The effect of culture conditions on the morphology of the dimorphic yeast Kluyveromyces marxianus var. marxianus NRRLy2415: a study incorporating image analysis

Abstract

The effect of changing environmental conditions on the morphology of the yeast Kluyveromyces marxianus var. marxianus NRRLy2415 was investigated in batch and continuous culture, using a previously developed computer-aided image analysis protocol [O'Shea and Walsh (1996) Biotechnol Bioeng 51: 679 690]. The morphology of the organism is primarily controlled by the specific growth rate, mu. This finding was contrary to a previous investigation [Walker and O'Neill (1990) J Chem Tech Biotechnol 49: 75-89]. When the organism is cultured in batch with excess oxygen, mu can approach the maximum specific growth rate, microm, and the primary morphology of the culture is yeast-like. However, if the organism is cultured in a chemostat, thereby controlling the growth rate, the morphology reverts to a pseudohyphal form. This response is thought to be an adaptation by the organism to its environment, whereby it assumes a foraging form under adverse environmental conditions. The use of computer-aided image analysis made possible the discrimination of subtle morphological differences between samples and the determination of the relationship between morphology and growth rate.

The modeling of ethanol production by Kluyveromyces marxianus using whey as substrate in continuous A-Stat bioreactors

“…The predominant elongated yeast morphology of Klyuveromyces marxianus CCT 4086 was verified. This observation was also reported by O' Shea and Walsh [36] using the same strain K. marxianus CCT 4086 (NRRLy2415) and for similar dilution rates.…”

“…Despite these changes in concentrations, cell washout was not observed, and a second cell metabolism stabilization appears to be reached for D between 0.15 and 0.17 h −1 . Although some researchers reported the influence of dilution rate on the cell morphology, suggesting that even small changes in growth rate could result in significant transitions in morphology [18,36], in this work, no changes in cell morphology were observed for dilution rates between 0.05 and 0.1 h −1 . The predominant elongated yeast morphology of Klyuveromyces marxianus CCT 4086 was verified.…”

Physiological diversity within the kluyveromyces marxianus species

“…While in the middle-range (higher than 0.15 h -1 and lower than 0.4 h -1 ), the cells show the dominant yeast-like morphology. On the other hand, at lower or higher growth rates cells show a filamentous/pseudohyphal shape (O'Shea and Walsh 2000). This characteristic could be explored industrially for protein secretion, since filamentous cells are known to have better secreting properties than yeast-like cells (McIntyre et al 2002).…”

“…The former strain possesses a high capacity of producing inulinase (Rouwenhorst et al 1988) and is cited in a large number of academic studies involving K. marxianus, including recent works on the successful expression of different heterologous proteins (Rocha et al 2010;Rocha et al 2011). K. marxianus CBS 397 presents dimorphism, depending on the culture conditions (O'Shea and Walsh 2000). K. marxianus CBS 712 T is the species type-strain and was isolated from grapes by E.C.…”

The Effects of Osmotic Pressure and Ethanol on Yeast Viability and Morphology

“…The degree of inhibition is related to environmental factors and is strain dependent. Although the effects of high gravity brewing have been extensively studied 3,5,9,19,32,40 and numerous morphological studies have been able to successfully link changes in morphology to some physiological feature of the yeast cell 1,15,21,29,30,35 , little research has been conducted on the effect of this process on yeast cell volume and the applicability of this tool in the selection of yeast strains that will successfully ferment high gravity worts in a production environment. In this study, we examined the effects of osmotic and ethanol stresses on the cell volume and viability of lager and ale yeast strains.…”