Selected probiotic lactic acid bacteria isolated from fermented foods for functional milk production: Lower cholesterol with more beneficial compounds

Functional roles and engineering strategies to improve the industrial functionalities of lactic acid bacteria during food fermentation

In order to improve the flavor profiles, food security, probiotic effects and shorten the fermentation period of traditional fermented foods, lactic acid bacteria (LAB) were often considered as the ideal candidate to participate in the fermentation process. In general, LAB strains possessed the ability to develop flavor compounds via carbohydrate metabolism, protein hydrolysis and amino acid metabolism, lipid hydrolysis and fatty acid metabolism. Based on the functional properties to inhibit spoilage microbes, foodborne pathogens and fungi, those species could improve the safety properties and prolong the shelf life of fermented products. Meanwhile, influence of LAB on texture and functionality of fermented food were also involved in this review. As for the adverse effect carried by environmental challenges during fermentation process, engineering strategies based on exogenous addition, cross protection, and metabolic engineering to improve the robustness and of LAB were also discussed in this review. Besides, this review also summarized the potential strategies including microbial co-culture and metabolic engineering for improvement of fermentation performance in LAB strains. The authors hope this review could contribute to provide an understanding and insight into improving the industrial functionalities of LAB.

Gamma-aminobutyric acid as a potential postbiotic mediator in the gut-brain axis

Gamma-aminobutyric acid (GABA) plays a crucial role in the central nervous system as an inhibitory neurotransmitter. Imbalances of this neurotransmitter are associated with neurological diseases, such as Alzheimer's and Parkinson's disease, and psychological disorders, including anxiety, depression, and stress. Since GABA has long been believed to not cross the blood-brain barrier, the effects of circulating GABA on the brain are neglected. However, emerging evidence has demonstrated that changes in both circulating and brain levels of GABA are associated with changes in gut microbiota composition and that changes in GABA levels and microbiota composition play a role in modulating mental health. This recent research has raised the possibility that GABA may be a potent mediator of the gut-brain axis. This review article will cover up-to-date information about GABA-producing microorganisms isolated from human gut and food sources, explanation why those microorganisms produce GABA, food factors inducing gut-GABA production, evidence suggesting GABA as a mediator linking between gut microbiota and mental health, including anxiety, depression, stress, epilepsy, autism spectrum disorder, and attention deficit hyperactivity disorder, and novel information regarding homocarnosine-a predominant brain peptide that is a putative downstream mediator of GABA in regulating brain functions. This review will help us to understand how the gut microbiota and GABA-homocarnosine metabolism play a significant role in brain functions. Nonetheless, it could support further research on the use of GABA production-inducing microorganisms and food factors as agents to treat neurological and psychological disorders.

Biodegradation of Cholesterol by Enterococcus faecium YY01

Cholesterol (CHOL) is one of the risk factors causing the blockage of the arterial wall, atherosclerosis, coronary heart disease, and other serious cardiovascular diseases. Here, a promising bacterial strain for biodegrading CHOL was successfully isolated from the gut of healthy individuals and identified as Enterococcus faecium YY01 with an analysis of the 16S rDNA sequence. An initial CHOL of 1.0 g/L was reduced to 0.5 g/L in 5 days, and glucose and beef extract were found to be optimal carbon and nitrogen sources for the rapid growth of YY01, respectively. To gain further insight into the mechanisms underlying CHOL biodegradation, the draft genome of YY01 was sequenced using Illumina HiSeq. Choloylglycine hydrolase, acyltransferase, and alkyl sulfatase was encoded by gene0586, gene1890, and gene2442, which play crucial roles in converting 3α, 7α, 12α-trihydroxy-5β-choranic acid to choline-CoA and then choline-CoA to bile acid. Notably, choloylglycine hydrolase was closely related to the biosynthesis of both primary and secondary bile acid. The findings of this study provide valuable insights into the metabolism pathway of CHOL biodegradation by YY01 and offer a potential avenue for the development of bacterioactive drugs against hypercholesterolemia.

