RESUMO
Propionic acid (PA) is an important organic compound with extensive application in different industrial sectors and is currently produced by petrochemical processes. The production of PA by large-scale fermentation processes presents a bottleneck, particularly due to low volumetric productivity. In this context, the present work aimed to produce PA by a biochemical route from a hemicellulosic hydrolysate of sorghum bagasse using the strain Propionibacterium acidipropionici CIP 53164. Conditions were optimized to increase volumetric productivity and process efficiency. Initially, in simple batch fermentation, a final concentration of PA of 17.5 gâ L-1 was obtained. Next, fed batch operation with free cells was adopted to minimize substrate inhibition. Although a higher concentration of PA was achieved (38.0 gâ L-1 ), the response variables (YP/S = 0.409 gâ g-1 and QP = 0.198 gâ L-1 â H-1 ) were close to those of the simple batch experiment. Finally, the fermentability of the hemicellulosic hydrolysate was investigated in a sequential batch with immobilized cells. The PA concentration achieved a maximum of 35.3 gâ L-1 in the third cycle; moreover, the volumetric productivity was almost sixfold higher (1.17 gâ L-1 â H-1 ) in sequential batch than in simple batch fermentation. The results are highly promising, providing preliminary data for studies on scaling up the production of this organic acid.