Fermentation kinetics and process development in the production of deicers (calcium magnesium acetate and calcium magnesium propionate) from lactose of whey

More than 30 million tons of rock salt are used currently in the US annually for highway deicing to maintain safe driving conditions in winter. This has resulted in corrosion related damage to the highway infrastructures and environmental damage from contamination of surface and ground water supplies. This research is aimed at developing an environmentally safe substitute for rock salt from inexpensive raw materials. Previous studies have shown that calcium magnesium acetate (CMA) and calcium magnesium propionate (CMP) are suitable substitutes for rock salt. A two-stage fermentation system using two inexpensive raw materials, whey permeate and lime, was studied for the production of CMA and CMP. Batch, fed-batch, and continuous fermentation experiments were conducted with whey permeate, raw whey, and synthetic lactose medium and using lime and NaOH for pH control. Modeling of the process and kinetics were conducted to estimate parameters and optimal operating conditions. The results show that two-stage facultative anaerobic fermentation with lime for pH control is a very promising method for CMA and CMP production. In the first stage, lactose is converted to lactic acid using Lactobacillus plantarum , and in the second stage, lactic acid is converted to propionic and acetic acids using Propionibacterium acidipropionici P200910. The two-stage system gave a product yield of about 80% to 90% by avoiding the loss of CO₂ during fermentation. In comparison, the yield with a single stage process is only 50% to 60%. The mode of fermentation operation in the second stage significantly affects the fermentation process performance. Simulation results based on continuous fermentation process models show that the optimal dilution rate for first stage is around 0.06–0.08 1/hr, and 0.03–0.04 1/hr for the second stage. Economic analysis based on the laboratory data and equipment and raw material prices from fourth quarter of 1997 indicate an estimated CMA/CMP product cost of {dollar}332/ton for a 40 ton/day plant. This process has great potential for implementation since the current price of CMA is about {dollar}1000/ton.