Browsing by Author "Ong, Seow-Chin"

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Characterization of the thermal-tolerant mutants of Chlorella sp with high growth rate and application in outdoor photobioreactor cultivation
(2010-04-01)
Ong, Seow-Chin
;
Kao, Chien-Ya
;
Chiu, Sheng-Yi
;
Tsai, Ming-Ta
;
Lin, Chih-Sheng
In this study, two thermal-tolerant mutants of Chlorella sp. MT-7 and MT-15, were isolated. In indoor cultivation, specific growth rate (mu, d(-1)) of the mutants were 1.4 to 1.8-fold at 25 degrees C and 3.3 to 6.7-fold at 40 C higher than those of wild type. The carbon dioxide fixation rate of both microalgal mutants was also significantly higher than that of wild type. In outdoor closed cultivation, where the temperature of culture broth was 41 +/- 1 degrees C, the mu of mutant strain MT-15 was 0.238 d(-1) during an 8-day cultivation. Whereas, the growth of wild type was inhibited in the outdoor cultivation. Our results show that the isolated microalgal strains are adaptable to be applied in outdoor cultivation in subtropical zones. (C) 2009 Elsevier Ltd. All rights reserved.
Lipid accumulation and CO(2) utilization of Nannochloropsis oculata in response to CO(2) aeration
(2009-01-01)
Chiu, Sheng-Yi
;
Kao, Chien-Ya
;
Tsai, Ming-Ta
;
Ong, Seow-Chin
;
Chen, Chiun-Hsun
In order to produce microalgal lipids that can be transformed to biodiesel fuel, effects of concentration of CO(2) aeration on the biomass production and lipid accumulation of Nannochloropsis oculata in a semicontinuous culture were investigated in this study. Lipid content of N. oculata cells at different growth phases was also explored. The results showed that the lipid accumulation from logarithmic phase to stationary phase of N. oculata NCTU-3 was significantly increased from 30.8% to 50.4%. In the microalgal cultures aerated with 2%, 5%, 10% and 15% CO(2), the maximal biomass and lipid productivity in the semicontinuous system were 0.480 and 0.142 g L(-1) d(-1) with 2% CO(2) aeration, respectively. Even the N. oculata NCTU-3 cultured in the semicontinuous system aerated with 15% CO(2), the biomass and lipid productivity could reach to 0.372 and 0.084 g L(-1) d(-1), respectively. In the comparison of productive efficiencies, the semicontinuous system was operated with two culture approaches over 12 d. The biomass and lipid productivity of N. oculata NCTU-3 were 0.497 and 0.151 g L(-1) d(-1) in one-day replacement (half broth was replaced each day), and were 0.296 and 0.121 g L(-1) d(-1) in three-day replacement (three fifth broth was replaced every 3 d), respectively. To optimize the condition for long-term biomass and lipid yield from N. oculata NCTU-3, this microalga was suggested to grow in the semicontinuous system aerated with 2% CO(2) and operated by one-day replacement. (C) 2008 Elsevier Ltd. All rights reserved.
Microalgal biomass production and on-site bioremediation of carbon dioxide, nitrogen oxide and sulfur dioxide from flue gas using Chlorella sp cultures
(2011-10-01)
Chiu, Sheng-Yi
;
Kao, Chien-Ya
;
Huang, Tzu-Ting
;
Lin, Chia-Jung
;
Ong, Seow-Chin
The growth and on-site bioremediation potential of an isolated thermal- and CO(2)-tolerant mutant strain. Chlorella sp. MTF-7, were investigated. The Chlorella sp. MTF-7 cultures were directly aerated with the flue. gas generated from coke oven of a steel plant. The biomass concentration, growth rate and lipid content of Chlorella sp. MTF-7 cultured in an outdoor 50-L photobioreactor for 6 days was 2.87 g L(-1) (with an initial culture biomass concentration of 0.75 g L(-1)), 0.52 g L(-1) d(-1) and 25.2%, respectively. By the operation with intermittent flue gas aeration in a double-set photobioreactor system, average efficiency of CO(2) removal from the flue gas could reach to 60%, and NO and SO(2) removal efficiency was maintained at approximately 70% and 50%, respectively. Our results demonstrate that flue gas from coke oven could be directly introduced into Chlorella sp. MTF-7 cultures to potentially produce algal biomass and efficiently capture CO(2), NO and SO(2) from flue gas. (C) 2011 Elsevier Ltd. All rights reserved.
