Hydrogen production by hup− mutant and wild-type strains of Rhodobacter capsulatus from dark fermentation effluent of sugar beet thick juice in batch and continuous photobioreactors

Abstract

Photofermentative production of hydrogen is a promising and sustainable process; however, it should be coupled to dark fermentation to become cost effective. In order to integrate dark fermentation and photofermentation, the suitability of dark fermenter effluents for the photofermentative hydrogen production must be demonstrated. In this study, thermophilic dark fermenter effluent (DFE) of sugar beet thick juice was used as a substrate in photofermentation process to compare wild-type and uptake hydrogenase-deficient (hup (-)) mutant strains of Rhodobacter capsulatus by means of hydrogen production and biomass growth. The tests were conducted in small-scale (50 mL) batch and large-scale (4 L) continuous photobioreactors in indoor conditions under continuous illumination. In small scale batch conditions, maximum cell concentrations were 0.92 gdcw/L c and 1.50 gdcw/L c, hydrogen yields were 34 % and 31 %, hydrogen productivities were 0.49 mmol/(L c·h) and 0.26 mmol/(Lc·h), for hup (-) and wild-type cells, respectively. In large-scale continuous conditions, maximum cell concentrations were 1.44 gdcw/L c and 1.87 gdcw/L c, hydrogen yields were 48 and 46 %, and hydrogen productivities were 1.01 mmol/(L c·h) and 1.05 mmol/(L c·h), for hup (-) and wild-type cells, respectively. Our results showed that Rhodobacter capsulatus hup (-) cells reached to a lower maximum cell concentration but their hydrogen yield and productivity were in the same range or superior compared to the wild-type cells in both batch and continuous operating modes. The maximum biomass concentration, yield and productivity of hydrogen were higher in continuous mode compared to the batch mode with both bacterial strains.

Reliable determination of the growth and hydrogen production parameters of the photosynthetic bacterium Rhodobacter capsulatus in fed batch culture using a combination of the Gompertz function and the Luedeking-Piret model

“…Since the first study [ 44 ] devoted to the outdoor H 2 production during a fed-batch culture of Rhodopseudomonas sphaeroïdes, many studies with PNS (purple-non-sulfur) bacteria have been carried out in different culture modes including fed-batch, repeated conditions or semi and continuous condition. They were summarized by Argun and Kargi [ 20 ], Androga et al [ 41 ], Sagnak and Kargi [ 42 ], Basak et al [ 10 ], and Uyar et al [ 43 ]. Table 4 incorporates these and more recent data based on fed-batch and semi-continuous H 2 production processes using either pure PNS cultures or co-cultures with dark fermentative bacteria.…”

“…[ 16 ], and Uyar et al. [ 43 ]. Strains Carbon and nitrogen sources Photobioreactor characteristics and operating conditions Fed batch, semi continuous conditions Maximal H 2 productivity a (mM H 2 L −1 medium h −1 ) Substrate conversion efficiency (mol H 2 mol −1 carbon source) Ref.…”

“…H 2 -producing processes based on fed-batch regime. These processes have been previously summarized by Argun and Kargi 20], Androga et al [41], Sagnak and Kargi [42], Basak et al [16], and Uyar et al [43]. illumination increased the difficulty to compare experimental conditions.…”

Evaluation of the Two-Stage Fermentative Hydrogen Production from Sugar Beet Molasses

“…Judging from the results of the sensitivity analysis presented in Section 3.2, an increase in hydrogen productivity in photofermentation deserves special attention because in relation to its assumed value of 0.5 mmol/L/h, the margin of potential improvement is much wider than 20% assumed in the analysis. Productivity of 0.67 mmol/L/h (34% higher) has been achieved in the investigation of molasses processing [23], while productivity of 1.05 mmol/L/h has been reported from the research of hydrogen production from sugar beet thick juice, a feedstock similar to molasses [24]. Moreover, estimates of attainable productivity as high as 3.3 mmol/L/h have been mentioned in the literature [39].…”

“…The two-step process concept considered in this paper is based on the results of research project HYVOLUTION [9]. Contributions from follow-up studies are also taken into account [12,23,24]. The design studies performed as part of the HYVOLUTION work programme included analyses of two plant concepts: A stand-alone plant relying on feedstock supply from outside [25] and an add-on plant energy-integrated with the feedstock source exemplified by a beet-sugar factory [26].…”