Statistical optimization of waste molasses-based exopolysaccharides and self-sustainable bioelectricity production for dual chamber microbial fuel cell by Bacillus piscis

Abstract

Background The application of exopolysaccharide-producing bacteria (EPS) in dual chamber microbial fuel cells (DCMFC) is critical which can minimize the chemical oxygen demand (COD) of molasses with bioelectricity production. Hence, our study aimed to evaluate the EPS production by the novel strain Bacillus piscis by using molasses waste. Therefore, statistical modeling was used to optimize the EPS production. Its structure was characterized by UV, FTIR, NMR, and monosaccharides compositions. Eventually, to highlight B. piscis' adaptability in energy applications, bioelectricity production by this organism was studied in the BCMFC fed by an optimized molasses medium. Results B. piscis OK324045 characterized by 16S rRNA is a potent EPS-forming organism and yielded a 6.42-fold increase upon supplementation of molasses (5%), MgSO4 (0.05%), and inoculum size (4%). The novel exopolysaccharide produced by Bacillus sp. (EPS-BP5M) was confirmed by the structural analysis. The findings indicated that the MFC's maximum close circuit voltage (CCV) was 265 mV. The strain enhanced the performance of DCMFC achieving maximum power density (PD) of 31.98 mW m−2, COD removal rate of 90.91%, and color removal of 27.68%. Furthermore, cyclic voltammetry (CV) revealed that anodic biofilms may directly transfer electrons to anodes without the use of external redox mediators. Additionally, CV measurements made at various sweep scan rates to evaluate the kinetic studies showed that the electron charge transfer was irreversible. The SEM images showed the biofilm growth distributed over the electrode’s surface. Conclusions This study offers a novel B. piscis strain for EPS-BP5M production, COD removal, decolorization, and electricity generation of the optimized molasses medium in MFCs. The biosynthesis of EPS-BP5M by a Bacillus piscis strain and its electrochemical activity has never been documented before. The approach adopted will provide significant benefits to sugar industries by generating bioelectricity using molasses as fuel and providing a viable way to improve molasses wastewater treatment.

Reduction of Toxic Metal Ions and Production of Bioelectricity through Microbial Fuel Cells Using Bacillus marisflavi as a Biocatalyst

“…The initial voltage values were practically equal, being 0.056 and 0.042 V in the MFC-SC with Bacillus marisflavi and the MFC-Target, respectively; these values increased until the sixth day, where the MFC-Bacillus marisflavi (0.798 V) showed a 58.62% higher voltage than the MFC-Target (0.3305 V), as shown in Figure 1a. This phenomenon of increasing and decreasing voltage values was also observed by Sakr et al (2023), who used Bacillus piscis as a biocatalyst in their MFCs and mentioned that use life of their wastewater limited the potential of each MFC. This potential can be regenerated by introducing a new substrate [26,27].…”

“…This phenomenon of increasing and decreasing voltage values was also observed by Sakr et al (2023), who used Bacillus piscis as a biocatalyst in their MFCs and mentioned that use life of their wastewater limited the potential of each MFC. This potential can be regenerated by introducing a new substrate [ 26 , 27 ]. The same phenomenon was also observed by Ren et al (2021) who used Saccharomyces cerevisiae and Pseudomonas aeruginosa ; the potential generated was limited by the redox processes originating in the chambers of the MFCs, which, due to not having more useful substances for realization after this process, began to show decreasing values [ 28 ].…”