Identification of candidate genes for yeast engineering to improve bioethanol production in very high gravity and lignocellulosic biomass industrial fermentations

Table 4 Effect of the expression of genes required for tolerance to inhibitory concentrations of ethanol, acetic acid and furfural or vanillin in the fermentation of a wheat straw hydrolysate.

Strain	[Ethanol] (g/L)	ΔEthanol (compared to wild-type cells)	[CO₂] at mid-fermentation (g/L)	ΔCO₂ (compared to wild-type cells)
BY4741	21 ± 2	0	8 ± 1	0
Stress: Acetic acid, ethanol and furfural
Δnat3	22 ± 0	1 ± 2	8 ± 1	7 ± 11
Δppa1	21 ± 0	1 ± 0	12 ± 0	44 ± 8 **
Δprs3	20 ± 0	-5 ± 1	3 ± 1	-50 ± 9 **
Δrpb4	3 ± 0	-85 ± 2 **	0 ± 0	-78 ± 11 **
Δvma8	7 ± 1	-63 ± 5 **	0 ± 1	-80 ± 11 **
Stress: Acetic acid, ethanol and vanillin
Δend3	21 ± 0	-1 ± 2	5 ± 2	-33 ± 20
Δerg2	20 ± 1	-5 ± 3	2 ± 0	-256 ± 68 **
Δerg24	21 ± 0	-1 ± 0	8 ± 1	-5 ± 10
Δgcs1	22 ± 0	2 ± 1	5 ± 1	-43 ± 13 *
Δrav1	21 ± 0	-1 ± 1	4 ± 0	-43 ± 8 **
Δtps1	21 ± 0	-3 ± 1	5 ± 1	-32 18

The comparison of the fermentation profile of wild-type cells and of the deletion mutants was based on the concentration of ethanol produced at the end of the fermentation and on the amount of CO₂ formed at mid-fermentation point (14 h - time taken by the parental strain to reach 50% of the total CO₂ produced), as described in Methods. The results shown are means of at least two independent experiments and the statistical significance of the results obtained was quantified using a t-test (n = 2). *P < 0.05; **P < 0.01.

ISSN: 2731-3654