Effect of the variation of the level of lactose conversion in an immobilized lactase reactor upon operating costs for the production of baker’s yeast from hydrolyzed cottage cheese whey permeate

Abstract

Operating costs for the production of Baker’s yeast from hydrolyzed permeate from the ultrafiltration of cottage cheese whey were calculated as a function of the level of lactose conversion in the immobilized lactase reactor. These costs were calculated for the case of 90% conversion of lactose in the reactor and compared to those that result when running the reactor at lower conversions with recycle of unreacted lactose. Total operating costs were estimated by combining individual operating costs for the immobilized enzyme reactor, costs associated with processing a lactose recycle stream, and energy costs associated with cooling the reactor feed stream and sterilizing the hydrolysate stream. It was determined that operating costs are minimized at about 9.9 ¢/lb. of lactose when the reactor is run at approx. 72% conversion. This represents a savings of 2.4 ¢/lb. of lactose over the case of a once-through 90% conversion of lactose in the reactor.