Biofuels, Bioenergy & Bioeconomy

Statement of the Problem: Due to increased productivities and cultivation in marginal lands, microalgae have great potential as feedstock for biofuels alternative to plant crops. However, the current cost of producing biofuels from microalgae biomass is still high to envision massive and profitable commercialization in the near future. It is presumed that obtaining other higher-value byproducts in biorefineries would increase the profitability. Among other aspects, access to renewables as well as recycling of nutrients as substitutes for conventional fertilizers would be mandatory.

Methodology & Theoretical Orientation: We have been proposing alternative multispecies microbial cells-factories for the production of biofuels. Basically, the concept proposes the integration of operations that are exceptionally well performed by single microorganisms (whether naturally occurring or after genetic optimization) into multispecies systems than can execute more complex tasks and/or outperform any single species. We attempt to increase the use of N₂ from the air as a sole source of N-fertilizer for microalgae.

Findings: We used a N₂-fixing cyanobacterium that produces N-rich biomass that could be efficiently converted into biomass of a variety of microalgae. When using oleaginous strains, on-farm oil-production potential yields by ePBR simulations were up to 20-fold higher than those reported for soy oil. On the other hand, when we used microalgae accumulating carbohydrates (60-70% w/w), after a mild acid treatment for biomass hydrolysis and saccharification, bioethanol was produced at nearly 90% of its theoretical yield by fermentation with yeasts. The system also produced protein-rich biomass fractions as potential feed supplement and allowed some recycling of nutrients.

Conclusion & Significance: We have provided strong proof-of-principle suggesting potential for the economic and environmentally sustainable production of biofuels in multispecies biorefineries. Both on-farm demonstration and detailed modeling of environmental performance are required to take these ideas to a next step.