Selectivity and Sustainability of Electroenzymatic Process for Glucose Conversion to Gluconic Acid

Abstract

Electroenzymatic processes are interesting solutions for the development of new processes based on renewable feedstocks, renewable energies, and green catalysts. High-selectivity and sustainability of these processes are usually assumed. In this contribution, these two aspects were studied in more detail. In a membrane-less electroenzymatic reactor, 97% product selectivity at 80% glucose conversion to gluconic acid was determined. With the help of nuclear magnetic resonance spectroscopy, two main side products were identified. The yields of D-arabinose and formic acid can be controlled by the flow rate and the electroenzymatic reactor mode of operation (fuel cell or ion-pumping). The possible pathways for the side product formation have been discussed. The electroenzymatic cathode was found to be responsible for a decrease in selectivity. The choice of the enzymatic catalyst on the cathode side led to 100% selectivity of gluconic acid at somewhat reduced conversion. Furthermore, sustainability of the electroenzymatic process is estimated based on several sustainability indicators. Although some indicators (like Space Time Yield) are favorable for electroenzymatic process, the E-factor of electroenzymatic process has to improve significantly in order to compete with the fermentation process. This can be achieved by an increase of a cycle time and/or enzyme utilization which is currently low.

Quantitative and Non‐Quantitative Assessments of Enzymatic Electrosynthesis: A Case Study of Parameter Requirements

“…With the help of nuclear magnetic resonance (NMR) spectroscopy, a product selectivity of 97 % was reported. Additionally, glucose conversion of 80 % and E‐factor of 9 were obtained [22] . A further distinctive result of the application of an electroenzymatic process was reported by Sokol et al.…”

“…The amount of waste is difficult to quantify, we recommend excluding water and normalize the waste generation to the reactor volume [21,22] …”

“…E À factor Environmental factor E À factor ¼ c waste =c p Ratio of waste to product The amount of waste is difficult to quantify, we recommend excluding water and normalize the waste generation to the reactor volume [21,22] c p ; c s Product titer and substrate loading…”

Process Intensification as Game Changer in Enzyme Catalysis

“…Computational methods such as design of experiments (Tosstorff et al, 2017) or modelling in combination with simulations (Bormann et al, 2021) appear to be particularly useful for an accelerated implementation of electroenzymatic processes in industry. Furthermore, sustainability of the electroenzymatic process should be evaluated (Varničić, 2020).…”

Mini-Review: Recent Technologies of Electrode and System in the Enzymatic Biofuel Cell (EBFC)

“…Therefore, the need to analyze the product resulting in the reaction at the EBFC electrode is needed. Varničić et al [84] produced membrane-less EBFCs and used nuclear magnetic resonance spectroscopy to determine the production of two main products: D-arabinose and formic acid. The authors found that the production of this product was influenced by the enzyme selection on the cathode side of EBFC.…”