title: Improvement of a continuous ethanol fermentation from sweet sorghum stem juice using a cell recycling system.
abstract: The process variables (aeration rate and recycle ratio) of a continuous ethanol fermentation with a cell recycling system (CRS) by Saccharomyces cerevisiae NP 01 from sweet sorghum stem juice were optimized using response surface methodology (RSM). The relationship between intracellular composition and fermentation efficiency was also investigated. RSM results revealed that the optimum aeration rate and recycle ratio were 0.25vvm and 0.625, respectively. The validation experiment under the optimum conditions indicated high precision and reliability of the experiment, achieving an actual ethanol concentration (PE) of 99.28g/l, which was very close to the predicted value (98.01g/l), and a very high ethanol productivity (QP) of 7.94g/lh. The intracellular composition of the yeast cells (i.e., unsaturated fatty acids (UFAs), total fatty acids (TFAs), ergosterol and trehalose) was positively related to the fermentation efficiency and yeast adaptive response under ethanol stress. A higher ratio of UFAs/TFAs and ergosterol strongly promoted yeast viability and ethanol fermentation. Additionally, high trehalose content was observed when the yeast was subjected to stress conditions.
authors.affiliation: Graduate School, Khon Khon University, Khon Kaen 40002, Thailand.
authors.forename: Arthit
authors.initials: A
authors.lastname: Thani
authors.affiliation: Department of Biotechnology, Faculty of Technology, Khon Kaen University, Khon Kaen 40002, Thailand; Fermentation Research Center for Value Added Agricultural Products, Khon Kaen University, Khon Kaen 40002, Thailand.
authors.forename: Pattana
authors.initials: P
authors.lastname: Laopaiboon
authors.affiliation: Department of Biotechnology, Faculty of Technology, Khon Kaen University, Khon Kaen 40002, Thailand; Fermentation Research Center for Value Added Agricultural Products, Khon Kaen University, Khon Kaen 40002, Thailand. Electronic address: lakcha@kku.ac.th.
authors.forename: Lakkana
authors.initials: L
authors.lastname: Laopaiboon
mesh_terms: D004875:Ergosterol / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D005285:Fermentation; D010936:Plant Extracts / Q000378:metabolism*; D018547:Plant Stems; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D045868:Sorghum; D013312:Stress, Physiological; D014199:Trehalose / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D010936:Plant Extracts; D000431:Ethanol; D014199:Trehalose; D004875:Ergosterol
keywords: Aeration; Bioethanol; Cell recycle; Continuous fermentation; Saccharomyces; Sweet sorghum