Optimization of temperature, sugar concentration, and inoculum size to maximize ethanol production without significant decrease in yeast cell viability

Author(s)

Laluce, Cecilia ^[1] ; Tognolli, Joao Olimpio ^[2] ; de Oliveira, Karen Fernanda ^[3] ; Souza, Crisla Serra ^[3] ; Morais, Meline Rezende ^[1]

Affiliation

^[1] Univ Estadual Paulista, Inst Quim Araraquara, Dept Biochem & Biotechnol Chem, BR-14801970 Sao Paulo - Brazil

^[2] Univ Estadual Paulista, Inst Quim Araraquara, Dept Analyt Chem, BR-14801970 Sao Paulo - Brazil

^[3] Inst Biomed Sci, Programa Posgrad Interunidades Biotecnol, BR-05508900 Sao Paulo - Brazil

• Document type: Journal article
• Source: Applied Microbiology and Biotechnology; v. 83, n. 4, p. 627-637, June 2009.
• Field of knowledge: Biological Sciences - Microbiology
• Web of Science Citations: 39

Abstract

Aiming to obtain rapid fermentations with high ethanol yields and a retention of high final viabilities (responses), a 23 full-factorial central composite design combined with response surface methodology was employed using inoculum size, sucrose concentration, and temperature as independent variables. From this statistical treatment, two well-fitted regression equations having coefficients significant at the 5% level were obtained to predict the viability and ethanol production responses. Three-dimensional response surfaces showed that increasing temperatures had greater negative effects on viability than on ethanol production. Increasing sucrose concentrations improved both ethanol production and viability. The interactions between the inoculum size and the sucrose concentrations had no significant effect on viability. Thus, the lowering of the process temperature is recommended in order to minimize cell mortality and maintain high levels of ethanol production when the temperature is on the increase in the industrial reactor. Optimized conditions (200 g/l initial sucrose, 40 g/l of dry cell mass, 30 °C) were experimentally confirmed and the optimal responses are 80.8+-2.0 g/l of maximal ethanol plus a viability retention of 99.0+-3.0% for a 4-h fermentation period. During consecutive fermentations with cell reuse, the yeast cell viability has to be kept at a high level in order to prevent the collapse of the process. (AU)

• FAPESP's process: 05/02840-0 - Enzymatic obtaining of xylitol using Candida guilliermondii xylose reductase as an alternative to fermentative production pathway
• Grantee: Ricardo de Freitas Branco
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)