Hydrogen Production From Food Waste in Anaerobic Mesophilic and Thermophilic Acidogenesis

International Journal of Hydrogen Energy 29 (2004) 13551363www.elsevier.com/locate/ijhydene

Hydrogen production from food waste in anaerobic mesophilicand thermophilic acidogenesis

Hang-Sik Shina ;, Jong-Ho Younb, Sang-Hyoun KimaaDepartment of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 373-1, Guseong-dong,

Yuseong-gu, Daejeon, 305-701, South KoreabDepartment of Environmental Information and Engineering, Shinsung College, 49, Duckma-ri, Jungmi-myun, Dangjin-gun,

Chungnam, 343-861, South Korea

Accepted 23 September 2003

Abstract

Hydrogen production from food waste by the mesophilic and thermophilic acidogenic culture acclimated with food wasteat 5 days HRT for the e1ect of pH and volatile solid (VS) concentrations was evaluated. The biogas produced from thethermophilic acidogenic culture was free of methane at all tested pH and VS concentrations, but methane was detected from themesophilic acidogenic culture at all tested pH. The amount of hydrogen production from the thermophilic acidogenic culturewas much higher than that from the mesophilic culture at all tested pH because of the methane free condition and negligiblepropionate production. Increase of VS concentrations from 3 to 10 g VS l1 resulted in the increase of quantity and quality ofhydrogen production. The maximum hydrogen content was 69% (v/v) at 10 g VS l1. The hydrogen yield was in the rangeof 0.91:8 mol-H2=mol-hexose and peaked at 6 g VS l1. Normal butyrate was the main acid product, and the percentagesof butyrate, acetate and propionate at tested VS concentrations were 5460%, 2231% and 0.31%, respectively. Hydrogenproducing microorganisms of Thermoanaerobacterium thermosaccharolytium and Desulfotomaculum geothermicum weredetected from the thermophilic acidogenic culture, while Thermotogales strain and Bacillus species were detected from themesophilic acidogenic culture by PCR-DGGE analysis.? 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

Keywords: Hydrogen; Volatile fatty acids; Food waste; PCR-DGGE; Mesophilic; Thermophilic culture; Thermoanaerobacteriumthermosaccharolytium

1. Introduction

Hydrogen is a promising alternative to fossil fuels dueto its clean and high-energy yield. Anaerobic acidi@cationof organic wastes produces various volatile fatty acids(VFA), H2, CO2 and other intermediates. The reactionsinvolved in hydrogen production are rapid and do not re-quire solar radiation, making them useful for treating largequantities of organic wastes. Not only hydrogen gas itselfis a bene@cial energy source, but also VFA can be used

Corresponding author. Tel.: +82-42-869-3613;fax: +82-42-869-3610.

E-mail address: [email protected] (H.-S. Shin).

either for methane production by methanogenesis or a read-ily biodegradable carbon source for biological nutrients re-moval [13]. Therefore, the harvest of hydrogen at the acid-i@cation stage of anaerobic treatment, leaving the remainingacidi@cation products such as acetate and butyrate for fur-ther methane production or external carbon source for bio-logical nutrients treatment process is a great challenge for itseconomic aspect. Acidi@cation of organic wastes, however,needs hydraulic retention time (HRT) longer than 3 days inwhich hydrogen consumers such as methanogenesis couldbe proliferated. Because of this reason, most researches onhydrogen production have been carried out under inhibitorycondition of hydrogen consumers. In order to inactivate hy-drogen consumers, inocula were cultivated with pure che-micals such as glucose or sucrose at short HRT and/or low

0360-3199/$ 30.00 ? 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.doi:10.1016/j.ijhydene.2003.09.011

