Expression of AtMed15 of Arabidopsis in yeast causes flocculation and increases ethanol production in yeast culture

Abstract

Mediator, a multiprotein complex involved in transcription of class II genes, was first discovered in yeast and then characterized in many metazoans revealing a striking structural conservation of the complex. However, sequences of Mediator subunits are not well conserved raising a question on the functional conservation of these individual subunits. In this study, expression of Med15 of Arabidopsis (AtMed15) in gal11∆ yeast could not complement the function of ScGal11 in galactose metabolism and resistance against cycloheximide. Surprisingly, AtMed15 changed the morphology of the yeast cells. The cells adhered strongly on the surface of the agar media, and showed robust flocculation in the liquid media without affecting the growth. The AtMed15-induced adhesion and flocculation were observed in different carbon sources. Calcium-assisted cell wall-bound mannan-binding proteins were found to be involved in this flocculation, which was unaffected by wide fluctuation of pH or temperatures revealing its constitutive robust nature. Expression of few flocculation related Flo genes was up-regulated in these cells. Interestingly, there was significant increase in ethanol production by the yeast expressing AtMed15. Robust and constitutive flocculation and increased ethanol production by yeast cells harbouring AtMed15 indicate an opportunity of its important usage in biotechnology industries.

Expression of C-5 sterol desaturase from an edible mushroom in fisson yeast enhances its ethanol and thermotolerance

“…Recently, increased ethanol production was achieved in yeast by expression of AtMed15 of Arabidopsis which led to increased flocculation [9]. The resistance of yeast to high temperature and ethanol concentration are desirable characteristics for production of bioethanol [10].…”

“…Genetic improvement of yeast to obtain strains that can combat or adapt to extreme conditions of stress, is an important strategy to ensure the competitiveness of a fermentation process. Recently, increased ethanol production was achieved in yeast by expression of AtMed15 of Arabidopsis which led to increased flocculation [ 9 ]. The resistance of yeast to high temperature and ethanol concentration are desirable characteristics for production of bioethanol [ 10 ].…”

Possible Role for Allelic Variation in Yeast MED15 in Ecological Adaptation

“…These and other studies found that MED15 was also required for flocculation and adhesion ( Barrales et al, 2008 ; Fidalgo et al, 2008 ). Finally, overexpression of Arabidopsis thaliana MED15 in wild type strains of S. cerevisiae led to increased flocculation, adhesion and a significant increase in ethanol production ( Dahiya et al, 2016 ).…”

Production of ethanol from Jerusalem artichoke by mycelial pellets

“…For example, fermentable sugars can be obtained by enzymatic hydrolysis of inulin directly, which has the characteristics of simple process without high temperature liquefaction and low energy consumption. Compared with crop straw which is the representative of lignocellulosic biomass, ethanol production by inulin fermentation is easier to industrialize 9–11 . In addition, JA has the advantages of the high carbohydrate yields (5 and 14 ton/ha) and large-scale cultivation.…”