Abstract
This study aims at exploiting salinity stress as an innovative, simple, and cheap method to enhance the production of antioxidant metabolites and enzymes from bacteria for potential application as functional additives to foods and pharmaceuticals. We investigated the physiological and biochemical responses of four bacterial isolates, which exhibited high tolerance to 20% NaCl (wt/vol), out of 27 bacterial strains isolated from Aushazia Lake, Qassim region, Saudi Arabia. The phylogenetic analysis of the 16S rRNA genes of these four isolates indicated that strains ST1 and ST2 belong to genus Bacillus, whereas strains ST3 and ST4 belong to genus Planococcus. Salinity stress differentially induced oxidative damage, where strains ST3 and ST4 showed increased lipid peroxidation, lipoxygenase, and xanthine oxidase levels. Consequently, high antioxidant contents were produced to control oxidative stress, particularly in ST3 and ST4. These two Planococcus strains showed increased glutathione cycle, phenols, flavonoids, antioxidant capacity, catalase, and/or superoxide dismutase (SOD). Interestingly, the production of glutathione by Planococcus strains was some thousand folds greater than by higher plants. On the other hand, the induction of antioxidants in ST1 and ST2 was restricted to phenols, flavonoids, peroxidase, glutaredoxin, and/or SOD. The hierarchical analysis also supported strain-specific responses. This is the first report that exploited salinity stress for promoting the production of antioxidants from bacterial isolates, which can be utilized as postbiotics for promising applications in foods and pharmaceuticals.
Highlights
Oxidation of food can occur during various steps of handling and leads to the formation of bad flavors, loss of essential fatty acids, fat−soluble vitamins and other bioactive compounds, and development of possibly poisonous compounds, so turning fat−rich foods unsafe for human consumption (Scott, 1997; Min and Ahn, 2005)
We demonstrated that salinity promotes the production of antioxidant metabolites and enzymes, which can be utilized as postbiotics for potential application as functional additives to foods and pharmaceuticals to enhance food stability and to promote human health
A total of 27 bacterial isolates were retrieved from the collected samples; four strains of them exhibited a good growth capability under the highest salt concentration (20% NaCl), whereas the remaining 23 isolates could not survive at that high salt stress
Summary
Oxidation of food can occur during various steps of handling and leads to the formation of bad flavors, loss of essential fatty acids, fat−soluble vitamins and other bioactive compounds, and development of possibly poisonous compounds, so turning fat−rich foods unsafe for human consumption (Scott, 1997; Min and Ahn, 2005). Free radical–mediated oxidation of lipids is an important concern for researchers and food processors (Shahidi and Zhong, 2010). In this context, antioxidants have received considerable interest in recent years. The addition of antioxidants has become the most efficient, appropriate, and economical strategy for protecting food lipids and avoiding deterioration of food quality. In medicine, they are used as healthpromoting agents owing to their capability to enhance the effectiveness of the body’s antioxidant defense mechanisms (Shahidi and Zhong, 2010). There is a global need to replace synthetic antioxidants with natural ones
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