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2'-Fucosyllactose (2-FL) is one of the key oligosaccharides in human milk. In the present study, the salvage guanosine 5'-diphosphate (GDP)-l-fucose biosynthetic pathway from fucose was employed in engineered Escherichia coli BL21star(DE3) for efficient production of 2-FL. Introduction of the fkp gene coding for fucokinase/GDP-l-fucose pyrophosphorylase (Fkp) from Bacteroides fragilis and the fucT2 gene encoding α-1,2-fucosyltransferase from Helicobacter pylori allows the engineered E. coli to produce 2-FL from fucose, lactose and glycerol. To enhance the lactose flux to 2-FL production, the attenuated, and deleted mutants of β-galactosidase were employed. Moreover, the 2-FL yield and productivity were further improved by deletion of the fucI-fucK gene cluster coding for fucose isomerase (FucI) and fuculose kinase (FucK). Finally, fed-batch fermentation of engineered E. coli BL21star(DE3) deleting lacZ and fucI-fucK, and expressing fkp and fucT2 resulted in 23.1 g/L of extracellular concentration of 2-FL and 0.39 g/L/h productivity. Biotechnol. Bioeng. 2016;113: 2443-2452. © 2016 Wiley Periodicals, Inc.

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2′-Fucosyllactose (2-FL), one of the most abundant oligosaccharides in human milk, has been spotlighted for its neutraceutical and pharmaceutical potentials. Microbial production of 2-FL is promising since it is efficient as compared to other production methods. In 2-FL microbial production via the salvage pathway for biosynthesis of guanosine 5′-diphosphate (GDP)-L-fucose from fucose, the conversion yield from fucose is important because of the high price of fucose. In this study, deletion of the genes (araA and rhaA) coding for arabinose isomerase (AraA) and rhamnose isomerase (RhaA) was attempted in engineered Escherichia coli for improving 2-FL production by using fucose, lactose, and glycerol. The engineered E. coli constructed previously is able to express fucokinase/GDP-L-fucose pyrophosphorylase (Fkp) from Bacteroides fragilis and the α-1,2-fucosyltransferase (FucT2) from Helicobacter pylori and deficient in β-galactosidase (LacZ), fucose isomerase (FucI), and fuculose kinase (FucK). The additional double-deletion of the araA and rhaA genes in the engineered E. coli enhanced the product yield of 2-FL to 0.52 mole 2-FL/mole fucose, and hence the concentration of 2-FL reached to 47.0 g/L, which are 44% and two-fold higher than those (23.1 g/L and 0.36 mole 2-FL/mole fucose) of the control strain in fed-batch fermentation. Elimination of sugar isomerases exhibiting promiscuous activities with fucose might be critical in the microbial production of 2-FL through the salvage pathway of GDP-L-fucose.

Meat and meat products are excellent sources of nutrients for humans; however, they also provide a favorable environment for microbial growth. To prevent the microbiological contamination of livestock foods, synthetic preservatives, including nitrites, nitrates, and sorbates, have been widely used in the food industry due to their low cost and strong antibacterial activity. Use of synthetic chemical preservatives is recently being considered by customers due to concerns related to negative health issues. Therefore, the demand for natural substances as food preservatives has increased with the use of plant-derived and animal-derived products, and microbial metabolites. These natural preservatives inhibit the growth of spoilage microorganisms or food-borne pathogens by increasing the permeability of microbial cell membranes, interruption of protein synthesis, and cell metabolism. Natural preservatives can extend the shelf-life and inhibit the growth of microorganisms. However, they can also influence food sensory properties, including the flavor, taste, color, texture, and acceptability of food. To increase the applicability of natural preservatives, a number of strategies, including combinations of different preservatives or food preservation methods, such as active packaging systems and encapsulation, have been explored. This review summarizes the current applications of natural preservatives for meat and meat products.