Reduction of CO2 by a high-density culture of Chlorella sp in a semicontinuous photobioreactor
(2008-06-01)
Chiu, Sheng-Yi
;
Kao, Chien-Ya
;
Chen, Chiun-Hsun
;
Kuan, Tang-Ching
;
Ong, Seow-Chin
The microalga incorporated photobioreactor is a highly efficient biological system for converting CO2 into biomass. Using microalgal photobioreactor as CO2 mitigation system is a practical approach for elimination of waste gas from the CO2 emission. In this study, the marine microalga, Chlorella sp. was cultured in a photobioreactor to assess biomass, lipid productivity and CO2 reduction. We also determined the effects of cell density and CO2 concentration on the growth of Chlorella sp. During an 8-day interval cultures in the semicontinuous cultivation, the specific growth rate and biomass of Chlorella sp. cultures in the conditions aerated 2-15% CO2 were 0.58-0.66 d(-1) and 0.76-0.87g L-1, respectively. At CO2 concentrations of 2%, 5%, 10% and 15%, the rate of CO2, reduction was 0.261, 0.316, 0.466 and 0.573 g h(-1), and efficiency of CO2 removal was 58%, 27%, 20% and 16%, respectively. The efficiency of CO2 removal was similar in the single photobioreactor and in the six-parallel photobioreactor. However, CO2 reduction, production of biomass, and production of lipid were six times greater in the six-parallel photobioreactor than those in the single photobioreactor. In conclusion, inhibition of microalgal growth cultured in the system with high CO2 (10-15%) aeration could be overcome via a high-density culture of microalgal inoculum that was adapted to 2% CO2. Moreover, biological reduction of CO2 in the established system could be parallely increased using the photo bioreactor consisting of multiple units. (c) 2007 Elsevier Ltd. All rights reserved.
The air-lift photobioreactors with flow patterning for high-density cultures of microalgae and carbon dioxide removal
(2009-06-01)
Chiu, Sheng-Yi
;
Tsai, Ming-Ta
;
Kao, Chien-Ya
;
Ong, Seow-Chin
;
Lin, Chih-Sheng
A photobioreactor containing microalgae is a highly efficient system for converting carbon dioxide (CO(2)) into biomass. Using a microalgal photobioreactor as a CO(2) mitigation system is a practical approach to the problem Of CO(2) emission from waste gas. In this study, a marine microalga, Chlorella sp. NCTU-2, was applied to assess biomass production and CO(2) removal. Three types of photobioreactors were designed and used: (i) without inner column (i.e. a bubble column), (ii) with a centric-tube column and (iii) with a porous centric-tube column. The specific growth rates (it) of the batch cultures in the bubble column, the centric-tube and the porous centric-tube photobioreactor were 0.180, 0.226 and 0.252 day(-1), respectively. The porous centric-tube photobioreactor, operated in semicontinuous culture mode with 10% CO(2) aeration, was evaluated. The results show that the maximum biomass productivity was 0.61 g/L when one fourth of the culture broth was recovered every 2 days. The CO(2) removal efficiency was also determined by measuring the influent and effluent loads at different aeration rates and cell densities of Chlorella sp. NCTU-2. The results show that the CO(2), removal efficiency was related to biomass concentration and aeration rate. The maximum CO(2) removal efficiency of the Chlorella sp. NCTU-2 culture was 63% when the biomass was maintained at 5.15 g/L concentration and 0.125 vvm aeration (volume gas per volume broth per min; 10% CO(2) in the aeration gas) in the porous centric-tube photobioreactor.