Engineering microbes for tolerance to next-generation biofuels

Table 1 Toxicity levels for next-generation biofuels

	Tolerance (% v/v)	Microorganism	Reference
Biogasolines
Butanol	1.5%	Escherichia coli	[1]
	1.5%	Zymomonas mobilis	[1]
	1.5%	Pseudomonas putida	[17]
	1.6%	Clostridium acetobutylicum	[55]
	2.0%	Saccharomyces cerevisiae	[1]
2-Methyl-1-butanol (2MB)	0.1%	Escherichia coli	[70]
3-Methyl-1-butanol (3MB)	0.1%	Escherichia coli	[71]
Geraniol	0.05%	Escherichia coli	[7]
1-Propanol	5.0%	Escherichia coli	[28]
Biodiesels
Farnesyl hexanoate	1.0%^a	Escherichia coli	[7]
Geranyl acetate	0.5%^a	Escherichia coli	[7]
Bioaviation fuels
Pinene	0.5%^a	Escherichia coli	[7]
Limonene	0.025%	Escherichia coli	[7]

^aBiofuel is inhibitory, but not lethal; percentages listed are where growth drops to 75% of the normal, unstressed levels.