Insight into the mechanism of decreasing N-nitrosodimethylamine by Lactobacillus pentosus R3 in a model system

Production and transformation of biogenic amines in different food products by the metabolic activity of the lactic acid bacteria

Protein-rich diets often contain high quantities of biogenic amines (BAs), notably histamine and tyramine, which pose substantial health hazards owing to their toxicity. BAs are primarily produced by the microbial decarboxylation of free amino acids. Lactic acid bacteria (LAB) can either produce BAs using substrate-specific decarboxylase enzymes or degrade them into non-toxic compounds using amine-degrading enzymes such as amine oxidase and multicopper oxidase. Furthermore, LAB may inhibit BA-producing microbes by generating bioactive metabolites, including organic acids and bacteriocins. This paper thoroughly explores the processes underlying BA production and degradation in LAB, with a focus on the diversity of enzymes involved. Metabolic mapping of LAB strains at the genus and species levels reveals their involvement in BA metabolism, from production to degradation. The phylogenetic-based evolutionary relatedness of BA-producing and BA-degrading enzymes among LAB strains sheds light on their functional adaptability to various metabolic needs and ecological settings. These findings have significant practical implications for establishing better microbial management strategies in food production, particularly through strategically using starter or bioprotective cultures to reduce BA buildup. By highlighting the evolutionary and metabolic diversity of LAB, this review helps to optimize industrial fermentation processes, improve food safety protocols, and advance future research and innovation in BA management, ultimately protecting consumer health and supporting regulatory compliance.

Screening and Comparative Genomics of Probiotic Lactic Acid Bacteria from Bee Bread of Apis Cerana: Influence of Stevia and Stevioside on Bacterial Cell Growth and the Potential of Fermented Stevia as an Antidiabetic, Antioxidant, and Antifungal Agent

The purpose of this research is to identify and characterize lactic acid bacteria (LAB) species in bee bread produced by honey bees (Apis Cerana) in the east mountain area of Suzhou, China. We isolated three strains, Apilactobacillus kunkeei (S1), Lactiplantibacillus plantarum (S2), and Lacticaseibacillus pentosus (S3), with S2 producing the highest amount of lactic acid. Phylogenetic analysis indicated that these isolates, along with the type strain, formed a distinct sub-cluster within the LAB group. The strains exhibited non-hemolytic activity, lacked functional virulence factors, demonstrated high acid and bile tolerance, strong adhesion to intestinal cells, and antimicrobial activity against pathogens, collectively indicating their safety and high probiotic potential for therapeutic applications. Our studies demonstrated that S2 and S3 grew well in the presence of stevia leaf powder and steviosides, while S1 showed reduced growth and inhibitory effects. Importantly, the stevia-fermented strains exhibited strong probiotic potential along with significant antidiabetic, antioxidant, and antifungal properties in vitro. These findings highlight their potential applications in the food, feed, and pharmaceutical industries. Future research should focus on in vivo experiments to validate these results and evaluate compatibility among the strains before their application in functional foods.

Inhibition effect of non-contact biocontrol bacteria and plant essential oil mixture on the generation of N-nitrosamines in deli meat during storage

To reduce the risk of N-nitrosamines in deli meat products, this study formulated a novel non-contact N-nitrosamines inhibiting preservative IV (NIP-IV) consisting of biocontrol bacteria and plant essential oils (EOs) (Stenotrophomonas rhizophila SR-1 + Paenibacillus provencensis PP-2 + Bacillus subtilis CF-3+ cinnamon EO + grapefruit EO). Luncheon pork, spiced beef, and red sausage were taken as representatives of typical deli meat products and used to validate the effectiveness of NIP-IV in inhibiting N-nitroso dimethylamine (NDMA) production. The results showed that NIP-IV restrain protein degradation and lipid oxidation in deli meat products and effectively control microbial activity. Biogenic amines, such as phenethylamine, spermidine, cadaverine, and tyramine, were reduced. The conversion of nitrite to NDMA in deli meats was effectively inhibited by NIP-IV. Volatile organic compounds were the key to excellent NIP-IV non-contact preservation. Butyric acid, 3-methylbutanoic acid, benzaldehyde, d-limonene, and (E)-cinnamaldehyde were significantly negatively correlated with NDMA in deli meat products.

