Harvesting and dewatering yeast by microflotation

Microbubble has been applied for the recovery of yeast cells from their growth medium using the bioflocculant-chitosan. Results reaching 99% cell recovery were obtained under various conditions examined. The result of bubble size distribution showed that mean bubble size increased as microbubble diffuser pore size was increased. Also, cell recovery efficiency was a function of both bubble size and particle size (cell size). For smaller particles (<50 mu m), relatively smaller bubbles (<80 mu m) were found to be more effective for recovery, otherwise, relatively larger bubbles (80-150 mu m) proved to be efficient in recovering larger particles (particle size: similar to 250 mu m). Acidic and neutral pHs were effective in separation as hydrophobic particles were formed. As pH tends toward alkalinity, flocs become more hydrophilic, leading to low recovery from the aqueous solution. In addition, separation efficiency was dependent on flocculant dose as increase in concentration improved flocculation and consequently, yeast recovery. However, above a critical concentration, overdosing occurred and inadvertently, recovery efficiency decreased. The application of chitosan as a bioflocculant and the subsequent application of microflotation for the separation of yeast cells proved effective and promises several advantages over non-bubble based separation techniques that preclude continuous industrial-scale production. (C) 2013 Published by Elsevier B.V.