1356 H.-S. Shin et al. / International Journal of Hydrogen Energy 29 (2004) 13551363

pH [47], or preheated to harvest spore-forming anaerobicbacteria [6]. Continuous production of hydrogen was alsotried at short HRT to prevent the growth of hydrogen con-sumers [8,9]. However, there have been no studies on con-tinuous hydrogen production at enough HRT from organicsolid wastes. To date, the majority of research has been di-rected at expensive pure substrates or to a much lesser de-gree solid waste or wastewaters, however, for a truly sus-tainable production process and to meet the demand for re-newable energy, more sustainable feed stocks will have to beutilized [10]. Food waste, a carbohydrate-rich organic solidwaste, was used in this study as a substrate for hydrogenproduction. As the generation of food waste amounted to11; 577 tons per day in Korea, which was 25.4% of munici-pal solid waste [11], its management causes much concern.Therefore, the aim of this study was to investigate the

feasibility of hydrogen production from food waste. Themesophilic and thermophilic acidogenic culture, accli-mated with food waste at 5 days HRT which was enoughHRT for acidifying food waste, was used as seed microor-ganisms. This study focused on the ability of hydrogenproduction from the thermophilic acidogenic culture, andthe mesophilic acidogenic culture was also examined forcomparison. The responsible microorganisms for hydro-gen production were examined by denaturing gradient gelelectrophoresis (DGGE) of the polymerase chain reaction(PCR)ampli@ed V3 region of 16S rDNA.

2. Materials and methods

2.1. Feedstock

Food waste collected from a dining hall was ground aftersorting out animal bones and clamshells. It was mixed withdeionized (DI) water (food waste:DI water=1 : 3), and thensieved with a screen (No.4, 4:75 mm ID). Table 1 showsthe characteristics of food waste.

2.2. Seed microorganisms

Two kinds of seed microorganisms, mesophilic and ther-mophilic acidogenic culture, were taken from two identical5 l continuous stirred acidogenic reactors which were oper-ated at 35 1C and 55 1C, respectively. Both reactorswere fed semi-continuously with food waste. The reactorswere operated at 3 g VS l1 day1, 5 days HRT and pH5:6 0:2 for one and half months at steady state. Table 2shows the characteristics of the two seed microorganismsand the average operating parameter values in the mesophilicand thermophilic reactor at steady state.

2.3. Experimental apparatus and procedure

The production of hydrogen and VFA from food wasteby the mesophilic and thermophilic acidogenic culture was

Table 1Characteristics of food waste

Item Unit Value

pH 5.8TS g l1 67.8VS g l1 63.7VS/TS 0.94Total carbohydrate g l1 25.5Carbon, C % TS 51.2Hydrogen, H % TS 7.7Oxygen, O % TS 38.3Nitrogen, N % TS 2.8Sulfur, S % TS 0.7C/N 18.3

studied in 715 ml serum bottles. The mesophilic and ther-mophilic culture taken from each reactor were settled for1 h, and the supernatant was then removed. The settled cul-tures were used as seed microorganisms. The seed microor-ganisms were washed 10 times with the anaerobic mediumto remove VFA. The anaerobic medium of phosphate bu1er,mineral salts and trace metals was made according to Shel-ton and Tiedge [12]. The bottles were @lled with 250 mlof anaerobic medium. Food waste was added as a substratealong with 2:5 g NaHCO3 as a bu1er. The bottles were @lledto the 400 ml mark using nano-pure water. The desired eachinitial pH was adjusted by 2 N KOH and 2 N HCl, and then50 ml of seed microorganisms was added. The desired eachinitial pH was adjusted again after the bottles were @lled tothe 500 ml level using nano-pure water. The bottles wereNushed with N2 and capped tightly before being put on theshaking incubators with 100 rpm at 351C for mesophilicand 551C for thermophilic condition. Control bottles forboth mesophilic and thermophilic were also prepared with-out addition of substrate. To maintain the desired each pHduring the test period, 1:0 ml was taken from the serum bot-tles and the pH was measured using semi-micro pH elec-trode (Corning, USA). The desired each pH was adjustedby adding 2 N KOH or 2 N HCl with a syringe.

