Development of a production chain from vegetable biowaste to platform chemicals

Abstract

BackgroundA future bioeconomy relies on the development of technologies to convert waste into valuable compounds. We present here an attempt to design a biotechnological cascade for the conversion of vegetable waste into acetoin and electrical energy.ResultsA vegetable waste dark fermentation effluent containing mainly acetate, butyrate and propionate was oxidized in a bioelectrochemical system. The achieved average current at a constant anode potential of 0 mV against standard hydrogen electrode was 177.5 ± 52.5 µA/cm2. During this step, acetate and butyrate were removed from the effluent while propionate was the major remaining component of the total organic carbon content comprising on average 75.6%. The key players with regard to carbon oxidation and electrode reduction were revealed using amplicon sequencing and metatranscriptomic analysis. Using nanofiltration, it was possible to concentrate the propionate in the effluent. The effluent was revealed to be a suitable medium for biotechnological production strains. As a proof of principle, the propionate in the effluent of the bioelectrochemical system was converted into the platform chemical acetoin with a carbon recovery of 86%.ConclusionsTo the best of our knowledge this is the first report on a full biotechnological production chain leading from vegetable waste to the production of a single valuable platform chemical that integrates carbon elimination steps leading to the production of the valuable side product electrical energy.Electronic supplementary materialThe online version of this article (10.1186/s12934-018-0937-4) contains supplementary material, which is available to authorized users.

Electrostatic Fields Promote Methanogenesis More than Polarized Bioelectrodes in Anaerobic Reactors with Conductive Materials

“…The cyclic voltammogram (CV) for the bulk solution shows one oxidation and two reduction peaks under non-turnover conditions, similar to all anaerobic reactors (Figure a). The redox peaks of the CV indicate electrochemically active substances that include biotic and abiotic redox substances. ,,, EEB and EMA belong to the biotic redox substances, and there are several types of abiotic substances, including flavins, quinones, and humic substances. , The redox peak potentials for EEB and EMA are known to be in the range −0.20 to 0.41 V versus Ag/AgCl and −0.07 to −0.41 V versus Ag/AgCl, respectively. ,, For AC, the oxidation peak was 0.01 V versus Ag/AgCl, and there were two reduction peaks at 0.17 and −0.38 V versus Ag/AgCl. The oxidation peak and the second reduction peak appeared to be the activities of EEB and EMA, based on their reported potential ranges (Figure a).…”

“…However, Porphyromonadaceae_uc and Cloacamonas acidaminovorans were more abundant bacterial species in AC, ACPB, and ACEF than control. The family Porphyromonadaceae is an obligately anaerobic fermenter producing acetate C.…”

Enhanced production of propionic acid through acidic hydrolysis by choice of inoculum

“…Propionic acid (PA) and its salts are widely used in industries including agricultural, pharmaceutical and food as antifungal agents 1, 2 . It also can be employed as precursor for the biotechnological production of value‐added compounds, such as acetoin 3 and, thus, has been listed as an important platform chemical since the early 2000s 4 . Currently, most of the PA production around the world is by chemical synthesis through the oxidation of petrochemical raw materials such as propane or propionaldehyde 5 .…”

“…Acidic hydrolysis is an alternative method that has gained greater attention for PA production from available renewable sources, such as organic waste. It is increasingly being applied with a focus on biohydrogen production, a process known as dark fermentation, in which organic waste is utilized to generate renewable energy 3 . However, the separation of single volatile fatty acids (VFA) from complex effluents such as the fermentation broth remains a challenge, owing to the complex nature and the presence of various organics 6 .…”

“…It is increasingly being applied with a focus on biohydrogen production, a process known as dark fermentation, in which organic waste is utilized to generate renewable energy. 3 However, the separation of single volatile fatty acids (VFA) from complex effluents such as the fermentation broth remains a challenge, owing to the complex nature and the presence of various organics. 6 Techniques such as electrodialysis, 7 reactive extraction, 8 reverse osmosis, 9 nanofiltration 10 and adsorption 11 have been investigated to separate and concentrate these acids from aqueous solution and fermentation broth.…”