Feasibility of CO2mitigation and carbohydrate production by microalgaScenedesmus obliquusCNW-N used for bioethanol fermentation under outdoor conditions: effects of seasonal changes.
BACKGROUND
Although outdoor cultivation systems have been widely used for mass production of microalgae at a relatively low cost, there are still limited efforts on outdoor cultivation of carbohydrate-rich microalgae that were further used as feedstock for fermentative bioethanol production. In particular, the effects of seasonal changes on cell growth, CO2fixation, and carbohydrate production of the microalgae have not been well investigated.


RESULTS
This work demonstrates the feasibility of using outdoor tubular photobioreactors (PBR) for whole-year-round cultivation of a carbohydrate-rich microalgaScenedesmus obliquusCNW-N in southern Taiwan. Time-course profile of the carbohydrate content under nitrogen-deficient conditions was monitored to assess the seasonal changes. The optimal CO2fixation rate and carbohydrate productivity were 430.2 mg L-1d-1and 111.8 mg L-1d-1, respectively, which were obtained during the summer time. Under nitrogen starvation, the microalgal biomass can accumulate nearly 45-50% of carbohydrates, mainly composed of glucose that accounted for 70-80% of the total carbohydrates in the microalgal cells. This glucose-rich microalgal biomass is apparently a very suitable carbon source for bioethanol fermentation.


CONCLUSIONS
This work shows the feasibility of combining CO2fixation and bioethanol production using microalgae grown in outdoor photobioreactors as feedstock. The understanding of the seasonal changes in the carbohydrate productivity makes this approach more practically viable. The novel strategy proposed in this study could be a promising alternative to the existing technology dealing with CO2mitigation and biofuels production.
State Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute Technology, Harbin, People's Republic of China.
Shih-Hsin
SH
Ho
State Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute Technology, Harbin, People's Republic of China.
Yi-Di
YD
Chen
Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan.
Ching-Yu
CY
Chang
Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan.
Yen-Ying
YY
Lai
Center for Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan.
Chun-Yen
CY
Chen
Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, 657-8501 Japan.|Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, 3-5 Sanbancho, Chiyoda-ku, Tokyo, 102-0075 Japan.|Biomass Engineering Program, RIKEN, 1-7-22 Suehiro, Tsurumi-ku, Yokohama, 230-0045 Japan.
Akihiko
A
Kondo
State Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute Technology, Harbin, People's Republic of China.
Nan-Qi
NQ
Ren
State Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute Technology, Harbin, People's Republic of China.|Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan.|Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan, Taiwan.
Jo-Shu
JS
Chang
Bioethanol production; CO2 fixation; Carbohydrate; Microalgae; Outdoor cultivation; Seasonal changes