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ABSTRACT In vitro gut fermentation models were firstly introduced in nutrition and applied microbiology research back in the 1990s. These models have improved greatly during time, mainly over the resemblance to the complexity of digestion stages, the replication of experimental conditions, the multitude of ecological parameters to assay. The state of the science is that the most competitive models shall include a complex gut microbiota, small working volumes, distinct interconnected compartments and rigorous bio-chemical and ecological settings, controlled by a computer, as well as a free-hands accessibility, not to contaminate the mock microbiota. These models are a useful tool to study the impact of a given diet compound, e.g. prebiotics, on the human gut microbiota. The principal application is to focus on the shift of the core microbial groups and selected species together with their metabolites, assaying their diversity, richness and abundance in the community over time. Besides, it is possible to study how a compound is digested, which metabolic pathways are triggered, and the type and quantity of microbial metabolites produced. Further prospective should focus on challenges with pathogens as well as on ecology of gut syndromes. In this minireview an updated presentation of the most used intestinal models is presented, basing on their concept, technical features, as well as on research applications. Intestinal in vitro models to study changes in the composition and metabolism of the gut microbiota in response to the diet.

Hemp seed bran (HB) is an industrial food byproduct that is generally discarded. Knowledge on the functional capabilities of HB is limited and it is not known the impact of HB on human colon microbiota, where vegetable fibers are metabolized. In this work, we investigated in depth the prebiotic potential of HB and HB protein extract hydrolyzed by alcalase (HBPA) in comparison to fructooligosaccharides (FOS) after human distal colonic fermentation using MICODE (multi-unit in vitro colon gut model). During the 24 h of fermentation, metabolomics (SPME GC/MS) and microbiomics (MiSeq and qPCR) analyses were performed. The results indicated that HBPA on a colonic fermentation had a higher prebiotic index than HB ( p  < 0.05), and slightly lower to that of FOS ( p  > 0.05). This feature was described and explained as HBPA colonic fermentation produces beneficial organic fatty acids ( e.g. Pentanoic and Hexanoic acids); reduces detrimental phenol derivates ( e.g. p -Cresol); produces bioactives VOCs ( e.g. Acetophenone or 4-Terpineol); increases beneficial bacteria ( e.g. 1.76 fold and 2.07 fold more of Bifidobacterium bifidum and Bacteroides fragilis , respectively) and limits opportunistic bacteria ( e.g. 3.04 fold and 2.07 fold less of Bilophila wadsworthia and Desulfovibrio , respectively). Our study evidenced the prebiotic role of HB and HBPA, and within the principles of OneHealth it valorizes a byproduct from the queen plant of sustainable crops as a food supplement.

Nowadays, the consumption of “free from” foods by non-specific consumers is increasing, partly due to a misperception of labels that make them seem healthier. These foods are formulated for consumers with allergies or diseases that limit their diet, and it is not known if there are more benefits than risks for healthy consumers. For example, there is no work investigating the interaction between lactose-free milk and the colonic microbiome of healthy individuals. To focus on the potential modulation of gut microbiota of healthy subjects by lactose-free milk, we performed an in vitro simulation of digestion and fermentation, integrating microbiomics and metabolomics approaches to study changes in gut microbiota populations and metabolite production. Results indicated that lactose-free and lactose-containing milk differently modulated colonic microbiota based on several microbiological indicators, including the reduction in Bifidobacteriaceae (approximately more than two times) and Lactobacillales and the reduction in the beneficial production of microbial compounds (approximately six times less acetic acid and two times less butanoic acid). Such features suggest that lactose-free milk increases the risk of dysbiosis in healthy subjects. Our work identifies the drivers of this dysbiosis among hundreds of molecules and microbes of the gut microbiota, assigning specific names and ecological niches for the first time. It employs an in vitro model, which represents a new standard for sustainable research and improves translatability. Our findings support the European Society for Clinical Nutrition and Metabolism (ESPEN) guidelines, which do not recommend the routine consumption of lactose-free diets in the absence of diagnosed intolerance.

