Biomass sources such as distillers’ grains with solubles (DGS) from first generation bioethanol production and wastewater cultivated algae provide significant supplies of feedstocks that are rich in both sugars and proteins which can be used as substrates for bio-based commodity chemicals. Here we demonstrate “one-pot” bioconversion of the protein and carbohydrate fractions of DGS and algal hydrolysates into C4 and C5 fusel alcohols using a microbial consortium incorporating two engineered Escherichia coli strains. In the engineered bioconversion system, one E. coli strain was modified for efficient conversion of hexose and pentose sugar to isobutanol; the second E. coli strain was modified for the efficient utilization of the proteins in the hydrolysates to produce mixed C4 and C5 alcohols. The inoculation ratio between the two E. coli strains in the co-culture system was optimized to obtain up to 10.3 g/L and 5.9 g/L titers of total fusel alcohols from DGS and algal hydrolysates, respectively. The bioconversion efficiency of the co-culture was found to be insignificantly different from the efficiencies of fermenting the substrates by each strain alone. Furthermore, a quantitative PCR-based cell quantification method was developed to enumerate the dynamics of each individual bacterial population in the co-culture. The results indicated that despite growth rate difference between the two strains, co-culturing didn’t compromise the growth of each strain. The q-PCR analysis also demonstrated that the fermentation with an appropriate initial inoculation ratio of the two strains is important to achieve a balanced co-culture population which results in higher total fuel titer. The E. coli co-culture strategy eliminates the need for fractionation of hydrolysates and multi-step fermentation for the conversion of multi-substrate biomass streams, significantly reducing the overall process cost and residence time.

Development of an engineered Escherichia coli consortium for bioconversion of multi-substrate biomass streams to commodity chemicals and fuels

255th National Meeting (2018)

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