GAS CONCENTRATION AND TEMPERATURE-GRADIENTS IN A PACKED-BED SOLID-STATE FERMENTER

In solid-state fermentation (SSF), interaction of heat and mass transf er with biochemical reaction (growth associated enzyme production) aff ects the bioreactor performance. This interaction was earlier observed to cause temperature and gaseous concentration gradients which reduce d the effective bed height of the bioreactor. Since forced aeration is known to alleviate this problem, a packed column bioreactor with forc ed aeration was employed in the present study. Using wheat bran and As pergillus niger CFTRI 1105, experiments were conducted for the product ion of the enzyme amyloglucosidase at various air flow rates. Temperat ures and gas concentrations were recorded and enzyme activities estima ted at different bed heights during the course of SSF. Gas concentrati on and temperature gradients decreased with increasing air flow rate. The packed column allowed the use of larger bed heights and yielded hi gher enzyme activities (6,260 Units/gDMB) than trays (345 Units/gDMB). Enzyme activity was affected more by temperature than concentration g radients, and increased with air flow rates.