Unique characteristics of self-assembly of bovine serum albumin and fucoidan, an anionic sulfated polysaccharide, under various aqueous environments

Interpolymeric complexes of bovine serum albumin (BSA)/fucoidan (weight ratio of 5:1) were prepared by decreasing pH in the absence and presence of NaCl. The turbidity drastically increased at pH 4.5 (pHφ1) and the maximum biopolymer interactions induced at pH 4.0 (pHopt). The viscosity of BSA/fucoidan complexes at pH 4.0 was 1.5 times higher than that of individual protein solutions. These results reflected that both BSA and sulfated dominant fucoidans (NH3+ and –SO3−) favored the formation of BSA/fucoidan complexes with very dense and compact internal structures. On the other hand, increasing NaCl concentration (from 0 to 1 M) shifted the critical pH (pHφ1) to a more acidic value, which may be explained by salt screening. Interestingly, 0.01 M of NaCl dissociated the aggregated BSA/fucoidan complexes into a soluble state at pH = 4.5.