SOLID-STATE FERMENTATION - ACID PROTEASE PRODUCTION IN CONTROLLED CO2AND O2 ENVIRONMENTS

The effect of the partial pressure of O2 and CO2 on the acid protease production in solid state fermentation by Aspergillus niger on wheat b ran was studied. A fermentation system was used, which allowed on-line reactor measurements and continuous data acquisition of pH, temperatu re, gas flow, pressure drop and CO2 production. Six paired combination s of CO2 and O2 concentrations were studied. The results showed a dire ct relationship between pressure drop, production of CO2 and temperatu re increase. The pH evolution patterns were similar in all cases but d ifferent if the measurements were made on-line or on a liquid homogena te of the fermented substrate. Acid protease production was increased when the gas had 4% CO2, (vol/vol), and it reached its highest level, a 43% increase over air, with a mixture of 4% CO2 and 21% O2. The prot ease production was strongly related to the mold metabolic activity as represented by the total CO2 evolved.