Bacterial diversity of stingless bee honey in Yunnan, China: isolation and genome sequencing of a novel acid-resistant Lactobacillus pentosus (SYBC-MI) with probiotic and L. tryptophan producing potential via millet fermentation

Stingless bee (Hymenoptera, Apidae, and Trigona) honey is a remarkable "miracle liquid" with a wide range of medical benefits for conditions including gastroenteritis, cataracts, and wound healing. Our study aimed to isolate, identify, and characterize acid-resistant Lactobacillus spp. from sour honey distributed in Yunnan, China. To assess the safety of an entirely novel Lactobacillus pentosus strain, S4 (OM618128), based on probiotic property evaluation and whole-genome sequencing analysis. A 16S rRNA gene high-throughput sequencing analysis showed that Lactobacillus was abundant at the genus level in sour honey. Seven Lactobacillus strains (viz. S1-7) were isolated from sour honey using a multiple-anaerobic culture enrichment method. One potential acid-resistant isolate, Lactobacillus sp. S4, was obtained after screening the seven Lactobacillus isolates, and it had the highest lactic acid production (17.62 g/L), followed by Lactobacillus sp. S3 (17.07 g/L). Phylogenetic and comparative analyses of conserved sequence regions have shown that all seven strains are phylogenetically located in the Lactobacillus pentosus sub-cluster. In L. pentosus SYBC-MI, there is a circular chromosome (3288615 bps) and 11,466 bps plasmids. GC content is 44.03%. The number of predicted genes is 3,129, with 16 rRNAs and 74 tRNAs present. During the fermentation of foxtail millet by seven Lactobacillus pentosus (S1-7) strains isolated from sour honey, a potential tryptophan accumulating isolate, Lactobacillus pentosus S4, was obtained, which could reach a maximum tryptophan content of 238.43 mgL-1 that is 1.80 times the initial tryptophan content in the fermentation broth. This strain has strong acid tolerance, salt tolerance, and fermentation acid production abilities. This strain degrades nitrite at a rate of over 99%, and it has high probiotic potential as well. This project has established a solid foundation for further exploring the excellent lactic acid bacteria in sour honey. It is also investigating the key taxa and their role in the environment. According to the results of our studies, these LAB isolates provide a lot of potential for use in the future, as a source of probiotics for human, animals, and starter cultures for food applications.

A comparative study of tea polyphenols and its palmitic acid-modified derivatives: their effects on the microbial ecosystem and biogenic amines in Chinese sausage

Control of biogenic amines (BAs) is important to guarantee the safety of sausage-like fermented meat products. This study investigated the influences of tea polyphenols (TP) and its lipophilic palmitic acid-modified derivatives, palmitoyl-TP (pTP) and palmitoyl-epigallocatechin gallate (pEGCG), on BAs and microbial ecosystem in Chinese sausages. TP, epigallocatechin gallate (EGCG), pTP, and pEGCG all reduced the formation of BAs and N-nitrosodimethylamine at 0.05% (g/g); yet, compared with TP and EGCG, the modified derivatives exhibited stronger action on BAs decreasing (P < 0.05), and pEGCG showed the highest effect (a reduction of total BAs from 376.22 to 168.98 mg/kg compared to control). The improved inhibitory effect of pTP and pEGCG should be attributed to their stronger dual-directional regulation of the bacterial and fungal communities during the natural fermentation of sausage. The modified pTP and pEGCG highly suppressed the growth of Staphylococcus, Candida, and Kurtzmaniella, all of which were positively correlated with BAs formation (all P < 0.05). However, pTP and pEGCG worked more effectively than the unmodified ones to promote Lactobacillus, Lactococcus, and Debaryomyces (all P < 0.05). The results above are significant for the application of palmitoyl-TP and similar TP derivatives in meat products in consideration of food safety.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05717-z.

Changes in N-nitrosamines, residual nitrites, lipid oxidation, biogenic amines, and microbiota in Chinese sausages following treatment with tea polyphenols and their palmitic acid–modified derivatives

