The search for bacteria-labeling agents that are more efficient and less toxic compared to existing staining dyes is ongoing. Fluorescent quantum dots and carbon dots (CDs) have been extensively researched for various bioimaging applications. Priority is given to CDs due to several advantages, including lower toxicity, versatility in tuning their properties, and better photostability compared to metal-based quantum dots. Although significant progress is still needed to replace existing dyes with CDs for bacteria labeling, they offer promising potential for further improvement in efficiency. Surface charges and functional groups have been reported as decisive factors for bacterial discrimination and live/dead assays; however, a complete guideline for preparing CDs with optimum properties for efficient staining and predicting their labeling performance is lacking. In this review, we discuss the application of fluorescent CDs for bacterial labeling and the underlying mechanisms and principles. We primarily focus on the application and mechanism of CDs for Gram differentiation, live imaging, live/dead bacteria differentiation, bacterial viability testing, biofilm imaging, and the challenges associated with application of CDs. Based on proposed mechanisms of bacterial labeling and ambiguous results reported, we provide our view and guidelines for the researchers in this field to overcome the challenges associated with bacteria labeling using fluorescent CDs.

Probiotics have recently received significant attention due to their various benefits, such as the modulation of gut flora, reduction of blood sugar and insulin resistance, prevention and treatment of digestive disorders, and strengthening of the immune system. One of the major issues concerning probiotics is the maintenance of their viability in the presence of digestive conditions and extended shelf life during storage. To address this concern, numerous techniques have been explored to achieve success. Among these methods, the microencapsulation of probiotics has been proposed as the most effective way to overcome this challenge. The combination of nanomaterials with biopolymer coating is considered a novel approach to improve its viability and effective delivery. The use of polysaccharides and proteins-based bionanocomposites for microencapsulation of probiotics has emerged as an efficient and promising approach for maintaining cell viability and targeted delivery. This review article aims to investigate the use of different bionanocomposites in microencapsulation of probiotics and their effect on cell survival in long-term storage and harsh conditions in the gastrointestinal tract.

BACKGROUND: Bacteria are known to live inside architectural structures called biofilms. Though standard biofilms have been studied extensively for more than 50 years, little is known about dry-surface biofilms (DSBs). Since 2012, DSBs have been described in several scientific papers, but basic knowledge about the viability and culturability of bacteria remains limited.
OBJECTIVE: To conduct a systematic review to determine whether bacteria inside DSBs are viable, culturable, and enumerable.
METHODS: Eligible articles had to deal with DSBs containing at least one bacterial species involved in healthcare-associated infections, which developed in actual healthcare environments (in-situ) or with the help of any biofilm model (in-vitro).
RESULTS: Twenty-four articles were included in the review. Whereas most of them isolated viable bacteria (87% in situ; 100% in vitro), no in-situ study quantified culturable bacteria in the biofilm per unit area. Conversely, 100% of in-vitro studies cultured the bacteria from controls and 94.4% supplied an enumeration of them. Culturable bacteria also grew after 78% of the cleaning, disinfection, or sterilization protocols tested. Microscopic observations after staining the samples with live/dead fluorescent probes (Baclight®) showed large amounts of viable cells in culture-negative samples.
CONCLUSIONS: Our study questions the efficacy of current methods for microbiological monitoring of surfaces, since these methods are only based on bacterial culturability. To improve both surface monitoring and cleaning and disinfection protocols, it is necessary to integrate the concept of DSBs which appears to contain a significant amount of viable but non-culturable bacteria.

Ultrasound (US) technology is recognized as one of the emerging technologies that arise from the current trends for improving nutritional and organoleptic properties while providing food safety. However, when applying the US alone, higher power and longer treatment times than conventional thermal treatments are needed to achieve a comparable level of microbial inactivation. This results in risks, damaging food products\' composition, structure, or sensory properties, and can lead to higher processing costs. Therefore, the US has often been investigated in combination with other approaches, like heating at mild temperatures and/or treatments at elevated pressure, use of antimicrobial substances, or other emerging technologies (e.g., high-pressure processing, pulsed electric fields, nonthermal plasma, or microwaves). A combination of US with different approaches has been reported to be less energy and time consuming. This manuscript aims to provide a broad review of the microbial inactivation efficacy of US technology in different food matrices and model systems. In particular, emphasis is given to the US in combination with the two most industrially viable physical processes, that is, heating at mild temperatures and/or treatments at elevated pressure, resulting in techniques known as thermosonication, manosonication, and manothermosonication. The available literature is reviewed, and critically discussed, and potential research gaps are identified. Additionally, discussions on the US\'s inactivation mechanisms and lethal effects are included. Finally, mathematical modeling approaches of microbial inactivation kinetics due to US-based processing technologies are also outlined. Overall, this review focuses only on the uses of the US and its combinations with other processes relevant to microbial food decontamination.

Microorganism encapsulation protects them from stressful conditions and assists in maintaining their viability, being especially beneficial when the carrier material is a renewable and biodegradable biopolymer, such as starch. Here, a systematic mapping was performed to provide a current overview on the use of starch-based systems for microbial encapsulation. Following well-established guidelines, a systematic mapping was conducted and the following could be drawn: 1) there was a significant increase in publications on microbial encapsulation using starch over the past decade, showing interest from the scientific community, 2) ionotropic gelation, emulsification and spray drying are the most commonly used techniques for starch-based microbial encapsulation, and 3) starch play important functions in the encapsulation matrix such as assisting in the survival of the microorganisms. The information gathered in this systematic mapping can be useful to guide researchers and industrial sectors on the development of innovative starch-based systems for microbial encapsulation.

