Schizosaccharomyces pombe fed-batch culture in the presence of cadmium for the production of cadmium sulphide quantum semiconductor dots

A feedback-controlled fed-batch process during the uptake of cadmium sulphate for the subsequent production of cadmium sulphide quantum semiconductors using Schizosaccharomyces pombe was developed. The system is capable of maximising S. pombe biomass yield per fermentation and as a result, maximises cadmium sulphide quantum semiconductor production per fermentation. Using a S. pombe chemostat, biomass production was maximised with respect to minimising glucose repression and ethanol production when the specific growth rate was 0.1 h−1. Direct feedback control of the glucose feed in a fed-batch fermentation with RQ data at a set-point of RQ = 1 and the specific growth rate of 0.1 h−1 resulted in reduced glucose repression and ethanol production even after the cytotoxic heavy metal cadmium was added to the fermentation. A final biomass yield (dry cell weight) of 18.2 g/liter for the induction of CdS quantum semiconductors was a 4 fold increase in the biomass available compared to previous batch fermentations carried out by the authors.