Microbial communities comprised of phototrophs and heterotrophs hold great promise for sustainable biotechnology. Successful application of these communities relies on the selection of appropriate partners. Here we construct four community metabolic models to guide strain selection, pairing phototrophic, sucrose-secreting Synechococcus elongatus with heterotrophic Escherichia coli K-12, Escherichia coli W, Yarrowia lipolytica, or Bacillus subtilis. Model simulations reveae metabolic exchanges that sustain the heterotrophs in minimal media devoid of any organic carbon source, pointing to S. elongatus-E. coli K-12 as the most active community. Experimental validation of flux predictions for this pair confirms metabolic interactions and potential production capabilities. Synthetic communities bypass memberspecific metabolic bottlenecks (e.g. histidine-and transport-related reactions) and compensate for lethal genetic traits, achieving up to 27% recovery from lethal knockouts. The study provides a robust modelling framework for the rational design of synthetic communities with optimized growth sustainability using phototrophic partners.
BackgroundTo overcome the daunting technical and economic barriers of algal biofuels, we evaluated whether seawater can be a viable medium for economically producing filamentous Spirulina subsalsa as feedstock, using monosodium glutamate residue (MSGR) produced by the glutamate extraction process as an inexpensive nutrient source.ResultsSpirulina subsalsa cannot grow in pure seawater, but exhibited faster biomass accumulation in seawater supplemented with MSGR than in freshwater medium (modified Zarrouk medium). Introducing seawater into media ensured this cyanobacterium obtained high lipid productivity (120 mg/L/day) and suffered limited bacterial infections during growth. Moreover, the yields of protein, carotenoids and phytols were also improved in seawater mixed with MSGR. S. subsalsa exhibited high biomass and lipid productivity in bag bioreactors with 5- and 10-L medium, demonstrating the potential of this cultivation method for scaling up. Moreover, seawater can produce more biomass through medium reuse. Reused seawater medium yielded 72% of lipid content compared to pristine medium. The reason that S. subsalsa grew well in seawater with MSGR is its proficient adaptation to salinity, which included elongation and desaturation of fatty acids, accumulation of lysine and methionine, and secretion of sodium. The nutrients provided by MSGR, like organic materials, played an important role in these responses.ConclusionSpirulina subsalsa has an efficient system to adapt to saline ambiance in seawater. When supplemented with MSGR, seawater is a great potential medium to produce S. subsalsa in large scale as biofuel feedstock. Meanwhile, value-added products can be derived from the ample protein and pigments that can broaden the range of biomass application and improve this biorefinery economics.Electronic supplementary materialThe online version of this article (10.1186/s13068-019-1391-1) contains supplementary material, which is available to authorized users.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.