# A Novel Agro‐Waste Formulated Medium Enhanced the Growth of Electrogenic Enterobacter Species Isolated Using Microbial Fuel Cell System: Response Surface Methodology Approach

## TL;DR

This study identifies and optimizes the growth of an electrogenic Enterobacter species using agro-waste, showing potential for cost-effective microbial fuel cell applications.

## Contribution

The first study to use 16S rRNA gene sequencing from anode biofilm to identify native Enterobacter species for MFC applications.

## Key findings

- Barley bran formulated media achieved maximum cell growth with OD600nm of 1.52167 and CDW of 0.01541 g/L.
- RSM optimization increased cell growth yield by 32.3% compared to unoptimized conditions.
- The isolate showed tolerance to a wide range of temperatures, pH levels, and high salt concentrations.

## Abstract

Our study aims to identify electrogenic bacteria and optimise culture conditions using different commercial and agro‐industrial wastes as a sole carbon source. Potential candidates of electrogenic bacteria isolates (EBIs) were screened from anode‐developed biofilm in a double‐chambered microbial fuel cell (MFC) bioreactor system. Characterisation using cyclic voltammetry (CV) showed that the isolated bacteria had a potential bio‐electrochemical property. Statistical techniques were used, including response surface methodology (RSM) with a central composite design (CCD). The highest cell growth, measured by optical density at 600 nm (OD600nm) (1.1407 ± 0.00316) and cell dry weight (CDW) (0.02135 ± 0.00152 g/L), was obtained when commercial carbon glucose was used. Cost‐effective, barley bran formulated media resulted in maximum growth, OD600nm 1.52167 ± 0.03476 and CDW with 0.01541 ± 0.000071 g/L. The RSM optimised condition achieved a 32.3% fold increase of cell growth yield (OD600nm) compared to unoptimised conditions. This is the first study to use 16S rRNA gene sequencing from anode biofilm to identify native Enterobacter species. In conclusion, the recently discovered isolate exhibited growth conditions between 18°C and 52°C, pH 3 and pH 11, and resistance to high salt concentrations (0.332 M NaCl). It might therefore be considered a potentially versatile biocatalyst candidate for MFC applications.

Electrogenic isolate, Enterobacter sp. DSAAI‐4 exhibited broad substrate range utilisation ability and high salt tolerance. Use of agro‐industrial waste barley bran for culture growth was promising and low cost.