As a new biofuel

isobutanol has received more attentions in recent years. Because of its high tolerance to higher alcohols

Saccharomyces cerevisiae

has potential advantages as a platform microbe to produce isobutanol. In this study

we investigated integration effects of enhancing valine biosynthesis by overexpression of

ILV2

and

BAT2

with eliminating ethanol formation by deletion of

PDC6

and decreasing acetyl-CoA biosynthesis by deletion of

LPD1

on isobutanol titers. Our results showed that deletion of

LPD1

in strains overexpressing

BAT2

and

ILV2

increased isobutanol titer by 5.3-fold compared with control strain. Additional deletion of

PDC6

in

lpd1

Δ strains carrying overexpressed

BAT2

and

ILV2

further increased isobutanol titer by 1.5 fold. Overexpression of

BAT2

and

ILV2

in

lpd1

Δ strains and

pdc6

Δ strains decreased ethanol titers. Glycerol titers of the engineered strains did not have greater changes than that of control strain

while their acetic acid titers were higher

perhaps due to the imbalance of cofactors in isobutanol synthesis. Our researches suggest

that double-gene deletion of

PDC6

and

LPD1

in strains overexpressing

BAT2

and

ILV2

could increase isobutanol production dramatically than single-gene deletion of

PDC6

or

LPD1

. This study reveals the integration effects of overexpression of

ILV2

/

BAT2

and double-gene deletion of

LPD1

and

PDC6

on isobutanol production

and helps understanding future developments of engineered strains for producing isobutanol.