(414d) Charge-Tunable Polyampholytes for the Enhanced Flocculation of Cellular Biomass

The efficient concentration and separation of microorganisms from dilute culture suspensions is crucial to the success and productivity of biotechnological processes.  Previously we have developed a novel approach for the dewatering and harvesting of microalgae using polyampholyte flocculants that can be recovered and recycled in response to their pH-dependent properties, thereby addressing issues of cost and contamination in downstream processing associated with conventional flocculants.  Here we characterize these polyamphoteric flocculants with a tunable, mixed charge for the separation of microalgae species Chlorella vulgaris (UTEX 395), Nannochloropsis gaditana (CCMP526), Chlamydomonas reinhardtii (Chlamydomonas Genetics Center CC124), a yeast species Saccharomyces cerevisiae (BY4741), and wastewater sludge.  The broad applicability of the polyamphoteric flocculants is thus demonstrated for biocolloidal suspensions important as feedstocks for renewable fuels, biopharmaceuticals, and ferments.  The model ampholytic polyacrylamide-based flocculants have overall molecular charges dependent upon the system pH and provide strong electrostatic attractions to the diverse but primarily negatively-charged cellular surfaces of biological suspensions (e.g., yeast and microalgae).  The polyamphoteric flocculants provide enhanced flocculation efficiencies, up to 85% greater than comparable cationic homopolymer flocculants, with their ability to 1) adsorb to the diverse range of charge character in cellular suspensions and 2) operate in cultures over an extended range of pH.