Plasma-activated water (PAW) is liquid treated with plasma. This liquid develops a higher oxygen reduction potential, a lower pH, and conductivity due to the delivery of reactive species from plasma to water. In this article, we review the antimicrobial activity and other applications of PAW in various food products. We discuss the effects of PAW treatment parameters on microbial inactivation efficiency as well as the underlying mechanisms, pesticide dissipation and its degradation pathway, meat curing and strategies to improve the nitrite amount in PAW, enhancement of food functional characteristics, and seed germination and plant growth. Additionally, we highlight the effects of PAW on food quality attributes. We further introduce the synergistic interaction of PAW with other technologies. Finally, we provide an overview of future challenges that must be resolved in the application of PAW in the food industry.

The aim of this systematic review and meta-analysis was to determine which variables affect the viability of lactic acid bacteria (LAB) added to different types of refrigerated foods during the first 28 days. Scopus, ScienceDirect, PubMed and Cochrane Central Register of Reviews databases were searched from 1997 to April 2022. A total of 278 studies, which showed randomized and controlled experiments published in peer reviewed journals, were included. The viability of LAB in different moments during the storage process was synthesized as mean point estimate (MPE) via random-effects meta-analyses and the effect of multiple factors on the LAB´s viability was evaluated by multiple meta-regression. The meta-analysis showed that the decrease in LAB viability will be more abrupt the greater the initial dose. The physical structure of food may influence bacterial viability. Fruit was the type of product that most quickly lost viability. Co-culture of two or more species did not affect viability. Preservation methods had an unfavorable effect and prebiotics had a beneficial effect on bacterial viability. Viability was genus dependent. The data obtained in this study provide an overview of the factors to be taken into account for the design of new foods.

Tremendous progress in the inseparable relationships between probiotics and human health has enabled advances in probiotic functional foods. To ensure the vitality of sensitive probiotics against multiple harsh conditions, rising food-grade delivery systems for probiotics have been developed. This review gives a summary of recently reported delivery vehicles for probiotics, analyzes their respective merits and drawbacks and makes comparisons among them. Subsequently, the applications and future prospects are discussed. According to the types of encapsulating probiotics, food-grade delivery systems for probiotics can be classified into \"silkworm cocoons\" and \"spider webs\", which are put forward in this paper. The former, which surrounds the inner probiotics with the outer protective layers, includes particles, emulsions, beads, hybrid electrospun nanofibers and microcapsules. While hydrogels and bigels belong to the latter, which protects probiotics with the aid of network structures. The future prospects include preferable viability and stability of probiotics, co-delivery systems, targeted gut release of probiotics, delivery of multiple strains, more scientific experimental verification and more diversified food products, which will enlighten further studies on delivering probiotics for human health. Taken together, delivery vehicles for probiotics are-or will soon be-in the field of food science, with further applications under development.

Coronavirus disease (COVID-19) is a respiratory disease affecting many people and able to be transmitted through direct and perhaps indirect contact. Direct contact transmission, mediated by aerosols or droplets, is widely demonstrated, whereas indirect transmission is only supported by collateral evidence such as virus persistence on inanimate surfaces and data from other similar viruses. The present systematic review aims to estimate SARS-CoV-2 prevalence on inanimate surfaces, identifying risk levels according to surface characteristics. Data were obtained from studies in published papers collected from two databases (PubMed and Embase) with the last search on 1 September 2020. Included studies had to be papers in English, had to deal with coronavirus and had to consider inanimate surfaces in real settings. Studies were coded according to our assessment of the risk that the investigated surfaces could be contaminated by SARS-CoV-2. A meta-analysis and a metaregression were carried out to quantify virus RNA prevalence and to identify important factors driving differences among studies. Thirty-nine out of forty retrieved paper reported studies carried out in healthcare settings on the prevalence of virus RNA, five studies carry out also analyses through cell culture and six tested the viability of isolated viruses. Overall prevalences of SARS-CoV-2 RNA on high-, medium- and low-risk surfaces were 0.22 (CI95 [0.152-0.296]), 0.04 (CI95 [0.007-0.090]), and 0.00 (CI95 [0.00-0.019]), respectively. The duration surfaces were exposed to virus sources (patients) was the main factor explaining differences in prevalence.

Microbial extracellular polymeric substances (EPS) have a profound role in various wastewater treatment and reclamation processes, in which a variety of technologies are used for disinfection and microbial growth inhibition. These treatment processes can induce significant changes in the quantity and properties of EPS, and altered EPS could further adversely affect the wastewater treatment and reclamation system, including membrane filtration, disinfection, and water distribution. To clarify the effects of microbial inactivation approaches on EPS, these effects were classified into four categories: (1) chemical reactions, (2) cell lysis, (3) changing EPS-producing metabolic processes, and (4) altering microbial community. Across these different effects, treatments with free chlorine, methylisothiazolone, TiO2, and UV irradiation typically enhance EPS production. Among the residual microorganisms in EPS matrices after various microbial inactivation treatments, one of the most prominent is Mycobacterium. With respect to EPS properties, proteins and humic acids in EPS are usually more susceptible to treatment processes than polysaccharides. The affected EPS properties include changes in molecular weight, hydrophobicity, and adhesion ability. All of these changes can undermine wastewater treatment and reclamation processes. Therefore, effects on EPS quantity and properties should be considered during the application of microbial inactivation and growth inhibition techniques.