Developing Streptomyces venezualae as a platform organism for production of branched fuel compounds

Biosynthesis of branched hydrocarbon chains is a critical step towards development of biofuels with tunable properties, including high octane ratings and low freezing points. To achieve production of branched hydrocarbons JBEI will employ polyketide synthases (PKSs). Engineering of PKS pathways favors a native host; this work therefore focuses on Streptomyces venezualae ATCC 11702 as a model strain. While S. venezualae is well characterized for industrial production of antibiotics, its viability as a platform organism for large-scale biofuel production is unknown. At the ABPDU, we conducted shake flask and 2L-scale fermentation studies to understand growth patterns of S. venezualae on cellulosic hydrolysates. Early results demonstrate growth of S. venezualae on corn stover hydrolysate up to a dry cell weight of 9g/L upon consumption of cellulosic sugars. Inhibitory effects of hydrolysate were observed during fermentation; these effects reduced biomass yield and were partially mitigated by shifting the fermentation strategy to fed-batch, enabling more gradual detoxification of inhibitory compounds. Further research will focus on overcoming inhibitory effects via fermentation process development and optimization of the biomass pretreatment process, enabling fermentation with rapid growth rates and high yields. Ultimately, we seek to develop S. venezualae as a microbial chassis for efficient conversion of cellulosic hydrolysates into highly branched fuel compounds suitable for both spark ignition and compression ignition engines.