Improvement of fermentative biohydrogen production by Clostridium butyricum CWBI1009 in sequenced-batch, horizontal fixed bed and biodisc-like anaerobic reactors with biomass retention

Abstract

A horizontal tubular fixed bed bioreactor (HFBR) and an anaerobic biodisc-like reactor (AnBDR) were designed to both fix Clostridium biomass and enable rapid transfer of the hydrogen produced to gas phase in order to decrease the strong effect of H 2 partial pressure and H 2 supersaturation on the performances of Clostridium strains. The highest H 2 production rate (703 mL H 2 /L.h) and yield (302 mL/g glucose consumed i.e. 2.4 mol/mol) with the pure culture were recorded in the AnBDR with 300 mL culture medium (total volume 2.3 L) at pH 5.2 and a glucose loading rate of 2.87 g/L.h. These results are about 2.3 and 1.3-fold higher than those achieved in the same bioreactor with 500 mL liquid medium and with the same glucose consumption rate. Therefore, our experimentations and a short review of the literature reported in this paper emphasize the relevance of performing bioreactors with high L/G transfer.Keywords: Clostridium; hydrogen production; biofilm; bioreactor; pure strain CWBI -ULg 2/35 IntroductionThe fermentative production of hydrogen has drawn increased attention in recent years. This biological process called "dark fermentation" (DF) offers new opportunities to produce "green" energy from various renewable resources and organic wastes [1][2][3]. While significant improvements have been made in development of such alternative H 2 production systems, more technical progress and cost reduction needs to occur for them to compete with current large scale technologies e.g. methane-reforming process. By contrast, for local and smaller scale DF and some other opportunities, biohydrogen production processes would be cost competitive since the feedstocks are available almost anywhere and crucial interest is paid for both energy independence and efficient utilization [4,5]. However, optimization is still needed for DF regarding the bioreactor design, rapid removal and purification of gases, use of cheaper feedstock, genetic and molecular engineering to redirect metabolic pathway [6][7][8][9][10].Moreover, DF is only likely to be viable as an industrial process if integrated with a process that maximizes energy recovery from the fermentation end-products. The traditional methaneproducing anaerobic digestion process is the most promising since about 10 to 30 % more energy could be generated in the two-stage integrated system comparing to a single stage methanogenic process [11]. Besides, very prospective processes to convert acetate from DF spent medium exist such as further biohydrogen production (towards the maximum theoretical yield of 12 mol/mol glucose) by photosynthetic non-sulfur bacteria or direct electricity production in microbial fuel cells [6,11].In the past decades, most studies on biohydrogen production processes dealt with suspended culture systems such as the conventional (dis-)continuous stirred tank reactors (CSTR) since they are relatively simple and easy to operate. These investigations, several times reviewed [5,10,12,13], enabled to optimize number of operating parameters such as the ...

Investigation of the links between mass transfer conditions, dissolved hydrogen concentration and biohydrogen production by the pure strain Clostridium butyricum CWBI1009

“…Authors also combined both effects by sparging gases directly in the media, therefore affecting simultaneously the hydrodynamic behaviour and hydrogen partial pressure in the bioreactor [16,17,29,50,51]. Finally, new bioreactors have been proposed with original design or specific carriers that improved liquid distribution and the specific transfer area [44,47,52,53].…”

“…In the sequences without pH control the lag time was shorter than with pH control since higher initial pH favours bacterial growth instead of biohydrogen production [34]. Maximum HPR increases with stirring speed (in RPM) according to a [44]. In addition to the exchange surface area that also affected H 2 yields in BHP tests, these three parameters (exchange surface area, stirring speed and gas stripping) that are involved in H was measured due to low H 2 partial pressure achieved by constant degassing with N 2 .…”

Effect of the nitrogen source on the hydrogen production metabolism and hydrogenases of Clostridium butyricum CWBI1009

“…The Clostridium butyricum CWBI1009 strain was selected for the study due to its high hydrogen production activity while fermenting different carbon sources (glucose, disaccharides or starch) [14][15][16]. Moreover, the strain achieved very high performance (up to 3.4 mol H /mol glucose) in immobilised cultures [17].…”