A review on single stage integrated dark-photo fermentative biohydrogen production: Insight into salient strategies and scopes

In recent times, systematic integration of dark and photofermentation has attracted a lot of attention due to the advantage of enhanced H2 yields and better substrate conversion efficiencies. This integration is done either in a sequential two stage or in a single stage manner, between which the single stage integration (SSI) seems more cost effective. This article thoroughly reviews the salient operational strategies, key factors affecting the H2 yields and overall increment in H2 yields attained in the SSI biohydrogen processes. Selection of more complementing pair of dark and photofermentative microbes, optimization of composition of common growth medium, better strategies for consistent pH control and facilitation of lignocellulosic feedstocks have been identified as major areas requiring in-depth focus and subsequent improvements. Based on the insightful discussions, the current state-of-the-art of SSI bio-H2 technology has been evaluated and its potential to become a reliable hydrogen production technology has been factually assessed.