Fermentation of lactose to ethanol in cheese whey permeate and concentrated permeate by engineered Escherichia coli

Abstract

BackgroundWhey permeate is a lactose-rich effluent remaining after protein extraction from milk-resulting cheese whey, an abundant dairy waste. The lactose to ethanol fermentation can complete whey valorization chain by decreasing dairy waste polluting potential, due to its nutritional load, and producing a biofuel from renewable source at the same time. Wild type and engineered microorganisms have been proposed as fermentation biocatalysts. However, they present different drawbacks (e.g., nutritional supplements requirement, high transcriptional demand of recombinant genes, precise oxygen level, and substrate inhibition) which limit the industrial attractiveness of such conversion process. In this work, we aim to engineer a new bacterial biocatalyst, specific for dairy waste fermentation.ResultsWe metabolically engineered eight Escherichia coli strains via a new expression plasmid with the pyruvate-to-ethanol conversion genes, and we carried out the selection of the best strain among the candidates, in terms of growth in permeate, lactose consumption and ethanol formation. We finally showed that the selected engineered microbe (W strain) is able to efficiently ferment permeate and concentrated permeate, without nutritional supplements, in pH-controlled bioreactor. In the conditions tested in this work, the selected biocatalyst could complete the fermentation of permeate and concentrated permeate in about 50 and 85 h on average, producing up to 17 and 40 g/l of ethanol, respectively.ConclusionsTo our knowledge, this is the first report showing efficient ethanol production from the lactose contained in whey permeate with engineered E. coli. The selected strain is amenable to further metabolic optimization and represents an advance towards efficient biofuel production from industrial waste stream.Electronic supplementary materialThe online version of this article (doi:10.1186/s12896-017-0369-y) contains supplementary material, which is available to authorized users.

Ethanol Production from Cheese Whey and Expired Milk by the Brown Rot Fungus Neolentinus lepideus

“…However, a strain of the homo-lactic fermentative bacterium, Lactococcus lactis, has been genetically engineered to be able to efficiently produce ethanol from whey [11]. Similarly, Escherichia coli can assimilate lactose, but not ferment it, and some recombinant E. coli capable of fermenting whey have been constructed [12][13][14].…”

The Potential Production of the Bioactive Compound Pinene Using Whey Permeate

“…Whey permeate is currently used as a fermentation medium for the production of single cell protein, lactic acid, vitamin B12 and ethanol. More specifically, recombinant E. coli strains have produced ethanol using untreated whey permeate as a fermentation medium (Table 1) [51]. This indicates that whey permeate may be a suitable medium for other recombinant E. coli strains or other recombinant microorganisms.…”

“…In fact, multiple studies have demonstrated the ability of E. coli to metabolize the lactose within whey permeate [6,8,16,26,52]. It was reported in 2017 that an E. coli strain efficiently grew and fermented untreated whey permeate without nutritional supplementation in a pH-controlled bioreactor [51]. Recent efforts also indicate that recombinant homofermentative E. coli strains expressing the Vitreoscilla hemoglobin successfully produce ethanol using rehydrated whey powder and autoclaved cheese whey as a medium [53,54].…”

Cell-free prototyping strategies for enhancing the sustainable production of polyhydroxyalkanoates bioplastics

“…Whey permeate is a waste by-product of industrial cheese production that has been proposed as an attractive low-cost feedstock for microbial PHAs production in vivoparticularly P(3HB) (Bosco and Chiampo, 2010;Ryan and Walsh, 2016). Whey permeate contains a high percentage of lactose (>70% of the mass), which can be readily metabolised in vivo by E. coli MG1655, using its β-galactosidase enzyme, to generate glucose for glycolytic processing into Acetyl-CoA (Pasotti et al, 2017).…”