Towards the integration of dark- and photo-fermentative waste treatment. 3. Potato as substrate for sequential dark fermentation and light-driven H 2 production

Abstract

The goal of the study was to characterize H 2 production in an integrated process utilizing potato homogenate (PH) for dark, fermentative H 2 production followed by H 2 photoproduction using purple non-sulfur bacteria. Emphasis was placed on (a) examining potato fermentation effluent (FE) as substrate for H 2 photoproduction, (b) estimating the yield and efficiency of both processes, and (c) elucidating the physiological factors influencing the integrated system as a whole. In the dark stage maximal production of gas (11.5 L L −1 of the culture) and VFA (350 mM) were observed with a PH concentration of 400 g L −1 of medium, but higher yields (0.05 L g −1 PH; 1.9 mmol g −1 PH) were obtained at PH concentrations of 50–100 g L −1. H 2 photoproduction by purple bacteria was inhibited at high FE content. Upon suitable dilution, adequate illumination, and supplementation with Fe/Mg/phosphate nutrients, H 2 photoproduction reached 40 L L −1 of non-diluted FE, with a total H 2 yield of 5.6 mol mol −1 glucose equivalent for the two-stage integrated process.