Optimisation of protein-free waste whey supplementation used for the industrial microbiological production of lactic acid

Abstract

A by-product of cheese industry – whey, is often used as a source in a microbiological lactic acid production. However, an activity of microorganisms naturally occurring in whey causing an imbalance in downstream microbiological processes. Thus, the whey permeate was indicated as appropriate medium to LA production, because a microfiltration is a type of sterilization – named very often “cold sterilization” and provide a pure and sterilize medium. The goal of this study was to identify the optimal concentrations of peptone, egg and yeast extract needed to re-supplement whey permeate medium – using for industrial scale LA production, because whey permeate is almost pure lactose solution. The highest value of LA production (27.5 g L−1) was obtained in the medium which contained 5 g L−1 peptone, 8 g L−1 egg extract and 0.2 g L−1 yeast extract. A cost of LA production using this composition medium was 0.11 € g−1 produced LA and almost 100 % of lactose was utilized after 24 h of process (only 2 % of the initial lactose was present in the spent medium). Additionally, a possible decrease of process efficiency in case of glucose (originally presents in MRS) by lactose replacement was examined. A measurement of substrate and product concentration during cultivation showed that glucose can be successfully replaced by lactose without decreasing the efficiency of production.