2.4. Analyses

The biogas produced was measured using glass syringes,and gas composition was analyzed using a gas chromato-graph (Gow Mac series 580, USA) with a thermal conduc-tivity detector and two columns. The methane and carbondioxide were detected with a column packed with porapakQ (80/100 mesh), and the hydrogen was detected with a col-umn packed with molecular sieve 5A. The temperatures ofinjector, detector and column were kept at 80C, 90C and50C. Helium was used as a carrier gas. VFA was quan-ti@ed by a high-performance liquid chromatography (Spec-trasystem P2000, USA) with an ultraviolet (210 nm) detec-tor and an Aminex HPX-97H (3007:8 mm2) column after

H.-S. Shin et al. / International Journal of Hydrogen Energy 29 (2004) 13551363 1357

Table 2Characteristics of the seed microorganisms and the average operating parameter values from the mesophilic and thermophilic acidogenicreactors at steady state

Seed microorganism Average operating parameters

TSS VSS pH Alkalinity Gas content (%) VFA(mg l1 as COD)(mg l1) (mg l1) (mg l1 as CaCO3)

H2 CH4 TVFA HAc HPr n-HBu

T 6408 6280 5.5 1300 54 0 7800 1200 250 5300M 8725 8470 5.6 1900 3 17 7500 2570 1560 2300

T : Thermophilic acidogenic reactor; M : Mesophilic acidogenic reactor; TVFA : total VFA, HAc: acetate, HPr : propionate, n-HBu:n-butyrate.

pretreatment with 0:45 m membrane @lter. H2SO4 of0:005 M was used as a mobile phase. Carbohydrate wasmeasured using the calorimetric ferric-cyanide method[13]. Measurements of total solid (TS), volatile solid (VS),volatile suspended solid (VSS) and pH were performedaccording to the Standard Methods [14].In order to identify the hydrogen producing microorgan-

isms, DNAs from the mesophilic and thermophilic acido-genic culture were extracted by using the Ultraclean SoilDNA Kit (Cat # 12800-50; Mo Bio Laboratory Inc., USA).The Ultraclean Soil DNA Kit was more e1ective than othermethods such as Phenol/chloroform method etc. for DNAextraction and puri@cation in this study [15]. The 16S rDNAfragments were ampli@ed by PCR. The region correspond-ing to positions 357 and 518 in the 16S rDNA of Escherichiacoli was PCR-ampli@ed using the forward primer EUB357f(5-CCTACGGGAGGCAGCAG-3) with a GC clamp(5-CGCCCGCCGCGCCCCGCGCCCGGCCCGCCGCCCCCG CCCC-3) at the 5 end to stabilize the meltingbehavior of the DNA fragments and the reverse primerUNIV518r (5-ATTACCGCGGCTGCTGG-3). PCR am-pli@cation was conducted in an automated thermal cycler(MWG-Bio TECH, Germany) using the protocol; that is,initial denaturation for 4 min at 94C and 30 cycles ofdenaturation for 40 s at 94C, annealing for 40 s at 55C,extension for 1 min at 72C, followed by a @nal extensionfor 8 min at 72C. PCR mixtures had a @nal volume of50 l which contained 5 l of 10 PCR bu1er, 0:8 mMMgSO4, 0:5 mM of each primer, 0:1 mM dNTP, 25 pgtemplate and 1U polymerase. PCR products were elec-trophoresed on 2% (wt/vol) agarose gel in 1 TAE for30 min for 50 V, and then checked with ethidium bromidestaining to con@rm the amplication. DGGE was carriedout using the Dcode Universal Mutation Detection System(BioRad, USA) in accordance with the manufacturers in-structions. PCR products were electrophoresed in 1 TAEbu1er for 480 min at 70 V and 60C on polyacrylamide gel(7.5%) containing a linear gradient ranging from 40% to60% denaturant. After electrophoresis, polyacrylamide gelwas stained with ethidium bromide for 30 min, and thenvisualized on UV transilluminator. Most of the bands were

excised from DGGE polyacrylamide gel for 16S rDNA se-quencing. DNA fragments from the bands excised were pu-ri@ed using a QIAEX IIGel Extraction Kit (Qiagen, USA),and then PCR-ampli@ed with the forward primer EUB357fwithout a GC clamp and the reverse primer UNIV518r.After PCR ampli@cation, PCR products were puri@ed us-ing MultiScreen Vacuum Manifold (MILLIPORE com.,USA). All the strands of the puri@ed PCR products weresequenced with primers EUB357f by ABI PRISM Big Ter-minator Cycle Sequencing Kit (Applied Biosystems, USA)in accordance with the manufacturers instructions. Searchof the GenBank database was conducted using the BLASTprogram [16].

