Bioactive natural products: facts, applications, and challenges

License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Today, there are a strong debate and interest regarding the safety aspects of chemical preservatives addedwidely inmany food products to prevent mainly growth of spoilage and pathogenic microbes. Synthetic compounds are considered responsible for carcinogenic and teratogenic attributes and residual toxicity. To avoid the aforementioned problems, consumers and authorities have increased pressure on food manufacturers to substitute the harmful artificial additives with alternative, more effective, nontoxic, and natural sub-stances. In this context, the use of natural compounds with antimicrobial action presents an intriguing case. Natural antioxidants also demonstrate a wide range of biological and pharmacological activities and are considered to have bene

COVID-19 on the spectrum: a scoping review of hygienic standards

The emergence of COVID-19 in Wuhan, China, rapidly escalated into a worldwide public health crisis. Despite numerous clinical treatment endeavors, initial defenses against the virus primarily relied on hygiene practices like mask-wearing, meticulous hand hygiene (using soap or antiseptic solutions), and maintaining social distancing. Even with the subsequent advent of vaccines and the commencement of mass vaccination campaigns, these hygiene measures persistently remain in effect, aiming to curb virus transmission until the achievement of herd immunity. In this scoping review, we delve into the effectiveness of these measures and the diverse transmission pathways, focusing on the intricate interplay within the food network. Furthermore, we explore the virus's pathophysiology, considering its survival on droplets of varying sizes, each endowed with distinct aerodynamic attributes that influence disease dispersion dynamics. While respiratory transmission remains the predominant route, the potential for oral-fecal transmission should not be disregarded, given the protracted presence of viral RNA in patients' feces after the infection period. Addressing concerns about food as a potential viral vector, uncertainties shroud the virus's survivability and potential to contaminate consumers indirectly. Hence, a meticulous and comprehensive hygienic strategy remains paramount in our collective efforts to combat this pandemic

Chemical Composition and Evaluation of the Biological Properties of the Essential Oil of the Dietary Phytochemical Lippia citriodora

The aim of the study was to characterize the chemical composition and biological properties of the essential oil from the plant Lippia citriodora grown in Greece. The essential oil volatiles were analyzed by gas chromatography–mass spectrometry GC-MS indicating citral as the major component. Τhe antimicrobial properties were assayed using the disk diffusion method and the minimum inhibitory and non-inhibitory concentration values were determined. Listeria monocytogenes, Staphylococcus epidermidis, Staphylococcus aureus, Saccharomyces cerevisiae, and Aspergillus niger were sensitive to Lippia citriodora oil, but not Escherichia coli, Salmonella Enteritidis, Salmonella typhimurium, and Pseudomonas fragi. Adversely, all microbes tested were sensitive to citral. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays were used to assess direct antioxidant activity, which proved to be weak for both agents, while comet assay was utilized to study the cytoprotective effects against H2O2-induced oxidative damage in Jurkat cells. Interestingly, the oil showed a more profound cytoprotective effect compared to citral. The antiproliferative activity was evaluated in a panel of cancer cell lines using the sulforhodamine B (SRB) and 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-S-(phenylamino) carbonyl-2-tetrazolium hydroxide (XTT) assays and both agents demonstrated potent antiproliferative activity with citral being more cytotoxic than the oil. Taken together, the essential oil of Lippia citriodora and its major component, citral, exert diverse biological properties worthy of further investigation

In vitro study on the cell adhesion ability of immobilized lactobacilli on natural supports

The aim of the present study was to investigate the effect of probiotic immobilization onto wheat grains, both wet and freeze dried, on the adhesion properties of the probiotic cells and make comparisons with wet and freeze dried free cells. Lactobacillus casei ATCC 393 and Lactobacillus plantarum NCIMB 8826 were used as model probiotic strains. The results showed satisfactory adhesion ability of free cells to a monolayer of Caco-2 cells (> 1000 CFU/100 Caco-2 cells for wet cells). Cell immobilization resulted in a significant decrease in adhesion, for both wet and freeze dried formulations, most likely because immobilized cells did not have direct access to the Caco-2 cells, but it still remained in adequate levels (> 100 CFU/100 Caco-2 cells for wet cells). No clear correlation could be observed between cell adhesion and the hydrophobicity of the bacterial cells, measured by the hexadecane adhesion assay. Most notably, immobilization enhanced the monolayer integrity of Caco-2 cells, demonstrated by a more than 2-fold increase in transepithelial electrical resistance (TEER) compared to free cells. SEM micrographs ascertained the adhesion of both immobilized and free cells to the brush border microvilli. Finally, the impact of the food matrix on the adhesion properties of probiotic bacteria and on the design of novel functional products is discussed

