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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
Natural antimicrobial agents, originating from animals, plants, and microorganisms, include promising alternatives to chemical food preservatives. Examples of these include ovotransferrin from egg-white, chitosan from crustaceans and arthropods, essential oils of spices and herbs, pediocin-like bacteriocin, and microbial fermentates of some starter cultures (Juneja, Dwivedi, & Yan, 2012). Table 19.2 lists some of the FDA-approved natural antimicrobial agents. Bacteria are the most productive sources for antimicrobials. Additionally, most bacteria (>99%) are not readily cultured in laboratory media (Daniel, 2005); bacteria can enter the viable-but-nonculturable (VBNC) state under adverse conditions, such as low temperature, limited nutrient, and other stresses during food processing and storage (Giraffa & Neviani, 2001). The VBNC populations are mostly an untapped resource that may present great opportunities for researchers seeking novel antimicrobial agents. Bacteriocins of lactic acid bacteria, particularly, have been investigated extensively as potential alternatives to chemical preservatives.
Biosensors: a Potential Tool for Detection of Microbial Contaminants for Food Safety
Published in Megh R Goyal, Sustainable Biological Systems for Agriculture, 2018
Anurag Jyoti, Rajesh Singh Tomar
Methods for the detection of foodborne pathogens have been developed. Conventional culture-based methods detect pathogens based on their cultivability and often identify them based on their physical appearance. Culturing of pathogens on specific media often take 2-3 days for significant changes for identification. The culturing method is time taking and labor intensive. Therefore, its practical applications are often limited. Moreover, certain pathogens undergo in viable but non-culturable (VBNC) state, which cannot be detected by culture-based methods. In the further development of detection system, the antigen-antibody interactions have been explored for disease diagnosis. The surface antigens of pathogens are matched with available antibodies in the laboratory condition. Based on their interactions, the pathogen is confirmed.
Formation mechanisms of viable but nonculturable bacteria through induction by light-based disinfection and their antibiotic resistance gene transfer risk: A review
Published in Critical Reviews in Environmental Science and Technology, 2021
Yiwei Cai, Jianying Liu, Guiying Li, Po Keung Wong, Taicheng An
The disinfection process of water and food is designed to reduce the risk of infection by pathogenic microorganisms. The light-based disinfection process has undergone tremendous development and innovation, but the evidence provided in this review shows that it still induces bacteria to enter the VBNC state. This makes it impossible for this technology to inactivate all bacteria in the target water systems. This review first focused on changes in the morphological, physiological and virulence characteristics of bacteria entering the VBNC state, demonstrating that the cell wall, cell membrane and cytoplasm exhibit the morphological main changes. After entering the VBNC state, the bacteria undergo protein aggregation; the mass transfer efficiency and metabolic activity are reduced; the amount of ATP and cAMP is increased; and the virulence is reduced, but not necessarily completely lost. The emerging and basic detection methods of VBNC bacteria mainly, such as cell membrane integrity-mediated LIVE/DEAD Baclight assay, qPCR-mediated assays, and phage-based detection methods, were reviewed detailed. Due to the risk of resuscitation and sustained virulence, VBNC bacteria still pose a threat to human health. However, due to the existence of a large number of VBNC bacteria in the environment and their potential value in bioremediation or other domains, their environmental applicability was also considered. Finally, much attention was paid to induction conditions (especially the induction of bacteria in the VBNC state by light-based disinfection) and the formation mechanisms of VBNC bacteria. The information therein shows that physical, chemical and biological conditions, such as low temperature, antibiotics, and co-cultivation with other bacteria, may induce the VBNC state. In addition, various light-based disinfection technologies that induce the formation of VBNC bacteria were reviewed. The formation mechanisms of VBNC bacteria mainly involve the stringent response, the general stress response system and the TA system. All three regulatory systems can induce the formation of VBNC bacteria, but the general stress response system and TA system are regulated by stringent response. In addition, much attention was paid to HGT of ARGs during and after the formation of VBNC bacteria induced by light-based disinfection. After entering the VBNC state, conjugation of the donor bacteria may be inhibited, while the recipient bacteria can still carry out conjugative transfer, suggesting that light-based disinfection may be able to induce bacteria to enter the VBNC state while simultaneously accelerating the conjugation of ARGs.