A flex-matala packed biofilter with specific surface area 365 m(2)/m(3) and free volume 94% was used as a bacteria carrier in a Continuous Stirred Tank Reactor (CSTR) in this study. The continuous stirred tank reactor with packed biofilter (CSTR-PBF) was designed and operated under sugary wastewater substrate at concentration of 20 g total sugar/L and HRT 8-0.5 h to assess the biohydrogen producing ability. Biofilter was installed at 60 mm height from the bottom of bioreactor (middle of the bioreactor). It was found that the optimum condition was at HRT 1 h with HPR of 88.73 L H-2/L/d, substrate utilization of 92.95% and yield of 1.37 mol H-2/mol hexose. A flex packed biofilter used in CSTR system is a better approach to accumulate biomass concentration in bioreactor for enhancing biohydrogen production rate comparison with other kinds of continuous bioreactor. The sugary wastewater used as substrate for biohydrogen production not only produce the renewable energy but also mitigate the organic wastewater pollution. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.