Nano-Tubular Cellulose for Bioprocess Technology Development

Delignified cellulosic material has shown a significant promotional effect on the alcoholic fermentation as yeast immobilization support. However, its potential for further biotechnological development is unexploited. This study reports the characterization of this tubular/porous cellulosic material, which was done by SEM, porosimetry and X-ray powder diffractometry. The results showed that the structure of nano-tubular cellulose (NC) justifies its suitability for use in “cold pasteurization” processes and its promoting activity in bioprocessing (fermentation). The last was explained by a glucose pump theory. Also, it was demonstrated that crystallization of viscous invert sugar solutions during freeze drying could not be otherwise achieved unless NC was present. This effect as well as the feasibility of extremely low temperature fermentation are due to reduction of the activation energy, and have facilitated the development of technologies such as wine fermentations at home scale (in a domestic refrigerator). Moreover, NC may lead to new perspectives in research such as the development of new composites, templates for cylindrical nano-particles, etc

Wine making using immobilized cells on fruits

The biocatalysts prepared by immobilization of Saccharomyces cerevisiae strain AXAZ-1 on apple and quince pieces were studied during batch and continuous wine-making. The immobilized cells showed an important operational stability without any decrease of their activity even at low temperatures. Fermentation times were lower than those required for the natural fermentation of grape must, while wine productivities reported during the continuous process were much higher than those reported during batch fermentations. The produced wines were at very good quality containing low concentrations of higher alcohols and methanol. They were characterized as special types of wines with a distinctive aromatic potential and a pleasant taste. The comparative study of the viability of baker’s yeast cells immobilized on kissins, γ-alumina and apple pieces showed that the immobilized biocatalysts were able to ferment after remaining for high time intervals (at least 6 months) at 30°C after the end of a fermentation batch. No significant reduction in the fermentation activity or change in the volatile by-product composition of the produced wines was reported.Οι ακινητοποιημένοι βιοκαταλύτες που παρασκευάστηκαν με ακινητοποίηση κυττάρων του στελέχους ΑΧΑΖ-1 του Saccharomyces cerevisiae σε κομμάτια μήλου και σε κομμάτια κυδωνιού χρησιμοποιήθηκαν για παραγωγή κρασιού μέσω επαναλαμβανόμενων παρτίδων ζύμωσης αλλά και μέσων συνεχούς διεργασίας. Τα ακινητοποιημένα κύτταρα έδειξαν σημαντική λειτουργική σταθερότητα, χωρίς να παρατηρηθεί μείωση της δραστικότητας ακόμα σε χαμηλές θερμοκρασίες ζύμωσης. Οι χρόνοι ζύμωσης ήταν πολύ μικρότεροι από αυτούς που απαιτούνται για τη φυσική παραδοσιακή ζύμωση του γλεύκους, ενώ οι παραγωγικότητες κρασιού ήταν υψηλότεροι κατά τη συνεχή διεργασία συγκρινόμενες με τις αντίστοιχες των επαναλαμβανόμενων παρτίδων ζύμωσης. Τα κρασιά που παράχθηκαν ήταν πολύ καλής ποιότητας, περιείχαν πολύ χαμηλές συγκεντρώσεις ανώτερων αλκοολών και μεθανόλης και χαρακτηρίστηκαν ως νέου τύπου κρασιά, με ιδιαίτερα, χαρακτηριστικό άρωμα και ευχάριστη γεύση. Η συγκριτική μελέτη της βιωσιμότητας κυττάρων ζύμης αρτοποιίας ακινητοποιημένων σε κίσσηρη, γ-αλουμίνα και μήλο, έδειξε ότι οι ακινητοποιημένοι βιοκαταλύτες είναι δυνατόν να παραμείνουν στους 30°C μετά το τέλος της ζύμωσης για μεγάλο χρονικό διάστημα (τουλάχιστον 6 μηνών), χωρίς να παρατηρηθεί σημαντική μείωση της δραστικότητας η μεταβολή και σύσταση των πτητικών παραπροϊόντων των χρηστών

Food Preservation: Challenges and Efforts for the Future

Microbial hazards and food oxidation have acquired substantial economical, ethical and legal importance in the food industry [...

Immobilization of microbial cells for alcoholic and malolactic fermentation of wine and cider

Wine-or cider-making is highly associated with biotechnology owing to the traditional nature of must fermentation. Nowadays, there have been considerable developments in wine-or cider-making techniques affecting all phases of wine or cider production, but more importantly, the fermentation process. It is well-known that the transformation of grape must by microbial activity results in the production of wine, and the fermentation of apples (or sometimes pears) in the production of cider. In this process, a variety of compounds affecting the organoleptic profile of wine or cider are synthesized. It is also common sense that in wine-or cider-making, the main objective is to achieve an adequate quality of the product. The technological progress and the improved quality of the wines or ciders have been associated with the control of technical parameters. Herein, cell immobilization offers numerous advantages, such as enhanced fermentation productivity, ability for cell recycling, application of continuous configurations, enhanced cell stability and viability, and improvement of quality (Margaritis and Merchant 1984; Stewart and Russel 1986; Kourkoutas et al. 2004a). The objective of the present chapter is to analyze and assess data on the impact of immobilization technologies of viable microbial cells on the alcoholic and malolactic fermentation (MLF) of wine and cider. The immobilized biocatalysts are evaluated for their scale-up ability and their potential future impact in industrial application is highlighted and assessed. Handicaps associated with maintenance of cell viability and fermentation efficiency during preservation and storage, constraining the industrial use of immobilized cell systems are discussed