Toward a Hybrid Biosensor System for Analysis of Organic and Volatile Fatty Acids in Fermentation Processes.

Désirée L. Röhlen,Michael Keusgen,Markus Dahmen,Johanna Pilas,Thorsten Selmer,Michael J. Schöning

doi:10.3389/fchem.2018.00284

Désirée L. Röhlen, Michael Keusgen + Show 4 more

Open Access

https://doi.org/10.3389/fchem.2018.00284

Copy DOI

Abstract

Monitoring of organic acids (OA) and volatile fatty acids (VFA) is crucial for the control of anaerobic digestion. In case of unstable process conditions, an accumulation of these intermediates occurs. In the present work, two different enzyme-based biosensor arrays are combined and presented for facile electrochemical determination of several process-relevant analytes. Each biosensor utilizes a platinum sensor chip (14 × 14 mm2) with five individual working electrodes. The OA biosensor enables simultaneous measurement of ethanol, formate, d- and l-lactate, based on a bi-enzymatic detection principle. The second VFA biosensor provides an amperometric platform for quantification of acetate and propionate, mediated by oxidation of hydrogen peroxide. The cross-sensitivity of both biosensors toward potential interferents, typically present in fermentation samples, was investigated. The potential for practical application in complex media was successfully demonstrated in spiked sludge samples collected from three different biogas plants. Thereby, the results obtained by both of the biosensors were in good agreement to the applied reference measurements by photometry and gas chromatography, respectively. The proposed hybrid biosensor system was also used for long-term monitoring of a lab-scale biogas reactor (0.01 m3) for a period of 2 months. In combination with typically monitored parameters, such as gas quality, pH and FOS/TAC (volatile organic acids/total anorganic carbonate), the amperometric measurements of OA and VFA concentration could enhance the understanding of ongoing fermentation processes.

Highlights

In light of the depletion of fossil fuels, the public interest of biogas production from renewable resources is steadily increasing
For construction of the biosensors and realization of photometric assays, the following enzymes were used: Acetate kinase from Escherichia coli (AK, 150 U mg−1), alcohol dehydrogenase from Saccharomyces cerevisiae (ADH, 310 U mg−1), citrate synthase from porcine heart (CS, 100 U mg−1), diaphorase from Clostridium kluyveri (DIA, 51 U mg−1), formate dehydrogenase from Candida boidinii (FDH, 0.49 U mg−1), D-lactate dehydrogenase from Lactobacillus leichmanii (DLDH, 213 U mg−1), L-lactate dehydrogenase from Bacillus stearothermophilus (L-LDH, 174.5 U mg−1) and pyruvate kinase from rabbit muscle (PK, 1,000 U mg−1) were each obtained from Sigma-Aldrich
Nowadays, monitoring of organic and volatile fatty acids in anaerobic fermentation processes is only feasible by laborious techniques, such as HPLC or GC

Summary

Introduction

In light of the depletion of fossil fuels, the public interest of biogas production from renewable resources is steadily increasing. In order to realize the potential of the growing market, several technological and Hybrid Biosensor for Fermentation Processes economic aspects need to be improved to ensure process stability and efficient methane (CH4) production. Some of these important factors comprise appropriate biogas purification technologies, a suitable feedstock composition and ideal conditions inside the biogas reactor (Weiland, 2010; Andriani et al, 2014; Achinas et al, 2017). In order to overcome this problem, biosensors have been developed as reliable tools for fast and accurate analysis of several compounds

Methods

Results

Conclusion