Whey utilization in a two-stage fermentation process

Abstract Whey is a major by-product of the cheese and dairy industry and has valuable nutritional constituents, however poses a major environmental risk if disposed of without prior treatment. The main components of whey except of water are lactose, lactic acid, soluble proteins, lipids, vitamins and mineral salts which give a very high biochemical oxygen demand (BOD) and chemical oxygen demand (COD) load (30,000 - 50,000 ppm and 60.000 - 80,000 ppm, respectively) to the whey. This composition provides adequate nitrogen and carbon source to be utilized by microorganisms. The aim of this study was to examine the whey utilization in a two-stage fermentation process using Lactobacillus species and Propionibacterium acidipropionici. In the first stage Lactobacillus species utilise the main part of the nitrogen source while covert lactose content to lactic acid. In the second stage Propionibacterium acidipropionici utilize lactic acid and produce propionic acid. This two-stage fermentation process can be a feasible option, both for bioremediation of whey and production of propionic acid from waste sources. High lactose conversion (>90%) to lactic acid was achieved at the first stage, but its conversion to propionic acid during the second stage was insufficient (~30%). The COD was successfully decreased during the fermentations.