Garlic (Allium sativum L.) is extensively recognized for its health-promoting effects and functional attributes, including antibacterial and anti-inflammatory activities. Additionally, the derived product of the industrial maturation process, known as black garlic, is famous for its functional properties. The novelty of the present work is to characterize the functional properties of domestically produced black garlic. In fact, this study examines the domestic maturation of fresh garlic bulbs into black garlic of two Italian varieties, focusing on microbial growth, antimicrobial properties, prebiotic activity, volatile organic compounds, mechanical resistance, brown intensity, pH, and Aw. Results show that domestic processes are microbiologically and chemically safe and generate black garlic products with functional attributes such as prebiotic activity and the presence of health-related bioactive compounds, also developing superior technological performance. These findings enhance the understanding of black garlic culinary practices, leveraging gastronomic preparations for the development of healthier and safer food products.

The European culinary culture relies on a wide range of fermented products of plant origin, produced mostly through spontaneous fermentation. Unfortunately, this kind of fermentations is difficult to standardize. Therefore, the use of commercial starter cultures is becoming common to achieve more stable, reproducible, and predictable results. Among plant-based fermentation processes, that of the red beet (Beta vulgaris L. var. conditiva) is scarcely described in the scientific literature. In this work, we compared different types of fermentation methods of beetroot and evaluated the processes’ micro-biological, physico-chemical, structural, and volatilome features. A multi-variate analysis was used to match the production of specific VOCs to each starter and to define the correlations between the process variables and volatilome. Overall, the results showed a successful lactic acid fermentation. The analysis of the volatilome clearly discriminated the metabolic profiles of the different fermentations. Among them, the sample fermented with the mixture was the one with the most complex and diversified volatilome. Furthermore, samples did not appear softened after fermentation. Although this work had its weaknesses, such as the limited number of samples and variety, it may pave the way for the standardization of artisanal fermentation procedures of red beetroot in order to improve the quality and safety of the derived food products.

Following the One Health principles in food science, the challenge to valorize byproducts from the industrial sector is open. Hemp (Cannabis sativa subsp. sativa) is considered an important icon of sustainability and as an alternative food source. Hemp seed bran, in particular, is a byproduct of industrial hemp seed processing, which is not yet valorized. The success, and a wider market diffusion of hemp seed for food applications, is hindered by its unpleasant taste, which is produced by certain compounds that generally overwhelm the pleasant bouquet of the fresh product. This research concerns the exploration of hemp seed bran through fermentation using beneficial lactobacilli, focusing on the sensorial and bioactive traits of the products when they are subjected to bacterial transformation. By studying of the aromatic profile formation during the fermentation process the aim was to modulate it in order to reduce off-odors without affecting the presence of healthy volatile organic compounds (VOCs). Applying multivariate analyses, it was possible to target the contribution of processing parameters to the generation of flavoring and bioactive compounds. To conclude, the fermentation process proposed was able to reduce unpleasant VOCs, whilst at the same time keeping the healthy ones, and it also improved nutritional quality, depending on time and bacterial starters. The fermentation proposed was a sustainable biotechnological approach that fitted perfectly with the valorization of hemp byproducts from the perspective of a green-oriented industrial process that avoids synthetic masking agents.

In this work, an aquaponic cultivation system for Lactuca sativa (L.) and Chicorium intybus (L.) was compared to a hydroponic one, focusing on the main microbial populations related to food safety and their volatile compounds (VOCs), concluding with Spearman correlations among the microbes and VOCs. Different sections of both systems were sampled at the end of the commercial development of the plants. Plants cultivated in aquaponics were in general more contaminated than those from hydroponics, while for the cultivation waters a higher contamination of the hydroponics than aquaponics system was unexpectedly observed. Furthermore, the chicory exhibited higher levels of all microbial groups compared to lettuce grown under the same cultivation system. The results obtained also showed correlations between the distribution of some VOCs and microbial groups in the phyllosphere, while some examples of positive correlations between 2-nonanone (a positive phytostimulant compound) and anaerobic bacilli of the rhizosphere in lettuce were reported. So far, multivariate analysis of VOCs was able to discriminate on the basis of varieties but not on the cultivation systems. In conclusion, the microbial characteristics of the two ecosystems depended both on plant variety and cultivation method but further studies will need to deeply investigate the variables influencing the microbial quality of vegetable foods obtained by aquaponics. On the other hand, the analysis of the VOCs was more related to the microbial community of each plant variety considered, whatever the cultivation system. In precision agriculture, metabolomics may represent an opportunity to study the holobiome and through it the interactions between plants and their microbial populations, to possibly provide for a tool to assess the microbiological quality of vegetable foods obtained by aquaponic systems.

