Evaluation of the reduction in pollution of dairy products from whey fermentation in ethanol by yeast Kluyveromyces marxianus 229

Abstract

Milk whey is an important subproduct of the dairy industry, due to its generated volume and its pollution load. When launched into receiving bodies of water without prior treatment, whey may cause serious damage to the environment because it has a Chemical Oxygen Demand (COD) which lies around 60,000 mg/L. The bioconversion of the lactose from milk whey into ethanol by microrganisms capable to metabolize such disaccharide, represents a promising alternative to the treatment and disposal of the whey. It is possible to obtain a significant reduction of COD as to generate a by-product of commercial importance, which is the ethanol in this case. The aim of the study was to evaluate the production of ethanol from fermentation of cheese whey by yeast K. marxianus 229 in order to minimize its impact on the environment and produce a high commercial value by-product. The yeast Kluyveromyces marxianus 229 was used in the present study for the fermentation of milk whey, obtained after the production of the cheese type minas frescal. After 12 hours of fermentation of the whey, it was obtained a maximum ethanol production of 18.70 g/L, and an ethanolic theoretical yield of 64.10%. In relation to the reduction of organic matter (COD) content, it was decreased in 76.50%, with 48 hours of fermentation. These results showed that whey fermentation by yeast of the genus Kluyveromyces spp is an effective alternative to reduce their content of organic matter. In addition, it generates a product of high commercial interest.