This study aimed to investigate the effects of tea polyphenol (TP), epigallocatechin gallate (EGCG), and their palmitic acid-modified derivatives palmitoyl-TP (pTP) and palmitoyl-EGCG (pEGCG) on the accumulation of N-nitrosamine and biogenic amines (BAs), residual nitrites, and lipid oxidation in Chinese sausages. The microorganisms, color, and texture properties of sausages were evaluated. TP, EGCG, pTP, or pEGCG significantly inhibited the accumulation of N-nitrosodimethylamine (NDMA) and BAs, residual nitrites, and lipid oxidation, but enhanced the redness, hardness, and chewiness of sausages. The concentration of NDMA in sausages was reduced by 58.11%, 63.51%, 36.49%, and 44.59%, respectively, after treatment with TP, EGCG, pTP, and pEGCG. Both EGCG and pEGCG exhibited excellent inhibitory effects on the predominant BAs, including putrescine, tyramine, cadaverine, histamine, and 2-phenylethylamine. Palmitoyl-EGCG was found to be the strongest inhibitor of lipid oxidation. Besides, the four antioxidants weakly affected the population of total aerobic bacteria and lactic acid bacteria but totally suppressed the growth of undesirable Enterobacteriaceae. The principal component and correlation analyses proved that BAs, nitrites, lipid oxidation, and microbiota were responsible for the formation of NDMA. The results indicated that palmitic acid-modified TPs and similar derivatives might serve as potential preservatives to improve the safety and quality of fermented meat products.

A Review on the Role of Lactic Acid Bacteria in the Formation and Reduction of Volatile Nitrosamines in Fermented Sausages

Nitrosamines are N-nitroso compounds with carcinogenic, mutagenic and teratogenic properties. These compounds could be found at certain levels in fermented sausages. Fermented sausages are considered to be a suitable environment for nitrosamine formation due to acid formation and reactions such as proteolysis and lipolysis during ripening. However, lactic acid bacteria (spontaneous or starter culture), which constitute the dominant microbiota, contribute significantly to nitrosamine reduction by reducing the amount of residual nitrite through nitrite degradation, and pH decrease has an important effect on the residual nitrite amount as well. These bacteria also play an indirect role in nitrosamine reduction by suppressing the growth of bacteria that form precursors such as biogenic amines. In recent years, research interest has focused on the degradation or metabolization of nitrosamines by lactic acid bacteria. The mechanism by which these effects are seen has not been fully understood yet. In this study, the roles of lactic acid bacteria on nitrosamine formation and their indirect or direct effects on reduction of volatile nitrosamines are discussed.

Combined Effect of High-Pressure Processing with Spice Extracts on Quality of Low-Salt Sausage during Refrigerated Storage

The study evaluated the combined effect of high-pressure processing (HPP) and spice extracts on low-salt sausages during refrigerated storage. Physicochemical and microbiological characteristics of the sausages were determined. HPP treatment increased the thiobarbituric acid reactive substances (TBARS) value and the carbonyl content of the samples (p < 0.05), which meant lipid and protein oxidation was accelerated. Adding clove and cinnamon extracts can retard the oxidation caused by HPP (p < 0.05). The pH of the sausages treated with both the spice extracts and HPP maintained a higher pH value during the storage (p > 0.05). Compared with the samples treated with HPP or with the spice extracts alone, the combined treatment observably inhibited the growth of spoilage bacteria (p < 0.05) and improved the microbial community. The results demonstrated that the use of clove and cinnamon extracts in conjunction with HPP improved the storage quality and prolonged the shelf-life of the low-salt sausages. Thus, the combined use of spice extracts and HPP can be developed as a promising way to preserve low-salt meat products.

The function and mechanism of lactic acid bacteria in the reduction of toxic substances in food: a review

N-nitrosamines, heterocyclic amines, polycyclic aromatic hydrocarbons, biogenic amines, and acrylamide are widely distributed and some of the most toxic substances detected in foods. Hence, reduction of these substances has attracted worldwide attention. Lactic acid bacteria (LAB) inoculation has been found to be an effective way to reduce these toxic substances. In this paper, the reduction of toxic substances by LAB and its underlying mechanisms have been described through the review of recent studies. LAB aids this reduction via different mechanisms. First, it can directly decrease these harmful substances through adsorption or degradation. Peptidoglycans on the cell wall of LAB can bind to heterocyclic amines, acrylamide, and polycyclic aromatic hydrocarbons. Second, LAB can indirectly decrease the content of toxic substances by reducing their precursors. Third, antioxidant properties of LAB also contribute to the reduction in toxic substances. Finally, LAB can suppress the growth of amino acid decarboxylase-positive bacteria, thus reducing the accumulation of biogenic amines and N-nitrosamines. Therefore, LAB can contribute to the decrease in toxic substances in food and improve food safety. Further research on increasing the reduction efficiency of LAB and deciphering the mechanisms at a molecular level needs to be carried out to obtain the complete picture.