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Role of Microbes in Environmental Sustainability and Food Preservation
Published in Ram Chandra, R.C. Sobti, Microbes for Sustainable Development and Bioremediation, 2019
Huang En, Ravi Kr. Gupta, Fangfei Lou, Sun Hee Moon
The term lantibiotics is the abbreviation of lanthionine-containing antibiotics. These are ribosomally synthesized peptides that contain lanthionines, which are formed during posttranslational modification. The characteristic residues in lantibiotics included dehydroalanine (Dha), dehydrobutyrine (Dhb), lanthionine (Lan), and methyllanthionine (MeLan). Dha and Dhb residues are unsaturated dehydroamino acids derived from serine and threonine, respectively. Dha or Dhb residue can form a thioether bond with the cysteine residue in the prepropeptide during biosynthesis, resulting in the unusual residues, lanthionine or methyllanthionine, respectively (Willey & Van der Donk, 2007). The chemical structure of paenibacillin (He et al., 2008) and the unusual residues are shown in Figure 19.1.
Production of nisin from Lactococcus lactis in acid-whey with nutrient supplementation
Published in Preparative Biochemistry & Biotechnology, 2023
Sahana Vijayakumar, Vishnu G., Prajna Rao Krishnapura, Regupathi Iyyaswami
A bacteriocin, Nisin, produced by lactic acid bacteria (LAB) has garnered a lot of attention as a natural preservative in the food industry because of its proven safety and potency against various food spoilage microbes and pathogenic bacteria.[7] Nisin is a small amphiphilic peptide of about 3000 Da produced by the Lactococcus lactis species with antagonistic activity against many gram-positive bacteria.[8] Nisin belongs to the ‘Type A’ lantibiotics, whose primary mode of inactivation is forming pores in the cytoplasmic membrane of the microorganisms. The presence of unusual amino acids in nisin, such as lanthionines, provides thermostability, acid tolerance, resistance to proteolytic degradation, and antibiotic activity. Therefore, nisin can be used as a preservative even with foods processed at higher temperatures or food systems with natural proteases.[7] Nisin is effective in small concentrations. It is also toxicologically safe and not known to cause any side effects or adverse interactions like antibiotics.[9] Hence, it is considered “Generally Regarded as Safe (GRAS)” by US Food and Drug Administration,[10] and listed as an approved food additive in the EU.[11] The most prominent antimicrobial peptide, nisin, is currently used as a food preservative in dairy, beverage, meat, and vegetable products.[12]
Characterization and mode of action of a potent bio-preservative from food-grade Bacillus licheniformis MCC 2016
Published in Preparative Biochemistry and Biotechnology, 2019
Nithya Vadakedath, Prakash M. Halami
Genetically engineered reporter strains of B. subtilis have been used for the rapid detection of the MOA of antibacterial compounds.[26,27,38] De Pascale et al.[38] used B. subtilis strain expressing the Enterococcus faecium vanRS and vanH–lacZ fusion genes as a reporter strain for the MOA study. In the presence of cell wall inhibitors and lysozyme, it is induced to produce β-galactosidase activity. They claimed that reporter-strain-based antibiotic discovery is a powerful tool exhibiting operational ease and specificity. In this study as well, the β-galactosidase activity of the reporter strains (BSF 2470, TMB 488, TMB 299, and TMB 279) treated with different concentrations of ppABP (0, 0.4, 2.0, 4.0, or 8.0 mg mL−1) was assayed to determine the MOA of the ppABP of MCC 2016. The reporter strains B. subtilis BSF 2470 and TMB 488 have a promoter, which is induced by cell wall acting lipid II binding antibacterial substances.[26,39] Chemical substances, such as SDS and ethanol, etc. also generally induce BSF 2470, whereas, the induction of β-galactosidase activity of TMB 488 is very specific and particularly differentiate cell wall acting antibacterial substances. While the reporter strains TMB 299 and TMB 279 are induced by lipid II binding lantibiotics (viz. nisin, subtilin, actagardine, and gallidermin) and lipid II lantibiotic bacitracin,[40] respectively. The ppABP of MCC 2016 was found to induce the reporter strains, BSF 2470, TMB 488, and TMB 299 (Fig. 6). No induction was noticed for the strain TMB 279 (Fig. 6). Maximum induction of β-gal for BSF 2470 and TMB 299 was observed at 2 mg mL−1 ppABP. In the case of TMB 488, maximum induction was noted at 8 mg mL−1 (27 Miller units) (Fig. 6). The induction of BSF 2470, TMB 488, and TMB 299 strains but not TMB 279 by the ABP of MCC 2016 indicates that it is a cell wall acting cationic l antibiotic similar to nisin or subtilin and is not bacitracin.