BackgroundThe versatility of microbial metabolic pathways enables their utilization in vast number of applications. However, the electron and carbon recovery rates, essentially constrained by limitations of cell energetics, are often too low in terms of process feasibility. Cocultivation of divergent microbial species in a single process broadens the metabolic landscape, and thus, the possibilities for more complete carbon and energy utilization.ResultsIn this study, we integrated the metabolisms of two bacteria, an obligate anaerobe Clostridium butyricum and an obligate aerobe Acinetobacter baylyi ADP1. In the process, a glucose-negative mutant of A. baylyi ADP1 first deoxidized the culture allowing C. butyricum to grow and produce hydrogen from glucose. In the next phase, ADP1 produced long chain alkyl esters (wax esters) utilizing the by-products of C. butyricum, namely acetate and butyrate. The coculture produced 24.5 ± 0.8 mmol/l hydrogen (1.7 ± 0.1 mol/mol glucose) and 28 mg/l wax esters (10.8 mg/g glucose).ConclusionsThe cocultivation of strictly anaerobic and aerobic bacteria allowed the production of both hydrogen gas and long-chain alkyl esters in a simple one-pot batch process. The study demonstrates the potential of ‘metabolic pairing’ using designed microbial consortia for more optimal electron and carbon recovery.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1186-9) contains supplementary material, which is available to authorized users.

Lignin has potential as a sustainable feedstock for microbial production of industrially relevant molecules. However, the required lignin depolymerization yields a heterogenic mixture of aromatic monomers that are challenging substrates for the microorganisms commonly used in the industry. Here, we investigated the properties of lignin-related aromatic compounds (LRAs), namely coumarate, ferulate, and caffeate, in the synthesis of biomass and products in an LRA-utilizing bacterial host Acinetobacter baylyi ADP1.The biosynthesis products, wax esters, and alkanes are relevant compounds for the chemical and fuel industries. Here, wax esters were produced by a native pathway of ADP1, whereas alkanes were produced by a synthetic pathway introduced to the host.Using individual LRAs as substrates, the growth and product formation were monitored with internal biosensors and off-line analytics. Of the tested LRAs, coumarate was the most propitious in terms of product synthesis. Wax esters were produced from coumarate with yield and titer of 37 mg/g coumarate and 202 mg/L, whereas alkanes were produced with a yield of 62.3 µg /g coumarate and titer of 152 µg/L. This study demonstrates the microbial preference for certain LRAs and highlights the potential of A. baylyi ADP1 as a host for LRA upgrading to value-added products. K E Y W O R D SAcinetobacter baylyi ADP1, alkane, lignin, wax ester

Bioprocesses involving more than one species can alleviate restrictions posed by limited substrate range of single species. Coupled, multistage cultures can be useful when heterogeneous substrates, such as lignocellulosic biomass,...

BackgroundThe versatility of microbial metabolic pathways enables their utilization in vast number of applications. However, the electron and carbon recovery rates, essentially constrained by limitations of cell energetics, are often too low in terms of process feasibility. Cocultivation of divergent microbial species in a single process broadens the metabolic landscape and thus, the possibilities for more complete carbon and energy utilization.ResultsIn this study, we integrated the metabolisms of two bacteria, an obligate anaerobe Clostridium butyricum and an obligate aerobe Acinetobacter baylyi ADP1. In the process, a glucose-negative mutant of A. baylyi ADP1 first deoxidized the culture allowing C. butyricum to grow and produce hydrogen from glucose. In the next phase, ADP1 produced long chain alkyl esters utilizing the by-products of C. butyricum, namely acetate and butyrate.ConclusionsThe cocultivation of strictly anaerobic and aerobic bacteria allowed the production of both hydrogen gas and long-chain alkyl esters in a simple one-pot batch process. The study demonstrates the potential of ‘metabolic pairing’ using designed microbial consortia for optimal electron and carbon recovery.

The pulp and paper industry together with lignocellulosic biofuel production provides plentiful streams of lignin and lignin-derived molecules (LDMs) that currently remain underutilized. The heterogeneity and complexity of lignin along with the lack of convenient tools significantly hamper its utilization. Selective separation of these LDMs from streams using specific tools would allow the recovery of aromatic compounds, as well as facilitate biological processes aiming at lignin valorization. To this end, here we report the isolation and characterization of single-chain variable fragment (scFv) antibodies against ferulate, coumarate, and caffeate, which are the molecular representatives of LDMs. Binders for the target LDMs were enriched by interrogating a synthetic scFv library with the phage display technique. As a result, scFv binders specific against each of the target molecules were obtained with affinities in the micromolar range. The selectivity of scFvs towards specific LDMs was proved by recovering caffeate from simulated LDM solution, Kraft lignin, and rice straw hydrolysate samples. Further proof of concept studies with model compounds demonstrated the applicability of antibody-based binders as a detection tool for monitoring microbial LDM conversion. Overall, this study demonstrates the potential of scFv binders as a specific toolset for lignin compound recovery and analysis.

Lignin has potential as a sustainable feedstock for microbial production of industrially relevant molecules. However, the required lignin depolymerization yields a heterogenic mixture of aromatic monomers that are challenging substrates for the microorganisms commonly used in industry. Here, we investigated the properties of lignin-derived molecules (LDMs), namely coumarate, ferulate, and caffeate, in the synthesis of biomass and products in a LDM-utilizing bacterial host Acinetobacter baylyi ADP1. The biosynthesis products, wax esters and alkanes, are relevant compounds for the chemical and fuel industries. In A. baylyi ADP1, wax esters are produced by a native pathway, whereas alkanes are produced by a synthetic pathway introduced to the host. Using individual LDMs as substrates, the growth, product formation, and toxicity to cells were monitored with internal biosensors. Of the tested LDMs, coumarate was the most propitious in terms of product synthesis. Wax esters were produced from coumarate with a yield and titer of 40 mg /gcoumarate and 221 mg/L, whereas alkanes were produced with a yield of 62.3 μg /gcoumarate and titer of 152 μg/L. This study demonstrates the microbial preference for certain LDMs, and highlights the potential of A. baylyi ADP1 as a convenient host for LDM upgrading to value-added products.