Isoprene synthase variants for improved microbial production of isoprene

An isolated host cell comprising a heterologous polynucleotide sequence encoding a truncated isoprene synthase variant in operable combination with a promoter, wherein said truncated isoprene synthase variant comprises one or more amino acid substitution(s) at one or more amino acid residues corresponding to a poplar isoprene synthase having the sequence of SEQ ID NO:

• 120, wherein said substitution(s) are selected from the group consisting of V10M, F12S, T15A, E18G, V58I, V58F, L70Q, L70R, L70V, L70T, T71P, V79L, E89D, G94A, S119F, F120L, G127R, E175V, T212I, S257A, R262G, A266G, F280L, N297K, F305L, L319M, E323K, A328T, D342E, A359T, K366N, E368D, L374M, S396T, V418S, K438N, H440R, T442A, I449V, A469S, K500R, K505Q, G507S, S509N, F511Y, and N532K;
• and
• wherein the variant is capable of more effectively converting dimethylallyl diphosphate (DMAPP) to isoprene, as compared to an isoprene synthase variant without a substitution.