Growth, substrate consumption and metabolite formation during aerobic batch cultivations of Kluyveromyces marxianus CBS 6556 on different carbon sources.
Gustavo Graciano Fonseca (1), Nuno Miguel Barbosa de Carvalho (1), Andreas Karoly Gombert (2)
(1) Chemical Engineering, University of Sao Paulo, C.P. 61548, Sao Paulo, SP, 05424-970, Brazil; (2) University of Sao Paulo, Department of Chemical Engineering, C.P. 61548, 05424-970, Sao Paulo-SP, Brazil
Although the yeast Kluyveromyces marxianus presents many characteristics which make it an attractive host for the production of biomass-linked compounds, there is a lack of information on the physiology of this organism, a pre-requisite for its future use as a cell-factory and to be a target of metabolic engineering strategies. In this work, the kinetics of growth, substrate consumption, and metabolite formation during aerobic batch cultures of K. marxianus CBS 6556 was investigated. A defined medium was used, in which either glucose (GLC), lactose (LAC), galactose (GAL), fructose, or sucrose were the sole carbon source. Growth on some binary mixtures of sugars was also investigated. Our results confirm that this yeast presents: a very low tendency to form ethanol and other products under aerobic conditions (a maximum yield of 0.05 g total products/g sugar was observed); high growth rates (always around 0.45 h -1 , except for growth on GAL); high biomass yields (always around 0.55 g dry weight/g sugar); and similar growth behavior at 30 and at 37 o C. The behavior on sugar mixtures shows that diauxic growth occurs on the GLC/LAC and on the GLC/GAL mixtures, but not on the LAC/GAL mixture. Although this yeast presents faster growth on LAC than on GAL alone, the consumption of GAL after growth on GLC is faster than the consumption of LAC after growth on GLC. Acknowledgments to FAPESP. Two first authors contributed equally to this work.