The Impacts of Acidophilic Lactic Acid Bacteria on Food and Human Health: A Review of the Current Knowledge

The need to improve the safety/quality of food and the health of the hosts has resulted in increasing worldwide interest in acidophilic lactic acid bacteria (LAB) for the food, livestock as well as health industries. In addition to the use of acidophilic LAB with probiotic potential for food fermentation and preservation, their application in the natural disposal of acidic wastes polluting the environment is also being investigated. Considering this new benefit that has been assigned to probiotic microorganisms in recent years, the acceleration in efforts to identify new, efficient, promising probiotic acidophilic LAB is not surprising. One of these effots is to determine both the beneficial and harmful compounds synthesized by acidophilic LAB. Moreover, microorganisms are of concern due to their possible hemolytic, DNase, gelatinase and mucinolytic activities, and the presence of virulence/antibiotic genes. Hence, it is argued that acidophilic LAB should be evaluated for these parameters before their use in the health/food/livestock industry. However, this issue has not yet been fully discussed in the literature. Thus, this review pays attention to the less-known aspects of acidophilic LAB and the compounds they release, clarifying critical unanswered questions, and discussing their health benefits and safety.

The Expression Levels of Genes Responsible for the Enzymatic Activity of Bile Salt Hydrolase (BSH) and the Relationship of Cholesterol Assimilation in L. plantarum and L. paracasei

The bile salt hydrolase (BSH) activity is responsible for the cholesterol-lowering effect of the probiotic strains. The present study aimed to investigate the relationship between bsh gene-expression (GE) levels responsible for the BSH activity and the parameters of bile salt resistance of different Lactobacillaceae species. Accordingly, 11 Lactobacillaceae family strains with high cholesterol assimilation ratio (49.21-68.22%) determined by the o-phthalaldehyde method selected from 46 Lactobacillaceae species was evaluated for their features including acid tolerance, bile tolerance, and BSH activity. All tested strains survived at pH 2 medium and 0.3% (w/v) bile salt and showed positive BSH activity for glycocholic acid (GCA) and taurocholic acid (TCA). BSH gene expression was performed to provide clear information and to identify the key genes responsible for BSH activity. bsh3 genes were found highest GE level (P < 0.05) in Lactiplantibacillus plantarum and Lacticaseibacillus paracasei strains. The results showed that high cholesterol assimilation ratio were closely correlated with BSH activity and the parameters of bile salt resistance. The results of this study will support the development of a new approach based on phenotypic and genetic analysis to determine the bile salt parameters. The study will be useful for the selection of Lactobacillus strains with high bile salt resistance.

In-vitro evaluation of the probiotic potential and the fermentation profile of Pediococcus and Enterococcus strains isolated from Moroccan camel milk

The promotion of human health through natural approaches like functional foods and probiotics is in high demand. The medicinal plants are the major feed of Moroccan dromedary, which improves the functional properties of their milk. A few studies have reported the probiotic and functional aptitudes of lactic acid bacteria (LAB) of this milk. In this context, our study aimed to identify LAB isolated from Moroccan raw camel milk and investigate their probiotic features and their fermentation profile. The molecular identification of twelve isolates indicated that they belong to Pediococcus pentosaceus, Enterococcus faecium, and Enterococcus durans. All LAB strains displayed high tolerance to gastrointestinal conditions (survival rate of 31.85-96.52% in pH 2.5, 35.23-99.05% in 0.3 bile salts, and 26.9-90.96% in pepsin), strong attachment abilities (auto-aggregation and hydrophobicity ranged from 28.75 to 95.9% and from 80.47 to 96.37%, respectively), and high co-aggregation ability with pathogenic bacteria. Importantly, they did not present antibiotic resistance or hemolytic activity. Our LAB strains demonstrated antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Bacillus subtilis, and Salmonella enterica. Moreover, they could acidify cow milk (ΔpH of 2.55 after 24 h) and improve its antioxidant ability (inhibition of 36.77% of DPPH). Based on the multivariate analysis, Pediococcus pentosaceus Pd24, Pd29, Pd38, Enterococcus faecium Ef18, and Enterococcus durans Ed22 were selected as the most promising probiotics. Therefore, we propose that Pediococcus pentosaceus isolated from camel milk could be used as potential probiotic strains and/or starter cultures in functional milk fermentation.

