Microbial granulation for lactic acid production.
This work investigated the formation of microbial granules to boost the productivity of lactic acid (LA). The flocculated form of LA-producing microbial consortium, dominated by Lactobacillus sp. (91.5% of total sequence), was initially obtained in a continuous stirred-tank reactor (CSTR), which was fed with 2% glucose and operated at a hydraulic retention time (HRT) of 12 h and pH 5.0 ± 0.1 under a thermophilic condition (50°C). The mixed liquor in the CSTR was then transferred to an up-flow anaerobic sludge blanket reactor (UASB). The fermentation performance and granulation process were monitored with a gradual decrease of HRT from 8.0 to 0.17 h, corresponding to an increase in the substrate loading from 60 to 2,880 g glucose L(-1) d(-1) . As the operation continued, the accumulation of biomass in the UASB was clearly observed, which changed from flocculent to granular form with decrease in HRT. Up to the HRT decrease to 0.5 h, the LA concentration was maintained at 19-20 g L(-1) with over 90% of substrate removal efficiency. However, further decrease of HRT resulted in a decrease of LA concentration with increase in residual glucose. Nevertheless, the volumetric LA productivity continuously increased, reaching 67 g L-fermenter (-1) h(-1) at HRT 0.17 h. The size of LA-producing granules and hydrophobicity gradually increased with decrease in HRT, reaching 6.0 mm and 60%, respectively. These biogranules were also found to have high settling velocities and low porosities, ranging 2.69-4.73 cm s(-1) and 0.39-0.92, respectively.
Department of Civil Engineering, Inha University, 100 Inharo, Nam-gu, Incheon, 402-751, Republic of Korea.
Dong-Hoon
DH
Kim
Biomass and Waste Energy Laboratory, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon, 305-343, Republic of Korea.
Mo-Kwon
MK
Lee
Department of Environmental Engineering, Technical University of Denmark, Miljøvej, Bygning 113, DK-2800 Kgs. Lyngby, Denmark.|Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701, Republic of Korea.
Yuhoon
Y
Hwang
Department of Biotechnology, Hankyoung National Univeristy, 327 Chungang-no Anseong-si, Kyonggi-do, 456-749, Republic of Korea.
Wan-Taek
WT
Im
Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701, Republic of Korea.
Yeo-Myeong
YM
Yun
Department of Civil and Environmental Engineering, University of Massachusetts Amherst, 130 Natural Resources Road, Amherst, Massachusetts, 01003.
Chul
C
Park
Biomass and Waste Energy Laboratory, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon, 305-343, Republic of Korea. bmmskim@kier.re.kr.|Division of Renewable Energy Engineering, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon, 305-350, Republic of Korea. bmmskim@kier.re.kr.
Mi-Sun
MS
Kim
D000693:Anaerobiosis; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology; D005427:Flocculation; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000378:metabolism*; D007778:Lactobacillus / Q000254:growth & development / Q000378:metabolism*; D059013:Microbial Consortia; D013696:Temperature; D013997:Time Factors
D019344:Lactic Acid; D005947:Glucose
lactic acid; microbial granules; pyrosequencing; settling experiments; up-flow anaerobic sludge blanket reactor; volumetric productivity