NONFLOCCULENT VERSUS TOTAL BIOMASS RATIO AS A CRITERION FOR STARTING THE BIOMASS SEPARATION PROCESS

We introduce the ratio of nonflocculent versus total biomass as a crit erion for starting cell separation from the medium. This criterion can be applied for the automation of the process regardless of the proces s dynamics. Its minimum indicates the optimum period of time for the s tart of the separation process with regard not only to nonflocculent c ell concentration, but also medium attributes. In contrast to the conc entration of nonflocculent cells, which has two minima, first at the b eginning of the process and another broader one in the period during w hich maximum flocculation is present, the ratio has a single minimum a nd can therefore be implemented as a criterion for cell separation. To calculate the ratio value, in addition to an on-line method for nonfl occulent biomass measurement described elsewhere, an on-line method fo r the total biomass of flocculent yeast is proposed. It is based on th e absorbency measurement of the cell biomass, previously deflocculated by EDTA. Therefore, it can be applied in bioprocesses with transparen t media and yeast that can be deflocculated by EDTA. (C) 1998 John Wil ey & Sons, Inc. Biotechnol Bioeng 59: 647-650, 1998.