3. Results and discussion

3.1. E9ect of pH on hydrogen production

The @rst set of batch experiments was performed at2 g VS l1 and pH 4.5, 5.5 and 6.5 for the mesophilicand thermophilic acidogenic culture. During the tests, eachpH could be adjusted in the range of 4.14.5, 5.35.5 and6.36.8 for the mesophilic test, and 4.24.6, 5.55.8 and6.46.8 for the thermophilic test by adding 2 N KOH or2 N HCl with a syringe. Fig. 1 shows the cumulative hy-drogen production from the mesophilic and thermophilicacidogenic culture at tested pH.The cumulative hydrogen production data were @tted to

the modi@ed Gompertz equation [6] by using the @t curvefunction in Sigma Plot 2001 version. All of the correlationcoeVcients, R2, were greater than 0.97 indicating the per-fect @t to the experimental data. The longer lag-phase of thethermophilic test than that of the mesophilic test could beexplained by the fact that the thermophilic and mesophilicseed microorganisms were exposed to a room temperature( 20C) during the setting time of the tests, thus the ac-tivity of the thermophilic seed microorganism was more af-fected by the low temperature than the mesophilic seed mi-croorganism. Since the mesophilic and thermophilic seedmicroorganims were taken from the reactors which were


Incubation time (hours)0 20 40 60 80 100 120 140 160

Cum

ulat

ive h

ydro

gen

prod

uctio

n (m

L)

0

10

20

30

40

50Thermo. pH 4.5Thermo. pH 5.5Thermo. pH 6.5Meso. pH 4.5Meso. pH 5.5Meso. pH 6.5

Fig. 1. E1ect of pH on hydrogen production from the mesophilic and thermophilic acidogenic culture.

operated at pH 5:6 0:2, the lag-phase times of pH 4.5and 6.5 from both mesophilic and thermophilic culture werelonger than the corresponding values of pH 5.5. Table 3illustrates the distribution of key VFA, cumulative hydrogenproduction and headspace gas content with incubation timeat pH 5.5 from the mesophilic and thermophilic acidogenicculture. Table 4 shows the results from the mesophilic andthermophilic culture at pH 4.5, 5.5 and 6.5.From the thermophilic test, butyrate was the main acid

product, while propionate was negligible. The shift of pHfrom 4.5 to 6.5 resulted in the decrease of butyrate and hy-drogen content, while acetate and carbon dioxide gas contentwere increased. No methane was detected through out thetest period at all tested pH. In the case of the mesophilic test,propionate was one of the major acid products and increasedas pH increased. Methane was detected from the incubationtime of 15, 20 and 50 h at pH 6.5, 5.5 and 4.5, respectively,which almost coincided with the incubation time of max-imum cumulative hydrogen production of each test. Totalhydrogen production from the thermophilic test was greaterthan that from the mesophilic test. The hydrogen produc-tion reached the maximum at pH 4.5, but the lag-phase timewas the longest among the tested pH for both mesophilicand thermophilic tests. The yield of hydrogen from the ther-mophilic test was much higher than that from the mesophilictest, and reached the maximum of 0:9 mol-H2=mol-hexoseat pH 4.5. This result was di1erent from the reported op-timum pH for glucose [4], and high-strength rice winerywastewater fermentation [9].Hydrogen gas could be produced if surplus electrons form

in the reaction, and then reduce protons by hydrogenase.The formation of acetate and butyrate accompanies reduc-ing power, whereas the formation of lactate, propionate con-sumed reducing equivalents [17]. It was also reported that

molecular hydrogen was produced during the production ofacetate and butyrate, while hydrogen wass consumed dur-ing the production of propionate [5,18]. Therefore, lowerhydrogen production from the mesophilic test than the ther-mophilic test might be related with the higher productionof propionate that consumed hydrogen, and methanogenesiswhich converted hydrogen to methane.

