In microbial fermentation processes, particularly those involving Corynebacterium species for

secondary metabolite production, scale-up from laboratory to pilot volumes (300–500 L) often reveals

discrepancies that undermine commercial viability. In this instance, upstream fermentation consistently

achieved titers of 18–22 g/L, aligning with performance targets derived from smaller-scale (5–10 L)

experiments. However, downstream recovery faltered due to abrupt rheological changes in the broth

after approximately 72 hours of fermentation. Apparent viscosity surged 3–4-fold compared to lab

benchmarks, correlating with total suspended solids surpassing 18% w/v. This non-Newtonian, shearthinning

behavior—where viscosity decreases under shear stress but rebounds at rest—invalidated

equipment sizing assumptions, leading to operational failures.