME™ L) in a membrane reactor. A lab scale ultrafiltration unit was operated at a pressure of 1 bar, a stirrer speed of 250 rpm and a working volume of 200 ml. The temperature was controlled at 35°C and pH at 4.5. Enzymatic hydrolysis of arabinan produced oligosaccharides with a wide range of degree of polymerisation values but favoured degree of polymerization > 10. In batch reaction arabinan concentration 5% WV-1 was higher in terms of quantities of oligosaccharides than 2.5% though the production delayed (5 h vs. 3 h for 5% and 2.5% respectively). Oligosaccharides of degree of polymerisation 2-10 were produced after 2 hrs of reaction time when arabinan concentration was 5% WV-1 using fed-batch hydrolysis. Diafiltration using buffer as substitute for hydrolysate has failed to produce similar results in comparison to fed-batch. Small amount of AOS of dp 2-10 were produced only at 3 h. We showed that production of arabino-oligosaccharides with specific degree of polymerisation was achievable within short time (2 h). Overall results suggested that hydrolysis of arabinan in a controlled reactor to produce short chain AOS was mainly affected by; substrate concentration and time of reaction.