The search for new fiber supplements that can claim to be “prebiotic” is expanding fast, as the role of prebiotics and intestinal microbiota in well-being has been well established. This work explored the prebiotic potential of a novel fiber plus D-Limonene supplement (FLS) in comparison to fructooligosaccharides (FOS) over distal colonic fermentation with the in vitro model MICODE (multi-unit in vitro colon gut model). During fermentation, volatilome characterization and core microbiota quantifications were performed, then correlations among volatiles and microbes were interpreted. The results indicated that FLS generated positive effects on the host gut model, determining: (i) eubiosis; (ii) increased abundance of beneficial bacteria, as Bifidobacteriaceae; (iii) production of beneficial compounds, as n-Decanoic acid; (iv) reduction in detrimental bacteria, as Enterobaceteriaceae; (v) reduction in detrimental compounds, as skatole. The approach that we followed permitted us to describe the prebiotic potential of FLS and its ability to steadily maintain the metabolism of colon microbiota over time. This aspect is two-faced and should be investigated further because if a fast microbial turnover and production of beneficial compounds is a hallmark of a prebiotic, the ability to reduce microbiota changes and to reduce imbalances in the productions of microbial metabolites could be an added value to FLS. In fact, it has been recently demonstrated that these aspects could serve as an adjuvant in metabolic disorders and cognitive decline.

Cold plasma (CP) is a non-thermal technology, successfully used to decontaminate and extend the shelf-life of various foods. However, CP can cause quality deterioration in sensitive matrices, such as fish products. This research aimed to evaluate the effect of CP treatment obtained using different gas mixtures (80% Ar/20% O2, or 80% N2/20% O2) with a surface dielectric barrier discharge (SDBD) on the decontamination of spoilage microflora, the main quality indices and the sensory acceptability of seabream (Spaurus aurata L.) fillets during refrigerated storage. At the beginning and at the end of the shelf life, lipid and protein oxidation indices and the fatty acid profile were evaluated. Results showed that, despite a low initial microbial decontamination (0.2–0.3 Log CFU/g), an inhibition of the growth of the main spoilage bacteria was observed resulting in an increase of the microbiological shelf life of around 40% for both treatments. Although a slight increase in lipid and protein oxidation was observed (up to around 5 mg MDA/kg and 4 nmol/mg of protein for TBARs and carbonyl content respectively), the sensory acceptability was higher for plasma treated samples, while the fatty acid profile was not affected and only a slight variation in the surface colour was observed (L* value increase by 3 points), confirming that CP could represent an interesting strategy to extend the shelf life of seafood products with minimal impact on quality and nutritional value.

Carob syrup, a traditional Mediterranean functional beverage obtained from Ceratonia siliqua (L.) pods, has been historically valued for its nutritional properties but is currently underutilized. This study compared the prebiotic potential of three handmade carob syrups produced by Tunisian women with commercial benchmarks from Italy, Greece and Cyprus. The prebiotic activity was evaluated by prebiotic scores, bifidogenic activity and volatilome characterization (SPME GC/MS) together with physicochemical and nutritional parameters. The results showed that Tunisian handmade products exhibited lower growth of pathogenic Escherichia coli compared to commercial samples. The prebiotic activity, tested against probiotic lactobacilli and bifidobacteria mixtures, showed a hierarchy of efficacy: fructo-oligosaccharides (FOSs) > Tunisian handmade products > Greek and Cypriot benchmarks > Italian benchmark. Volatilome analysis revealed about 40 compounds, mainly organic acids and aldehydes, with higher concentrations in handmade products. Positive correlations were found between prebiotic activity and short-chain fatty acids and n-hexadecanoic acid, while furfural showed negative correlations. The Tunisian artisanal products showed a higher prebiotic potential compared to the commercial counterparts, due to their higher content and diversity of organic acids. However, the presence of furfural in Tunisian products needs to be monitored due to potential toxicity concerns.