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Background  First generation bioethanol production utilizes the starch fraction of maize, which accounts for approximately 60% of the ash-free dry weight of the grain. Scale-up of this technology for fuels applications has resulted in a massive supply of distillers’ grains with solubles (DGS) coproduct, which is rich in cellulosic polysaccharides and protein. It was surmised that DGS would be rapidly adopted for animal feed applications, however, this has not been observed based on inconsistency of the product stream and other logistics-related risks, especially toxigenic contaminants. Therefore, efficient valorization of DGS for production of petroleum displacing products will significantly improve the techno-economic feasibility and net energy return of the established starch bioethanol process. In this study, we demonstrate ‘one-pot’ bioconversion of the protein and carbohydrate fractions of a DGS hydrolysate into C4 and C5 fusel alcohols through development of a microbial consortium incorporating two engineered  Escherichia coli  biocatalyst strains.    Results  The carbohydrate conversion strain  E. coli  BLF2 was constructed from the wild type  E. coli  strain B and showed improved capability to produce fusel alcohols from hexose and pentose sugars. Up to 12 g/L fusel alcohols was produced from glucose or xylose synthetic medium by  E. coli  BLF2. The second strain,  E. coli  AY3, was dedicated for utilization of proteins in the hydrolysates to produce mixed C4 and C5 alcohols. To maximize conversion yield by the co-culture, the inoculation ratio between the two strains was optimized. The co-culture with an inoculation ratio of 1:1.5 of  E. coli  BLF2 and AY3 achieved the highest total fusel alcohol titer of up to 10.3 g/L from DGS hydrolysates. The engineered  E. coli  co-culture system was shown to be similarly applicable for biofuel production from other biomass sources, including algae hydrolysates. Furthermore, the co-culture population dynamics revealed by quantitative PCR analysis indicated that despite the growth rate difference between the two strains, co-culturing didn’t compromise the growth of each strain. The q-PCR analysis also demonstrated that fermentation with an appropriate initial inoculation ratio of the two strains was important to achieve a balanced co-culture population which resulted in higher total fuel titer.    Conclusions  The efficient conversion of DGS hydrolysates into fusel alcohols will significantly improve the feasibility of the first generation bioethanol process. The integrated carbohydrate and protein conversion platform developed here is applicable for the bioconversion of a variety of biomass feedstocks rich in sugars and proteins.    Electronic supplementary material  The online version of this article (10.1186/s12934-017-0804-8) contains supplementary material, which is available to authorized users.

Bioconversion of distillers’ grains hydrolysates to advanced biofuels by an Escherichia coli co-culture