Copper-induced exopolysaccharide production by Lelliottia amnigena strain LABEM

Abstract

Exopolysaccharide (EPS) prodcution is a general mechanism employed by bacteria to thrive under stressful conditions. We report an increase in the production of EPS by Lelliottia amnigena strain LABEM through CuSO4 exposure along with the use of low-cost carbon sources, namely sucrose (SUC) and crude glycerin (CG). The production of EPS was analyzed in relation to yield, and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and thermogravimetric analysis. L. amnigena grew in up to 1.0 mM CuSO4, with a maximum EPS yield of 51.8% at 0.6 mM CuSO4. The absence of copper detection in the enhanced EPS batches is innovative, indicating a potential reduction in purification steps and heavy metal removal from the produced EPS. This suggests a possible low copper affinity of the produced EPS until the production of 0.8 mM CuSO4. Microbial supplementation with CuSO4 also enhanced EPS thermostability and surface roughness, showcasing intriguing properties applicable to drilling fluids and pharmaceutical uses. High-performance liquid chromatography (HPLC) and FTIR showed the polysaccharide nature of the products and the presence of the highly valuable EPS constituent fucose. The results illustrate the relationship between exopolysaccharide and heavy metal exposure, with a focus on enhancing bioprocesses. This expands our understanding and applications beyond heavy metal adsorption and removal. EPS properties and composition suggest diverse applications, such as food additives and in other processes that employ fucose polymer. Future experiments should explore the various applications of this exopolysaccharide and the scale-up of the technology.