Abstract

Metabolic Profiling of Geobacter Sulfurreducens During a Scale-up Process

Howbeer Muhamadali, Research Associate, University of Manchester

Geobacter species are a fascinating group of microorganisms which have the ability of coupling the oxidation of organic compounds to the reduction of insoluble metal contaminants, such as Fe(III) and Mn(IV). This has led to the development of a growing number of strategies and applications in different fields ranging from bioremediation, biotechnology, bioelectronics and the evolving field of electromicrobiology. The process of bio-magnetite nanoparticle production using G. sulfurreducens and its wide-range of applications have seen increasing interest during the past decade. However, the end product quantities of such bio-processes can be said to be limited, and the successful commercialization of these processes is dependent on the ability to generate large quantities of products cost-effectively. Here, we scale-up this batch culture bioprocess from 100 mL serum bottles to 5 L bioreactor, which resulted an extended lag phase of ~18 h. This alteration in growth behaviour was further investigated at 13 distinct time points during the incubation period via metabolic fingerprinting and profiling techniques, to determine the metabolic response of cells to the scale-up process. Fourier transform infrared (FT-IR) spectroscopy results confirmed the occurrence of an extended lag phase for cells grown in the 5 L bioreactor, whilst principal components-discriminant function analysis (PC-DFA) of FT-IR spectra revealed growth phase-specific clustering patterns suggesting variation in concentration and distribution of different biochemical components of the cells. Metabolic profiles of both sets of the cell extracts were acquired by gas chromatography-mass spectrometry (GC-MS). GC MS results showed an overall accumulation of fumarate during the lag-phase in both culturing conditions, coinciding with the detected concentrations of oxaloacetate, pyruvate, nicotinamide and glycerol-3-phosphate being at their lowest levels compared to other growth phases. These metabolites were ove