This review article focuses on an assessment of the innovative Gas Separation Membrane Bioreactor (GS-MBR), which is an emerging technology because of its potential for in-situ biohydrogen production and separation. The GS-MBR, as a special membrane bioreactor, enriches CO2 directly from the headspace of the anaerobic H-2 fermentation process. CO2 can be fed as a substrate to auxiliary photo-bioreactors to grow microalgae as a promising raw material for biocatalyzed, dark fermentative H-2-evolution. Overall, these features make the GS-MBR worthy of study. To the best of the authors' knowledge, the GS-MBR has not been studied in detail to date; hence, a comprehensive review of this topic will be useful to the scientific community.