Abstract
Microbiological contamination and oxidative damage are the two main challenges in maintaining quality and improving shelf-life of foods. Here, we developed a Lactococcus lactis fermentation system that could simultaneously produce nisin, an antimicrobial peptide, and γ-aminobutyric acid (GABA), an antioxidant agent. In this system, we metabolically engineered a nisin producing strain L. lactis F44 for GABA production by expression of glutamate decarboxylase and glutamate/GABA antiporter. GABA biosynthesis could facilitate nisin production through enhancing acid resistance of the strain. By applying a two-stage pH-control fermentation strategy, the engineered strain yielded up to 9.12 g/L GABA, which was 2.2 times higher than that of pH-constant fermentation. Furthermore, we demonstrated the potential application of the freeze-dried fermentation product as a preservative to improve the storage performance of meat and fruit. These results suggested that the fermentation product of nisin–GABA co-producing strain could serve as a cost-effective, easily prepared, and high-performance food preservative.
Highlights
Microbiological contamination is a crucial issue in food preservation resulting in the alteration of food qualities including nutritional value, flavor, and tastes (Chatterjee and Abraham, 2018)
Lactococcus lactis F44, exhibiting high production of nisin, was used to construct nisin and GABA co-producing strain in this research
GABA is synthesized from glutamate in a decarboxylation reaction catalyzed by glutamate decarboxylase (GAD), and pyridoxal-5 phosphate (PLP) is an essential cofactor for the biotransformation process (Xu et al, 2017)
Summary
Microbiological contamination is a crucial issue in food preservation resulting in the alteration of food qualities including nutritional value, flavor, and tastes (Chatterjee and Abraham, 2018). Some of them, such as BHA or butylated hydroxytoluene (BHT), are suspected to present toxicity effects to humans (Bauer et al, 2001; de Oliveira Pateis et al, 2018). Their potential health threats to humans have prompted investigations into applying natural preservatives in recent years (Przybylski et al, 2016). A natural antimicrobial peptide, exhibits broad-spectrum antimicrobial activity against many of the Gram-positive foodborne bacteria, such as Listeria and Clostridium (Cotter et al, 2005; Barbosa et al, 2017) It exhibits antimicrobial activity against some Gram-negative bacteria
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