title: Bioethanol production from the nutrient stress-induced microalga Chlorella vulgaris by enzymatic hydrolysis and immobilized yeast fermentation.
abstract: The microalga Chlorella vulgaris is a potential feedstock for bioenergy due to its rapid growth, carbon dioxide fixation efficiency, and high accumulation of lipids and carbohydrates. In particular, the carbohydrates in microalgae make them a candidate for bioethanol feedstock. In this study, nutrient stress cultivation was employed to enhance the carbohydrate content of C. vulgaris. Nitrogen limitation increased the carbohydrate content to 22.4% from the normal content of 16.0% on dry weight basis. In addition, several pretreatment methods and enzymes were investigated to increase saccharification yields. Bead-beating pretreatment increased hydrolysis by 25% compared with the processes lacking pretreatment. In the enzymatic hydrolysis process, the pectinase enzyme group was superior for releasing fermentable sugars from carbohydrates in microalgae. In particular, pectinase from Aspergillus aculeatus displayed a 79% saccharification yield after 72h at 50°C. Using continuous immobilized yeast fermentation, microalgal hydrolysate was converted into ethanol at a yield of 89%.
authors: Department of Bioenergy Science and Technology, Chonnam National University, Gwangju 500-757, Republic of Korea.
authors: Kyoung Hyoun
authors: KH
authors: Kim
authors: Department of Wood Science and Landscape Architecture, Chonnam National University, Gwangju 500-757, Republic of Korea.
authors: In Seong
authors: IS
authors: Choi
authors: Department of Bioenergy Science and Technology, Chonnam National University, Gwangju 500-757, Republic of Korea.
authors: Ho Myeong
authors: HM
authors: Kim
authors: Bio-Energy Research Center, Chonnam National University, Gwangju 500-757, Republic of Korea.
authors: Seung Gon
authors: SG
authors: Wi
authors: Department of Bioenergy Science and Technology, Chonnam National University, Gwangju 500-757, Republic of Korea; Department of Wood Science and Landscape Architecture, Chonnam National University, Gwangju 500-757, Republic of Korea; Bio-Energy Research Center, Chonnam National University, Gwangju 500-757, Republic of Korea. Electronic address: baehj@chonnam.ac.kr.
authors: Hyeun-Jong
authors: HJ
authors: Bae
mesh_terms: D056804:Biofuels / Q000382:microbiology*; D018533:Biomass; D001709:Biotechnology / Q000379:methods*; D050260:Carbohydrate Metabolism / Q000187:drug effects; D018914:Cells, Immobilized / Q000187:drug effects / Q000378:metabolism; D048408:Chlorella vulgaris / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation / Q000187:drug effects; D006868:Hydrolysis / Q000187:drug effects; D058086:Microalgae / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D009005:Monosaccharides / Q000032:analysis; D009584:Nitrogen / Q000494:pharmacology; D011096:Polygalacturonase / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism*; D013312:Stress, Physiological / Q000187:drug effects
chemical_list: D056804:Biofuels; D009005:Monosaccharides; D000431:Ethanol; D011096:Polygalacturonase; D009584:Nitrogen
keywords: Bioethanol; Chlorella vulgaris; Enzymatic saccharification; Microalgae; Nitrogen stress