A new model for the reconstruction of biomass history from carbon dioxide emission during batch cultivation of Geotrichum candidum.

A non-structured model has been developed to describe the CO2 emission during growth of Geotrichum candidum on a lactate + peptone-based liquid medium. From the nitrogen and carbon mass balances, it was shown that about 50% of the total CO2 released was from the metabolism of the energy supply for biosynthesis, and the remaining from that for maintenance; thus, CO2 production was considered to be partially associated with growth. The model fitted the experimental data as long as a net growth was observed (0-50 h). The coefficients for growth- and non-growth-associated CO2 production were A = 0.646 (dimensionless) and B = 0.017 h(-1), respectively. From the coefficients of the model and the CO2 history data, the biomass kinetics has been reconstructed, and the calculated biomass concentrations agree fairly well with the experimental data. From this, measurement of the CO2 evolved may be used as an indirect and non-intrusive method of monitoring fungal growth during the first 50 h of cultivation.