Chemical and Enzymatic Protein Cross-Linking To Improve Flocculant Properties

Some proteins promote the flocculation of aqueous suspensions, but proteins are much smaller than modern polymeric flocculants, and they are often not as potent. In this study, two globular proteins, hemoglobin (Hb) and bovine serum albumin (BSA), were cross-linked through either chemical or enzymatic means. The degree of cross-linking was approximately 95%. Compared to the native proteins, the cross-linked proteins had a 20–30 fold increase in molecular weight and a reduced isoelectric point. Cross-linked proteins appear to have lost the secondary structures present in their native counterparts and do not go through organized structural transitions upon heating. The cross-linked Hb sample showed a higher peak clarification efficiency (KCE = 2.96) compared to its BSA counterpart, indicating its potential to be used as a flocculant for water clarification. Interestingly, native BSA has no flocculant activity (KCE = 0, 0% clarification), but enzymatically cross-linked BSA has substantial activity (peak KCE ...