12-08: Hydrocarbons from cyanobacteria: a survey of a novel source of biofuel production

Cyanobacteria possess the ability to produce hydrocarbons directly from fatty acids, which presents an opportunity to by-pass the costly and energy intensive conversion steps required for fuels from triglyceride based feedstocks. A survey of cyanobacterial hydrocarbons was undertaken with the goal of gaining a deeper understanding of the composition of hydrocarbons produced by cyanobacteria and the underlying biosynthetic processes involved with their production. This study selected twenty five cyanobacterial strains with a broad phylogenetic sampling of each of the major cyanobacterial subdivisions. The survey results indicate that all of the cyanobacteria sampled produce hydrocarbons suggesting that hydrocarbon production is a ubiquitous phenomenon among cyanobacteria. Additionally, the composition of hydrocarbons produced by cyanobacteria varies considerably with a range of chain lengths, branching patterns and double bond positions. These hydrocarbons derive from pathways that both use fatty acid precursors. However, there are multiple structural features of the observed hydrocarbons that indicate a variety of novel modifications to fatty acid precursors or resulting hydrocarbon including unique positions for double bonds and methyl groups suggesting the possible involvement of a unique desaturase or isomerase in the case of the observed alkenes and a unique methyltransferase for branched hydrocarbons. This information can be used to identify novel enzymes involved in cyanobacterial hydrocarbon biosynthesis and subsequently engineer strains with a capacity for enhanced quantity and quality of biofuel production.