3.2. E9ect of VS concentrations on hydrogen production

The second set of batch experiments was performed at3, 6, 8 and 10 g VS l1 with the thermophilic acidogenicculture at pH 5.5. The pH 5.5 was thought to be better toevaluate hydrogen production on VS concentions because itcould reduce lag-phase time and be less inNuenced by highVS concentration than pH 4.5. The pH could be adjusted at5:6 0:2 during the test period. Fig. 2 shows the cumula-tive hydrogen production at each VS concentration from thethermophilic acidogenic culture at pH 5.5.All the correlation coeVcients, R2, were greater than 0.98.

Table 5 shows the analysis from the thermophilic acidogenicculture at tested VS concentrations.The hydrogen production and content were increased

as VS concentration increased, and the maximum hydro-gen content of 69% occurred at 10 g VS l1. The biogaswas free of methane at all tested VS concentrations, andthe concentrations of butyrate, acetate and propionatewere 5460 2231%, and 0.31% (c/c), respectively.The speci@c hydrogen production potentials were from46.1 to 91:5 ml g VS1, and reached the maximum of91:5 ml g VS1 at 6 g VS l1. The speci@c hydrogen pro-duction rates ranged from 12 to 19 ml g VS S1 h1, andthe maximum appeared at 10 g VS l1. The speci@c hy-drogen production potentials were similar to the @ndings


Table 3Analysis from the mesophilic and thermophilic acidogenic culture at pH 5.5

Time Thermophilic acidogenic culture Mesophilic acidogenic culture(h)

HAc HPr n-Hbu Cumulative Headspace HAc HPr n-Hbu Cumulative Headspace(mg l1) (mg l1) (mg l1) H2 (ml) gas content (%) (mg l1) (mg l1) (mg l1) H2 (ml) gas content (%)

H2 CO2 N2 CH4 H2 CO2 N2 CH4

10 0 0 51 0 0 38 62 0 164 130 268 2 1 53 46 030 116 1 365 21 15 49 36 0 224 265 299 2.5 0 59 39 254 103 8 593 30 15 60 25 0 286 305 294 2.5 0 60 37 385 95 12 793 38 17 58 25 0 343 319 278 2.5 0 60 35 5134 137 0 898 43 21 57 22 0 408 365 294 2.5 0 60 34 6

Table 4Analysis from the mesophilic and thermophilic acidogenic culture at tested pH

pH H2 H2 H2 yield SHPP SHPR Lag-phase VFA (mg l1 as COD)(ml) (%) (mol-H2/ (ml H2 gVS1) ml H2 g VS S1 h1) time (h)

mol-hexose) TVFA HAc HPr n-HBu

4.5 46.3 23 0.9 46.3 3.0 23.0 994 65 0 925T 5.5 40.1 21 0.8 40.1 2.9 11.7 1120 137 0 898

6.5 28.4 14 0.6 28.4 2.5 14.9 992 254 0 651

4.5 5.0 4 0.1 5.0 0.4 3.6 1152 185 141 628M 5.5 2.5 1 0.05 2.5 0.7 0.5 1337 408 365 294

6.5 1.3 0.5 0.03 1.3 0.3 0.1 1286 524 460 177

T : Thermophilic acidogenic culture; M: Meosphilic acidogenic culture; SHPP : Speci@c hydrogen production potential; SHPR : Speici@chydrogen production rate.

Time (hours)0 50 100 150 200 250 300

Cum

ulat

ive h

ydro

gen

prod

uctio

n (m

L)

0

100

200

300

4003gVS6gVS8gVS10gVS

Fig. 2. E1ect of VS concentrations on hydrogen production from the thermophilic acidogenic culture at pH 5.5.


