Online monitoring of yeast cultivation using a fuel-cell-type activity sensor

Abstract

A microbial fuel-cell type activity sensor integrated into 500 mL and 3.2 L bioreactors was employed for ampero-(lA) and potentiometric (mV) measurements. The aim was to follow the microbial activity during ethanol production by Saccharomyces cerevisiae and to detect the end of carbohydrate consumption. Three different sensor setups were tested to record electrochemical signals produced by the metabolism of glucose and fructose (1:1) online. In a first setup, a reference electrode was used to record the potentiometric values, which rose from 0.26 to 0.5 V in about 10 h during the growth phase. In a second setup, a combination of ampero-and pseudo-potentiometric measurements delivered a maximum voltage of 35 mV. In this arrangement, the pseudo-potentiometric signal changed in a manner that was directly proportional to the amperometric signals, which reached a maximum value of 32 lA. In a third type of arrangement, a reference electrode was added to the anodic bioreactor compartment to carry out ampero-and potentiometric measurements; this is made possible by the high internal resistance of the cultivation. In this case, the reference potential rose to 0.44 V while the current maximum recorded by the working electrodes reached 27 lA. Reference and pseudo-reference electrodes were in all cases K 3 Fe(CN) 6 /carbon. Electrodes were made of 9 cm 2 woven graphite. To compare the electrochemical signals with established values, the metabolism was also monitored for optical density (at 600 nm) indicating biomass production. For fructose and glucose conversion, HPLC with an Aminex column and RI detector was used, and ethanol production was analyzed by GC with methanol as internal standard. The combination of amperometric and potentiometric recordings was found to be an ideal setup and was successfully used in reproducible cultivations.

Outward electron transfer by Saccharomyces cerevisiae monitored with a bi‐cathodic microbial fuel cell‐type activity sensor

“…To test the influence of the mediator properties of the peptone soy media used on electron transfer through the culture medium, compared to direct electron transfer from the yeast cells to the anode, a bi‐cathodic microbial fuel cell type biosensor was constructed (Figure 2b). The base was a 500 ml MFC with two cathodes on opposite sides (Favre et al , 2009). The anodic compartment in between was separated into two anodic chambers (500 and 10 cm 3 ) by a dialysis membrane (MWCO 12 000–14 000).…”

Apparent diameter and cell density of yeast strains with different ploidy

“…To maintain linearity between the c and OD 600 values, the measured OD 600 values must be within the dynamic range of equipment. However, the values frequently reach to 10 at the end of cultivation in the actual OD 600 measurements 9 , 10 . In the current study, the OD 600 values of 10 times diluted samples were measured in time course of cultivation.…”

Microbial electrolysis cell accelerates phosphate remobilisation from iron phosphate contained in sewage sludge

“…The cultivation medium in the anode contained 5 g/l yeast extract, 8.2 g/l KH 2 PO 4 , 10 g/l NaHCO 3 , 20 g/l glucose and 0.2 mM Methylene Blue 24 . The microbial growth and readiness to provide power was monitored by an integrated MFC-sensor 25 . The process was started when the electromotive force of this sensor reached 0.7-0.9 V. The anodic cultivation was not protected from contamination and biofilms and…”

“…24 The microbial growth and readiness to provide power were monitored by an integrated MFC-sensor. 25 The process was started when the electromotive force of this sensor reached 0.7-0.9 V. The anodic cultivation was not protected from contamination and biolms were reused repeatedly. To verify results and trends closely, new cultivations with new anodes were employed.…”