Flocculation of yeast suspension by a cationic polymer: Characterization of flocculent-cell interaction

Subrata Mondal, Ranil Wickramasinghe, Leng Liow Jong, Y. K. Leong

Research output: Chapter in Book/Conference paperConference paperpeer-review


Addition of a cationic polymer can lead to the flocculation of yeast cells thus forming macroscopic floes [1]. Flocculation occurs by two main mechanisms (a) formation of macromolecular bridges between the particles, and (b) surface potential and charge reduction due to the adsorption of highly charged poly electrolytes on oppositely charged particles. The efficiency of flocculation is determined by the structure of polymer layers formed on the surface, i.e., the spacial distribution of adsorbed segments near the interface, the adsorption layer thickness, number and length of loops and tails protruding from the surface into the solution per unit area [2], In studying the flocculation behavior of microbial cells, many interaction forces need to be considered, such as, gravitational force, van der Waals attractive force, electrostatic repulsive force and specific shortrange force [3], In this study, we have investigated the flocculation of yeast cell suspensions by a cationic polymeric flocculent. The flocculation behavior of yeast cell suspensions at different times during the flocculation process is explained in terms of floe size, physicochemical surface characteristics of yeast and cell surface electric potentials (zeta potentials), dynamic mobility and Kappa value measurements. The flocculent particle size was visualized by a video camera, SILICON VIDEO® 2112 CCD. The initial rate of flocculation and growth of floe particles were dependant on the flocculent dosage. Particle size increased with increasing flocculent dosage up to certain point and then decreased. The magnitude of negative value of the zeta potential decreased and finally reached a positive plateau with increasing flocculent dose. However, during the flocculation process zeta potential was negative and magnitude decreased with the increasing flocculent dose. Our results indicate that homoflocculation occurs at the beginning of flocculation process. However, aggregation occurs at higher flocculent doses as the flocculation proceeds.

Original languageEnglish
Title of host publication2007 AIChE Annual Meeting
Publication statusPublished - 1 Dec 2007
Event2007 AIChE Annual Meeting - Salt Lake City, UT, United States
Duration: 4 Nov 20079 Nov 2007

Publication series

NameAIChE Annual Meeting, Conference Proceedings


Conference2007 AIChE Annual Meeting
Country/TerritoryUnited States
CitySalt Lake City, UT
OtherThe AIChE Annual Meeting is the premier educational forum for chemical engineers interested in innovation and professional growth. Browse proceedings below.
Internet address


Dive into the research topics of 'Flocculation of yeast suspension by a cationic polymer: Characterization of flocculent-cell interaction'. Together they form a unique fingerprint.

Cite this