Two-stage fermentation process for the production of calcium magnesium acetate and propionate road deicers

Calcium magnesium acetate (CMA) and propionate (CMP) are environmentally benign deicing chemicals that can replace sodium chloride that is widely used on roads and highways at present for snow and ice control to provide safe driving conditions during winter. The price of CMA from petroleum-derived acetic acid is quite expensive. Anaerobic fermentations have not proven economical due to the low acid productivity and concentrations. A novel method for the production of CMA and CMP from lactose and whey permeate via a two-stage anoxic fermentation system, with calcium hydroxide for pH control is described in this paper. A homolactic bacterium Lactobacillus plantarum is used to convert lactose to calcium magnesium lactate (CML) in the first stage, and Propionicibacterium acidipropionici P200910 is used to convert CML to CMA and CMP in the second stage. In both stages, the conversion rates were 90% (w/w). Lactic acid productivity was 2.03 g/L/h in the first stage at a dilution ratio of 0.06 h⁻¹. Propionic and acetic acid yield was 1.79 g/L/h at a dilution rate of 0.05 h⁻¹. Calcium hydroxide addition did not significantly alter the overall yield of acids in either stage. However, the ratio of concentration of propionate to acetate in the final product changed from 3.0 when NaOH is used to 2.0 when lime is applied for pH control. After separation of the biomass, the liquid with a total concentration of 48–55 g/L of CMA and CMP can be processed to obtain a solid road deicer product.