Oral administration of Bacillus cereus GW-01 alleviates the accumulation and detrimental effects of β-cypermethrin in mice

Pyrethroid insecticides negatively affect feed conversion, reproductive fitness, and food safety in exposed animals. Although probiotics have previously been widely studied for their effect on gut health, comparatively little is known regarding the efficacy of probiotic administration in specifically reducing pesticide toxicity in mice. We demonstrated that oral administration of a β-cypermethrin (β-CY)-degrading bacterial strain (Bacillus cereus GW-01) to β-CY-exposed mice reduced β-CY levels in the liver, kidney, brain, blood, lipid, and feces (18%-53%). Additionally, co-administration of strain GW-01 to β-CY-exposed mice reduced weight loss (22%-31%) and improved liver function (15%-19%) in mice. Additionally, mice receiving GW-01 had near-control levels of numerous β-CY-affected gut microbial taxa, including Muribaculaceae, Alloprevotella, Bacteroides, Dubosiella, and Alistipes. The survival and β-CY biosorption of GW-01 in simulated gastrointestinal fluid conditions were significantly higher than E. coli. These results suggested that GW-01 can reduce β-CY accumulation and alleviate the damage in mice. This study is the first to demonstrate that a probiotic strain can reduce the toxicity of β-CY in mice.

Phytochemical Composition and Bioactivities of Aqueous Extract of Rambutan (Nephelium lappaceum L. cv. Rong Rian) Peel

Thailand is one of the leading exporting countries of rambutan and rambutan peels are considered as a biological waste. In this study, rambutan (Nephelium lappaceum L. cv. Rong Rian) peel extracts (RPE) obtained by water extraction were analyzed for their phytochemical composition, antibacterial and antioxidant activities, and cytotoxicity. The bioactive compounds in RPE identified by GC-MS were mome inositol (35.99 mg/g), catechol (29.37 mg/g), 5-hydroxymethylfurfural (5.69 mg/g), 2-pentenal, (E)-(5.22 mg/g), acetic acid (3.69 mg/g), 1,2,3-propanetriol (3.67 mg/g), 2-furan-carboxaldehyde (2.66 mg/g), and other compounds. FT-IR analysis confirmed the presence of alcohol and phenol in the extract. Antibacterial activities of RPE against food pathogenic and spoilage bacteria showed that RPE could inhibited Bacillus subtilis, B. cereus, Staphylococcus aureus, Vibrio cholerae, V. parahaemolyticus, Pseudomonas aeruginosa, and P. fluorescens, with MIC values ranging between 1024 and 8192 µg/mL. The extract also showed antioxidant properties, as determined by DPPH and ABTS assays. The cytotoxicity analysis after 72 h of treatment showed the IC₅₀ values at 194.97 ± 4.87, 205.92 ± 2.55, and 94.11 ± 1.33 µg/mL for L929, Vero, and MCF-7 cell lines, respectively. Therefore, this study provided a basis of knowledge of rambutan peels as an excellent source of natural bioactive compounds for various applications.

