Solid substrate fermentation of Monascus purpureus: Growth, carbon balance, and consistency analysis

Solid substrate fermentation (SSF) of Monascus purpureus on rice is a promi sing new technology for obtaining natural pigments. However, before attempt s can be made at maximizing pigment yield, all significant macroscopic comp ounds should be assayed. Here, Monascus purpureus has been grown on rice in batch mode, and the evolution of the main components, biomass, residual ri ce, O-2, CO2, ethanol, acetic acid, and pigments, have been followed. This set of data, never previously studied for Monascus SSF, allowed both the pe rformance of a macroscopic elemental balance, which accounted for 83-94% of the initial substrate carbon, and a check of data consistency. Standard co nsistency analysis showed a significant underestimation of the nitrogen fra ction of biomass, but it was unable to discriminate the errors in the carbo n balance as a result of the simultaneous presence of two gross errors in t he system. A simple stoichiometric model in tandem with consistency analysi s explained unaccounted carbon as an underestimation of CO2 and ethanol. Us ing the simplified method to estimate ethanol, the macroscopic balance acco unted for 87-99% of the initial carbon.