Comparative transcriptome analysis between original and evolved recombinant lactose-consuming Saccharomyces cerevisiae strains

Pedro Guimarães (1) , Véronique Le Berre (2, 3) , Serguei Sokol (3) , Jean François (4, 3) , José Teixeira (5) , Lucília Domingues (6)

1 INESC TEC - Institute for Systems and Computer Engineering, Technology and Science [Braga]
2 Biochip and Bionanotechnogy
3 LISBP - Laboratoire d'Ingénierie des Systèmes Biologiques et des Procédés
4 ITAV - Institut des Technologies Avancées en sciences du Vivant
5 LLB - UMR 12 - Laboratoire Léon Brillouin
6 IBB - Institute for Biotechnology and Bioengineering

Cheese whey is a highly pollutant by-product of dairy industries that is produced in high amounts [1]. The lactose in whey (about 5%) is interesting as a substrate for the production of a variety of products , including bio-ethanol [1]. However, the yeast Saccharomyces cerevisiae, which is most frequently the microorganism of choice for alcoholic fermentation bioprocesses, is unable to metabolize lactose, unlike some other yeasts such as Kluyveromyces species. A recombinant S. cerevisiae flocculent strain that expressed both the LAC4 (β-galactosidase) and LAC12 (lactose permease) genes of Kluyveromyces lactis was previously constructed [2]. The original recombinant strain (NCYC869-A3/T1, hereafter referred as T1) metabolized lac-tose slowly and its flocculation performance was poor when compared to the strongly flocculent host strain. Hence, the recombinant T1 was subjected to a long-term evolutionary engineering experiment (previously described; [3]), designed to keep the re-combinant growing in lactose for many generations , as well as to select for flocculent cells. That experiment yielded an evolved recombinant (strain T1-E) that efficiently fermented lactose to ethanol. In lactose cultivations, the evolved strain showed improved growth rate, ethanol productivity and yield, as well as improved flocculation, compared to the original recombinant [3]. At the molecular level , we found two alterations that targeted the LAC The engineering of Saccharomyces cerevisiae strains for lactose utilization has been attempted with the intent of developing high productivity processes for alcoholic fermentation of cheese whey. A recombinant S. cerevisiae flocculent strain that efficiently ferments lactose to ethanol was previously obtained by evolutionary engineering of an original recombinant that displayed poor lactose fermentation performance. We compared the transcriptomes of the original and the evolved re-combinant strains growing in lactose, using cDNA microarrays. Microarray data revealed 173 genes whose expression levels differed more than 1.5-fold. About half of these genes were related to RNA-mediated transposition. We also found genes involved in DNA repair and recombination mechanisms, response to stress, chromatin remodeling, cell cycle control, mitosis regulation, gly-colysis and alcoholic fermentation. These transcriptomic data are in agreement with some of the previously identified physiological and molecular differences between the recombinants, and point to further hypotheses to explain those differences.

Domaines: Sciences du Vivant [q-bio]; Biochimie, Biologie Moléculaire

Pedro Guimarães, Véronique Le Berre, Serguei Sokol, Jean François, José Teixeira, et al.. Comparative transcriptome analysis between original and evolved recombinant lactose-consuming Saccharomyces cerevisiae strains. Biotechnology Journal, 2008, 3 (12), pp.1591 - 1597. ⟨10.1002/biot.200800111⟩. ⟨hal-01849388⟩