Abstract
As a renewable energy carrier, dark fermentative biohydrogen (H2) represents a promising future alternative to fossil fuels. Recently, the limited H2 yield of 4 moles of H2 per mole glucose, the so-called “Thauer limit”, was surpassed by a defined artificial consortium. In this article, we demonstrate the upscaling of this drawing board design, from serum bottles to laboratory scale bioreactors. Our results illustrate that this designed microbial co-culture can be successfully implemented in batch mode, with maximum H2 yields of 6.18 and 4.45 mol mol−1 substrate. Furthermore, we report volumetric H2 productivities of 105.6 and 80.8 mmol H2 L−1 h−1. These rates are higher than for any other dark fermentative H2 production system using a synthetic microbial co-culture applied in batch mode on a defined medium. Our study is an important step forward for the application of artificial microbial consortia in future biotechnology and energy production systems.
Highlights
Molecular hydrogen (H2 ) is an energy carrier with high combustion yields [1]
The low Y(H2/S) is the major drawback of dark fermentative H2 production (DFHP), which is restricted to a theoretical maximum of 4 moles H2 produced per one mole of glucose consumed in microbial pure cultures and microbial enrichment cultures when acetate is produced as a by-product [5]
Artificial microbial ecosystems can be effectively used for scale-up of DFHP from closed batch to lab scale bioreactors
Summary
Produced H2 , referred to as biohydrogen production (BHP), is considered an environmentally friendly clean alternative with near zero carbon emission and has potential to replace fossil fuels as energy carriers [2]. The H2 evolution rate (HER/mmol H2 L−1 h−1 ) represents the volumetric productivity over time and is independent of the respective culture used, as opposed to the substrate conversion efficiency (Y(H2/S) /mol H2 mol−1 substrate). Taking these units into consideration, the high HER, rapid cell growth, and relatively simple implementation due to non-requirement of light energy, advocate the use of dark fermentative H2 production (DFHP) over photobiological H2 production processes [3,4]. The low Y(H2/S) is the major drawback of DFHP, which is restricted to a theoretical maximum of 4 moles H2 produced per one mole of glucose consumed in microbial pure cultures and microbial enrichment cultures when acetate is produced as a by-product [5]
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