The bacterial cultures were able to increase their biomass from the start of the flow experiment until day 4, reaching a ΔOD600 of 0.30 ±0.09 which remained approximately constant until day 6 (Figure ). In comparison to the batch mode, the flow configuration showed an increase in acetate from day 0 to day 6 with a maximum Δ[acetate] of 0.46 ± 0.07 mM (Figure ). The lack of ethanol, lower ΔOD600 and Δ[acetate] can be attributed to the syngas concentration in the photocatalysis gas stream (<0.1%) as well as its formation rate by TiO2|CotpyP compared to the utilized commercial syngas cylinder. As shown in Figure , Cladapt can produce high biomass and C2 product outputs under syngas flow rates as high as 102 µmol CO min -1 and 41 µmol H2 min -1 , highlighting the limitations of the presented photocatalytic system and need to develop improved systems capable of delivering higher syngas formation rates to Cladapt. Our results show that simple photocatalytic powder systems can in principle be used to feed solar syngas to gasfermenting bacteria, thereby providing an alternative to wired devices such as electrolyzers and photoelectrochemical cells . They also serve as a cautionary tale for researchers working in the fields of biohybrids and domino catalysis, emphasizing the need for new renewable energy-driven syngas forming systems and device architectures to fully exploit the capabilities of gas fermenting adapted bacteria, enabling high levels of C2 products and cell growth over time.