Shear rate and microturbulence effects on the synthesis of proteases by Jacaratia mexicana cells cultured in a bubble column, airlift, and stirred tank bioreactors

Abstract

Cysteine proteases from Jacaratia mexicana, an endemic Mexican plant, could compete in industrial applications with papain. Currently the only way to obtain these proteases is by extracting them from the wild plant. An alternative source of these enzymes is by J. mexicana suspension culture. In this work, this culture was carried out in airlift, bubble column and stirred tank bioreactors, and the effects of shear rate and microturbulence on cell growth, protein accumulation and proteolytic activity were determined. The shear rates in the stirred tank, bubble column and airlift bioreactors were 274 1/s, 13 1/s and 36 1/s respectively, and microturbulences (symbolized by λ, in units of μm) were 46, 79, and 77 μm, respectively. Protein levels and proteolytic activity were linearly correlated with both shear rate and microturbulence. A higher shear rate and a more intensive microturbulence occurred in the stirred tank, producing higher protein accumulation and higher proteolytic activity compared with those of the other two bioreactor systems. Higher shear rate and microturbulence had an elicitor effect on protease synthesis, because microturbulence in stirred tank bioreactors was lower than the average length of J. mexicana cells. Furthermore, cells in the stirred tank were smaller and thinner than those grown in shake flask, bubble column and airlift bioreactors. In summary, proteases were produced by J. mexicana cell cultures in a stirred tank under conditions of high shear rate and intensive microturbulence, which are similar to those which occur in industrial stirred tanks. These results encourage continuation of the process development for large scale production of these proteases by this technology.