Photosensitized oxidation of cholesterol and altered oxysterol levels in sour cream: Effects of addition of cucumber pickles

The aim of this research was to examine whether sour cream (18% fat) is an exogenous source of oxysterols and whether it is possible to improve its antioxidative properties and to modulate cholesterol transformation by adding cucumber. To determine whether cucumber modifies the properties of sour cream, fresh cucumber or cucumber pickle (pH 3.3; 1.5% lactic acid) was added in an amount of 20%. The sour cream samples were then stored under light (450 lx, 590 cd, 120 lm) for 3 wk. After storage, the addition of the cucumber pickle increased total mesophilic aerobic bacteria from 7.5 to 9.3 log cfu/g and increased the l-lactic acid content from 6.1 to 9.7 g/L. The total conjugated linoleic acid content in sour cream with cucumber pickle also increased to 4.5 mg/g fat after storage, whereas the cholesterol content decreased to 3.44 g/kg fat. Importantly, with the addition of cucumber pickle, the total content of cholesterol oxidization products (COP) did not change after storage (1.7 mg/kg fat). By contrast, the total COP content in the control sour cream sample increased from 1.7 to 7.3 mg/kg fat over 3 wk of storage. The dominant COP before and after storage was 7β-hydroxycholesterol. Thus, despite exposure to light, adding cucumber pickle to sour cream modulates cholesterol transformation and effectively inhibits the formation of oxysterols.

Genotyping of Probiotic Lactobacilli in Nigerian Fermented Condiments for Improved Food Safety

BACKGROUND: Plant-based naturally fermented condiments usually result in poor quality products with various bacteria and fungi contaminants. Previous reports suggested the use of starter cultures from previously fermented condiments in fermentation processes to ensure health-promoting benefits, improved quality, shelf life, and organoleptic properties for the achievement of healthy nutrition, safe, and quality food. AIM: This study aimed to genotype potential lactobacilli from locally fermented condiments for improved food safety. METHODS: The lactobacilli colonies isolated from fermented condiments purchased from food markets in Southwest Nigeria were profiled for probiotic activities, hemolytic activities, antibiotics susceptibility, and inhibitory activities against food pathogens. Interesting probiotic lactobacilli were identified using 16S rRNA gene sequencing and evaluated for phylogenetic relatedness with other globally reported probiotic lactobacilli. RESULTS: Lactobacillus species which expressed significant probiotics, γ-hemolysis, anti-spoilage, and anti-listerial activities (P < 0.05) with tolerable safety profiles were identified as Lactiplantibacillus plajomi YD001 (MW280136), Lactiplantibacillus plantarum YD002 (MW280139), L. plantarum YD003 (MW280137), and Lacticaseibacillus paracasei YD004 (MW280138) possessed 50.75, 50.61, 50.75, and 52.54 mol% DNA G+C contents, respectively. The species clustered into different phylogroups with high clonal relatedness with other potential lactobacilli meta-data (≥96.80%) obtained from the public repository. CONCLUSION: Obtained genotyped Lactobacillus species are potential starter cultures for improved fermentation processes, control of food pathogens, and spoilage organisms.

Biotechnology for carbon capture and fixation: Critical review and future directions

To mitigate the growing threat of climate change and develop novel technologies that can eliminate carbon dioxide, the most abundant greenhouse gas derived from the flue gas stream of the fossil fuel-fired power stations, is momentous. The development of carbon capture and sequestration-based technologies may play a significant role in this regard. Carbon fixation mostly occurs by photosynthesizing plants as well as photo and chemoautotrophic microbes that turn the atmospheric carbon dioxide into organic materials via their enzymes. Biofuel can offer a sustainable solution for carbon mitigation. The pragmatic implementation of biofuel production processes is neither cost-effective nor has been proven safe over the long term. Searching for ways to enhance biofuel generation by the employment of genetic engineering is vital. Carbon biosequestration can help to curb the greenhouse effect. In addition, new genomic approaches, which are able to use gene-splicing biotechnology techniques and recombinant DNA technology to produce genetically modified organisms, can contribute to improvement in sustainable and renewable biofuel and biomaterial production from microorganisms. Biopolymers, Biosurfactants, and Biochars are suggested as sustainable future trends. This study aims to pave the way for implementing biotechnology methods to capture carbon and decrease the demand and consumption of fossil fuels as well as the emissions of greenhouse gases. Having a better image of microorganisms' potential role in carbon capture and storage can be prolific in developing powerful techniques to reduce CO₂ emissions.