Table 5Analysis using the thermophilic acidogenic culture at tested VS concentrations

VS H2 H2 H2 yield SHPP SHPR Lag-phase VFA (mg l1 as COD)(g l1) (ml) (%) (mol-H2/ (ml H2 g VS1) (ml H2 g VS S1 h1) time (h)

mol-hexose) TVFA HAc HPr n-HBu

3 69 23 0.9 46.1 13.7 10.7 1310 375 4 7306 274 55 1.8 91.5 12.0 17.4 3625 490 9 13158 297 64 1.5 74.1 12.0 12.4 5245 847 10 163310 350 69 1.4 70.1 19.0 18.0 5580 808 36 2237

Table 6Comparison of hydrogen yield obtained in this study to those cited in the literature

Acclimated condition of seed sludges (Substrate) Hydrogen production

HRT Temp. (oC) pH pH H2 yield Reference(mol-H2/mol-hexose)

5 day 55 1 5:6 0:2 Food waste 5.5 1.80 This study10 h 35 5:0 0:2 Rice bran 6.0 1.29 [21]12 h 60 6.8 Sugar wastewater 6.8 2.59 [20]3 day 60 6.8 Sugar wastewater 6.8 1.91 [20]10 h 35 4.55.0 Glucose 6.0 1.43 [8]6 h 35 1 5.7 Glucose 5.7 1.70 [7]

of Okamoto et al. [19] in which the maximum hydrogenproduction potential was 96 ml g VS1 from rice with 4%TS. Table 6 compares the hydrogen yield of this study withthose found in the literature.The maximum hydrogen yield of 1:8 mol-H2=mol-hexose

obtained in this study was comparable with the yield ofrice bran [21], sugar wastewater [20] and glucose [8,7].Ueno et al. [20] successfully performed continuous hydro-gen production from sugary wastewater with an yield of1:91 mol-H2=mol-hexose at 3 days HRT, 60C and pH 6.8.The biogas was composed of 64% hydrogen, 36% carbondioxide and less than 0.13% methane. From the results, itwas suggested that the thermophilic acidogenic conditioninactivating methanogenesis resulted in high yield of hydro-gen from food waste.

3.3. PCR-DGGE analysis

The microbial community in the mesophilic and ther-mophilic acidogenic culture was analyzed and compared byPCR-DGGE analysis targeted at eubacterial 16S rDNA, andthe DGGE pro@les are shown in Fig. 3.The major bands in the DGGE gels were excised and pu-

ri@ed to determine the sequence. The results of the sequenceaVliation determined by the BLAST are shown in Table 7.The number of bands detected from the mesophilic acido-genic culture was greater than that from the thermophilicacidogenic culture. This is comparable with the result of

Lapara et al. [22] who suggested that elevated temperaturecould reduce species diversity.Thermoanaerobacterium thermosaccharolyticum (band

B-1) and Desulfotomaculum geothermicum (bands B-5,B-6), which were known as hydrogen producing bacteria,appeared from the thermophilic acidogenic culture.T. thermosaccharolyticum is a thermophilic saccha-

rolytic microorganism which can produce large amountof hydrogen from carbohydrates [23]. Ueno et al. [17]studied hydrogen production by thermophilic anaerobic mi-croNora enriched from sludge compost by using an arti@cialmedium containing cellulose powder. Under all appliedculture conditions in batch and chemostat tests, microor-ganisms closely related to T. thermosaccharolyticum wereisolated and detected with strong intensity by PCR-DGGEanalysis. Ueno et al. [17] suggested that T. thermosac-charolyticum involved in acetate/butyrate fermentation ledto hydrogen production. According to the characteristicstudy of T. thermosaccharolyticum [24], the maximumgrowth of T. thermosaccharolyticum appeared at pH 5 to6, and the optimum temperature was 60C. The productionyield of hydrogen from T. thermosaccharolyticum was2:4 mol-H2=mol-glucose, a nearly equivalent hydrogen pro-duction ability to those of Clostridium butyricum whichhad hydrogen production yield of 2:4 mol-H2=mol-hexose.D. geothermicum was a thermophilic, fatty acid-degrading,sulfate-reducing bacterium [25]. Thermodesulfobacteriaclass. nov. ferment pyruvate, and principal fermentation


Fig. 3. DGGE pro@les of the PCR-ampli@ed 16S rDNA extractedfrom the mesophilic and thermophilic acidogenic culture. (A)Mesophilic acidogenic culture, and (B) thermophilic acidogenicculture.

