The potential of lemon juice-ogi steep liquor mixtures in the reduction of Listeria monocytogenes contamination of ready-to-eat vegetables

Green synthesis of crystalline bismuth nanoparticles using lemon juice

Lemon juice effectively served as a reducing and capping agent for an easy, cost-effective, and green synthesis of crystalline bismuth nanoparticles (BiNPs) in basic aqueous media. Spherical BiNPs with a rhombohedral crystalline structure are capped by phytochemicals and stably dispersible in aqueous media. The BiNPs effectively catalyze the reduction of 4-nitrophenol to 4-aminophenol by NaBH₄.

Lemon juice effectively served as a reducing and capping agent for an easy, cost-effective, and green synthesis of crystalline bismuth nanoparticles (BiNPs) in basic aqueous media.

Antibacterial activity of the noni fruit extract against Listeria monocytogenes and its applicability as a natural sanitizer for the washing of fresh-cut produce

This study was conducted to investigate the antibacterial activity of the noni fruit extract (NFE) against Listeria monocytogenes (ATCC, 19111 and 19115) and assess its applicability for the washing of fresh-cut produce. Based on the results of the disc diffusion test, L. monocytogenes (ATCC, 19111 and 19115) was susceptible to the activity of NFE than other pathogens studied. Additionally, results of the time-kill assay indicated that NFE at a concentration of 0.5-0.7% effectively killed L. monocytogenes within 7 h. Furthermore, analysis of the intracellular components such as nucleic acids and proteins released from the bacterial cells and their SEM imaging revealed that NFE could increase the membrane permeability of cells resulting in their death. Compared to their unwashed samples, washing of romaine lettuce, spinach, and kale with 0.5% NFE gave a reduction of 1.47, 2.28, and 3.38 log CFU/g, respectively against L. monocytogenes (ATCC, 19111 and 19115), which is significantly different to that of NaOCl. A significant correlation was observed between the antibacterial effect induced due to NFE washing with the surface roughness of the fresh-cut produce than its surface hydrophobicity. Moreover, washing with NFE was not found to affect the color of the samples. These results indicated that NFE demonstrates good antibacterial activity against L. monocytogenes and can be used as a natural sanitizer to ensure the microbiological safety of fresh-cut produce.

Properties of Poly-γ-Glutamic Acid Producing-Bacillus Species Isolated From Ogi Liquor and Lemon-Ogi Liquor

Poly-γ-glutamic acid (γPGA) is a natural and promising biopolymer synthesized by Bacillus spp. during fermentation. This study isolated Bacillus spp. from ogi steep liquor (OSL) and lemon-ogi steep liquor (LOSL) using standard methods and determined the γPGA-producing ability. The antimicrobial and angiotensin-converting enzyme (ACE) inhibitory activities of γPGA polymer were evaluated and isolates were sequenced. Four isolates (TA004, TA006, TA011, TA012) selected based on phenotypic characterization and stickiness (<15 cm) showed antibacterial activity against different pathogens with the highest activity found in TA004 (22.5 mm) and least in TA011 (16.6 mm). Furthermore, time-kill assay showed that the combined γPGA polymer was more effective and demonstrated bactericidal activity over individual γPGA which are bacteriostatic in nature. All γPGA polymer exhibited ACE properties except TA011. The highest IC50 was observed in TA006 (0.11 mg/ml) and least in TA004 (0.35 mg/ml). TA004 had the highest molecular weight (261 kDa) while TA011 had the least (194.97 kDa). In addition, all γPGA exhibited characteristic peaks at 3413-3268 cm-1 and 1722-1664 cm-1 that corresponded to amine N-H stretching intensities and C = O stretching in COOH. Bacillus isolates were identified as TA004 (B. subtilis-GenBank: MH782061), TA006 (B. amyloliquefaciens- GenBank: MH782075), TA011 (B. subtilis- GenBank: MH782088), TA012 (B. subtilis- GenBank: MH782083). OSL and LOSL have the potential for developing functional foods with a valuable effect on health.