Details Emerge On Alkane Biosynthesis

Scientists at biotechnology firm LS9, based in South San Francisco, have pinpointed the genes and enzymes that certain bacteria use to convert intermediates of fatty acid metabolism to alkanes and alkenes (Science 2010, 329, 559). Discovery of these previously elusive genes and the enzymes they express provides a better understanding of the alkane biosynthetic pathway and should aid scale-up of microbial production of biofuels and chemicals. Bacteria build fatty acid chains using fatty acid synthase and other enzymes to add hydrocarbon units to an acyl moiety attached to acyl carrier protein (ACP). LS9’s commercial technology involves genetic alterations of the industrial workhorse bacterium Escherichia coli that selectively divert the end product of this biosynthesis, fatty acyl ACP, to alkanes, al­kenes, fatty alcohols, or fatty esters that are secreted by the bacterial cells (C&EN, June 28, page 9). LS9’s Andreas Schirmer and coworkers describe a genomic analysis of cyanobacteria leading to identification of two genes responsible for alkane biosynthesis. When the recombinant genes encoding acyl ACP reductase and aldehyde decarbonylase enzymes were overexpressed, E. coli produced C₁₃ to C₁₇ alkanes and alkenes.