TECH
Why fermentation feeds are difficult
Fermentation broths contain cells, proteins, polysaccharides, salts, pigments and target metabolites, with strong batch variation. Insufficient pretreatment accelerates fouling, while excessive pretreatment may reduce yield and raise cost.
Target and impurity molecular weight, charge and concentration should guide the sequence of UF, NF and RO.
The role of nanofiltration
After clarification, NF can concentrate small products, pass inorganic salts, or retain pigments and larger impurities. Membrane cut-off and surface properties must match the product.
Concentration work emphasizes yield and retentate viscosity; desalination also balances salt passage, product retention and diafiltration water.
Stable operation depends on system control
Crossflow velocity, recovery, temperature and staged pressure drop help control concentration polarization. Normalizing data for temperature and concentration prevents feed variation from being mistaken for membrane decline.
Cleaning chemistry should match proteins, pigments, oils or scale, with recovery judged by flux, pressure drop and rejection together.