Recombinant yeasts bioengineered to overexpress genes for utilization of fatty acids to produce acetone and isopropanol, and methods of use thereof. The yeasts are modified to express, constitutively express, or overexpress an acetyl-CoA thioesterase, an acetyl-CoA C-acetyltransferase, an acetoacetyl-CoA transferase, an acetoacetyl-CoA thioesterase, an acetoacetate decarboxylase, an isopropanol dehydrogenase, or any combination thereof. The methods include cultivating the recombinant yeasts to convert any fatty acid-containing feedstocks into acetone and/or isopropanol.

The present invention provides for a polyketide synthase (PKS) capable of synthesizing a 3-hydroxycarboxylic acid or ketone. The present invention also provides for a host cell comprising the PKS and when cultured produces the 3-hydroxycarboxylic acid or ketone.

Described are methods for the production of isobutene comprising the enzymatic conversion of 3-methylcrotonic acid into isobutene wherein said 3-methylcrotonic acid is obtained by the enzymatic conversion of 3-methylcrotonyl-CoA into 3-methylcrotonic acid or wherein said 3-methylcrotonic acid is obtained by the enzymatic conversion of 3-hydroxyisovalerate (HIV) into 3-methylcrotonic acid. It is described that the enzymatic conversion of 3-methylcrotonic acid into isobutene can, e.g., be achieved by making use of a 3-methylcrotonic acid decarboxylase, preferably an FMN-dependent decarboxylase associated with an FMN prenyl transferase, an aconitate decarboxylase (EC 4.1.1.6), a methylcrotonyl-CoA carboxylase (EC 6.4.1.4), or a geranoyl-CoA carboxylase (EC 6.4.1.5).

Recombinant microorganisms are provided which have been engineered to produce fatty alcohols. Also provided are recombinant microorganisms which comprise a heterologous polynucleotide encoding a fatty alcohol reductase enzyme and an introduced polynucleotide encoding a -ketoacyl acyl carrier protein synthase.

Described are acyl-CoA hydrolase (ACH) variants variants showing an improved activity in converting 3-methylcrotonyl-CoA into 3-methylcrotonic acid or an increased activity in converting crotonyl-CoA into crotonic acid as well as methods for the production of 3-methylcrotonic acid or isobutene or crotonic acid using such enzyme variants.