Fermentation of lactose to bio-ethanol by yeasts as part of integrated solutions for the valorisation of cheese whey.
Cheese whey, the main dairy by-product, is increasingly recognized as a source of many bioactive valuable compounds. Nevertheless, the most abundant component in whey is lactose (ca. 5% w/v), which represents a significant environmental problem. Due to the large lactose surplus generated, its conversion to bio-ethanol has long been considered as a possible solution for whey bioremediation. In this review, fermentation of lactose to ethanol is discussed, focusing on wild lactose-fermenting yeasts, particularly Kluyveromyces marxianus, and recombinant Saccharomyces cerevisiae strains. The early efforts in the screening and characterization of the fermentation properties of wild lactose-consuming yeasts are reviewed. Furthermore, emphasis is given on the latter advances in engineering S. cerevisiae strains for efficient whey-to-ethanol bioprocesses. Examples of industrial implementation are briefly discussed, illustrating the viability of whey-to-ethanol systems. Current developments on strain engineering together with the growing market for biofuels will likely boost the industrial interest in such processes.
IBB-Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
Pedro M R
PM
Guimarães
José A
JA
Teixeira
Lucília
L
Domingues
D002611:Cheese / Q000382:microbiology*; D000431:Ethanol / Q000378:metabolism*; D005658:Fungi / Q000502:physiology*; D024861:Genetic Enhancement / Q000379:methods*; D007785:Lactose / Q000378:metabolism*
D000431:Ethanol; D007785:Lactose