(568c) Microbial Utilization of Aqueous Co-Products From Hydrothermal Liquefaction of Microalgae Nannochloropsis Oculata

Hydrothermal liquefaction of biomass is a promising technology for producing sustainable biofuels and research is underway at the University of Michigan looking at its potential usage with algal feedstocks. While the technology produces an oily “biocrude” product very similar to crude petroleum, there is also an aqueous co-product formed that still contains a large fraction of the initial algae feedstock’s carbon, nitrogen, and phosphorus compounds, along with other nutrients. Effective utilization of this aqueous algae co-product (AqAl) will have a large impact on the efficiency of the overall fuel generation process, yet initial research shows this may be challenging due to its complex chemical makeup and apparent toxicity to algae.

This work proposes a microbial culture side-process as a way to reform biomass from the organic carbon in AqAl for further fuel production and detoxify remaining AqAl to facilitate recycle of fertilizer compounds back to an algae growth operation. Model bacteria Escherichia coli and Pseudomonas putida were cultured in growth media containing AqAl as the sole carbon, nitrogen, and phosphorus source and shown to withstand AqAl concentrations higher than in previously published studies that attempted to regrow algae on AqAl.

These microbes were then developed in a long-term adaptive evolution study in order to improve their AqAl utilization and tolerance phenotypes. Bacterial cultures were grown continuously over several hundred generations in media of increasing AqAl concentration such that random mutagenesis and natural selection enriched the cultures in mutants with improved fitness. Strains with improved AqAl tolerance and/or utilization characteristics were isolated, genetically sequenced, and compared to parent strains in order to elucidate the genetic basis of phenotypic improvements.

This presentation will focus on the results of the initial culturability tests, the improved properties of the strains derived via evolution, and the effects these organisms may have on a consolidated algae biofuel process.  

This work was funded, in part, by the NSF (EFRI 0937992), a fellowship Michael Nelson received from the Cellular Biotechnology Training Program at U of M, and a USDA NIFA pre-doctoral fellowship.