Effects of oxygen supply on yeast growth and metabolism in continuous fermentation |
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| Institution: | 1. Biotechnology Department, Engineering School of Lorena, University of São Paulo, Estrada Municipal do Campinho s/n, CEP 12602-810, Lorena, São Paulo, Brazil;2. Engineering Processes Sector, Food Technology Department, State University of the North Fluminense, Av Alberto Lamego 2000, Pq California, Zip code: 28013-602, Campos dos Goytacazes, Rio de Janeiro, Brazil;1. College of Materials Science and Engineering, Nanjing Tech University, Nanjing, 210009, China;2. Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites, Nanjing Tech University, Nanjing, 210009, China;3. Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing Tech University, Nanjing, 210009, China;1. State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China;2. Shanghai Collaborative Innovation Center for Biomanufacturing, Shanghai 200237, China;3. Bioprocessing Technology Institute, Singapore;4. Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore;1. GlycoFi/Biologics Discovery, Merck & Co., Inc., 16 Cavendish Ct., Lebanon, NH 03766, USA;2. ASL Analytical Inc., 2500 Crosspark Rd, Coralville, IA 52241, USA;1. Università degli Studi di Torino, Dipartimento di Scienze Agrarie, Forestali e Alimentari, Largo Braccini 2, 10095 Grugliasco, Italy;2. Istituto di Enologia e Ingegneria Agro-Alimentare, Università Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy;3. Lallemand SAS, Blagnac, France |
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| Abstract: | The yield changes in cell mass and metabolites with changes in the oxygen supply rate were investigated in continuous ethanol fermentation. With increases in oxygen concentration in the purging gas from 5.3 to 39.3 %, the specific oxygen uptake rate (qO2) increased from 0.158 to 1.24 mmol/g/h. With this change, cell mass increased from 13.2 to 14.9 g/l and glycerol decreased from 4.8 to 0.99 g/l, although little change in ethanol yield was observed. At a higher oxygen concentration and/or at a lower respiratory quotient (RQ), glycerol disappeared, acetaldehyde, acetoin and 2,3-butanediol increased, and ethanol started to decrease. The yields of iso-butylalcohol and iso-amylalcohol also increased with increases in the oxygen supply rate when RQ was lower than approximately 10. Reduction in the redox balance (NADH/NAD) in the cells by qO2, appeared to reduce initially the rate of glycerol-3-phosphate formation and next the rate of ethanol formation, resulting in the accumulation of acetaldehyde and formation of 2,3-butanediol through acetoin. Fatty acid composition changed with changes in the oxygen supply rate. The value for unsaturation, Δ mol−1, increased from 0.745 to 0.836 with the increase in qO2 from 0.158 to 1.79 mmol/g/h. Increases in oleic acid (C18:1) and decreases in palmitic acid (C16:0) were the major changes with the increases in Δ mol−1. |
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