Evaluating nitrogen sources for enhanced halophilic bacteria growth, electron transfer, and microbial fuel cell performance

Abstract

This study investigates the comparative effects of different nitrogen sources—peptone, tryptone, and bovine serum albumin (BSA)—on the growth, electron transport mechanisms, and MFCs performance of halophilic bacteria Bacillus clausii J1G-o%B. The objective is to identify the most effective nitrogen source for optimizing bacterial growth and enhancing MFC efficiency. Comprehensive analysis reveals that tryptone and peptone significantly enhance bacterial growth and stability compared to BSA. Increased concentrations of these nitrogen sources correlate with elevated ammonia production and notable pH changes, indicating heightened metabolic activity. The non-linear relationship between scan rate and current density suggests diffusion-limited redox reactions. Notably, higher tryptone concentrations significantly increase the electron transfer rate constant to 3.66 ± 0.02 s⁻¹ when the concentration increases to 0.1 g/100 mL. Early voltage increases at around the 30th hour to 0.175 V under the T-0.1 condition further support the critical role of tryptone in accelerating bacterial growth and biofilm formation. Cyclic voltammetry experiments demonstrate that nitrogen source type and concentration influence electrical double layer characteristics. These findings underscore the potential of tryptone to optimize Bacillus clausii electrochemical performance, achieving a maximum power density of 36.93 mW/m² at a current density of 196 mA/m², paving the way for bioelectrochemical system applications.