end products were acetate, CO2, and hydrogen. Sulfateand thiosulfate were used as electron acceptor for growth,while lactate and pyruvate as electron donors for growth[26]. The DGGE-PCR analysis from the thermophilic aci-dogenic culture indicated that T. thermosaccharolyticumand Desulfotomaculum geothermicum were the microor-ganisms involved in hydrogen producing acetate/butyratefermentation.From the mesophilic acidogenic culture, bands A-2, A-9

and A-10 which were closely related to Prevotella species,Prevotella nigrescens and P. bryantii, were detected. Pre-votella species produced acetic, isobutyric, isovaleric andsuccinic acids as metabolic end products from the fer-mentation of glucose, sucrose and starch [27]. A bandaVliated with the Thermotogales strain (band A-4) that

Table 7AVliation of DGGE fragments determined by their 16S rDNAsequence

Band AVliation Similaritya Accessionno. (%) no.

A-1 Bacteroidales str.. 93 AB078832A-2 Prevotella sp. 87 AF537212A-3 TM7 phylum sp. 90 AF385506A-4 Thermotogales str. 87 AJ431248A-5 Bacillus sp. 87 AY178858A-6 Rhizosphere soil bacterium 88 AJ252680A-7 Eubacterium sp. 83 AF287761A-8 Arctic sea ice bacterium 87 AF468442A-9 P. nigrescens 89 AF414844A-10 P. bryantii 89 AY189149A-11 Bacteroidales str. 82 AF481205B-1 T. thermosaccharolytium 92 M59119B-2 TM7 phylum sp. 90 AF385506B-3 Arctic sea ice bacterium 87 AF468442B-4 P. nigrescens 89 AF414844B-5 D. geothermicum 98 AJ294428B-6 D. geothermicum 98 AJ294428

aPercentage similarity to the closest relative according to theBLAST comparison.

produced acetate, CO2 and H2 from the fermentation of glu-cose, was detected [28]. A band aVliated with the Bacillusspecies (band A-5) that produced H2, was detected [29], andthe Bacteroidales strain (band A-1, A-11) which producedsuccinate, acetate, lactate, formate, or propionate from thefermentation of carbohydrate or peptone, was also detected[30]. Bands each aVliated with the TM7 phylum species(band A-3, B-2) [31], Arctic sea ice bacterium (band A-8,B-3) [32], Rhizosphere soil bacterium (band A-6) [33]which were not related to hydrogen production, were de-tected. TM7 phylum species, Arctic sea ice bacterium andP. nigrescens, were detected from both thermophilic andmesophilic culture.

4. Conclusions

Thermophilic acidogenesis acclimated with food wasteat 5 days HRT which was enough HRT for the acidi@-cation of the waste showed e1ective hydrogen produc-tion. The thermophilic condition had inhibitory e1ect onmethane and propionate production. The higher hydrogenproduction from the thermophilic acidogenic culture thanthe mesophilic acidogenic culture was caused by free ofmethane and negligible propionate which were hydrogenconsumers. Increase of VS concentrations resulted in theincrease of quantity and quality of hydrogen production.Hydrogen producing microorganisms of T. thermosaccha-rolytium andD. geothermicum were detected from the ther-mophilic acidogenic culture, while Thermotogales strain


and Bacillus species were detected from the mesophilic aci-dogenic culture by PCR-DGGE analysis. The results of thisstudy showed the feasibility of hydrogen production fromcarbohydrate-rich organic solid wastes such as food wasteat enough HRT for the wastes acidi@cation by thermophilicacidogenesis.

Acknowledgements

This work was supported by grant No. M1-0203-00-0063from the National Research Laboratory Program of the Ko-rean Ministry of Science and Technology.

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Hydrogen production from food waste in anaerobic mesophilic and thermophilic acidogenesisIntroductionMaterials and methodsFeedstockSeed microorganismsExperimental apparatus and procedureAnalyses

Results and discussionEffect of pH on hydrogen productionEffect of VS concentrations on hydrogen productionPCR-DGGE analysis

ConclusionsAcknowledgementsReferences

Documents

Hydrogen Production From Food Waste in Anaerobic Mesophilic and Thermophilic Acidogenesis