Interaction of transport resistances with biochemical reaction in packed-bed solid-state fermentors: effect of temperature gradients

In solid-state fermentation, the interaction of transport phenomena with biochemical reactions has a considerable effect on the productivity of the bioreactor. Previous work on solid-state fermentation in tray fermentors in our laboratory indicated that heat transfer resistance results in steep temperature gradients within the solid substrate bed, which in turn adversely affect the biochemical reaction and enzyme activity. This problem of heat accumulation during the course of fermentation has been alleviated to a considerable extent using a packed-column bioreactor with forced aeration in the present work. Experimental studies were conducted in a packed-column bioreactor utilizing wheat bran as substrate and the fungus Aspergillus niger CFTRI 1105 for the production of the enzyme amyloglucosidase. The enzyme activities were estimated and temperatures were recorded at different bed heights, for different air flow rates during the course of fermentation. The results indicated that the temperature gradients caused by heat transfer resistances were reduced considerably with corresponding increases in enzyme activity