Production of Conjugated Linoleic Acid (CLA) by Lactiplantibacillus plantarum: A Review with Emphasis on Fermented Foods

The term Conjugated Linoleic Acid (CLA) refers generically to a class of positional and geometric conjugated dienoic isomers of linoleic acid. Among the isomers of linoleic acid cis9, trans11-CLA (c9, t11-CLA) and trans10, cis12-CLA (t10, c12-CLA) are found to be biologically active isomers, and they occur naturally in milk, dairy products and meat from ruminants. In addition, some vegetables and some seafoods have also been reported to contain CLA. Although the CLA levels in these natural sources are insufficient to confer the essential health benefits, anti-carcinogenic or anti-cancer effects are of current interest. In the rumen, CLA is an intermediate of isomerization and the biohydrogenation process of linoleic acid to stearic acid conducted by ruminal microorganisms. In addition to rumen bacteria, some other bacteria, such as Propionibacterium, Bifidobacterium and some lactic acid bacteria (LAB) are also capable of producing CLA. In this regard, Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) has demonstrated the ability to produce CLA isomers from linoleic acid by multiple enzymatic activities, including hydration, dehydration, and isomerization. L. plantarum is one of the most versatile species of LAB and the bacterium is widely used in the food industry as a microbial food culture. Thus, in this review we critically analyzed the literature produced in the last ten years with the aim to highlight the potentiality as well as the optimal conditions for CLA production by L. plantarum. Evidence was provided suggesting that the use of appropriate strains of L. plantarum, as a starter or additional culture in the production of some fermented foods, can be considered a critical factor in the design of new CLA-enriched functional foods.

Microbiology, flavor formation, and bioactivity of fermented soybean curd (furu): A review

Soybeans are an important plant-based food but its beany flavor and anti-nutritional factors limit its consumption. Fermentation is an effective way to improve its flavor and nutrition. Furu is a popular fermented soybean curd and mainly manufactured in Asia, which has been consumed for thousands of years as an appetizer because of its attractive flavors. This review first classifies furu products on the basis of various factors; then, the microorganisms involved in its fermentation and their various functions are discussed. The mechanisms for the formation of aroma and taste compounds during fermentation are also discussed; and the microbial metabolites and their bioactivities are analyzed. Finally, future prospects and challenges are introduced and further research is proposed. This information is needed to protect the regional characteristics of furu and to regulate its consistent quality. The current information suggests that more in vivo experiments and further clinical trials are needed to confirm its safety and the microbial community needs to be optimized and standardized for each type of furu to improve the production process.

Characterization and functional of four mutants of hydroxy fatty acid dehydrogenase from Lactobacillus plantarum p-8

In this study, the hydroxy fatty acid dehydrogenase CLA-DH from Lactobacillus plantarum p-8 and its four mutant variants were expressed in Escherichia coli Rosetta (DE3). UV spectrophotometry was employed to verify the catalytic power of the purified CLA-DH to convert ricinoleic acid into 12-oxo-cis-9-octadecenoic acid in the presence of oxidized nicotinamide adenine dinucleotide (NAD+). The optimum reaction temperature for CLA-DH was 45°C, with a maintained stability between 20°C and 40°C. The optimal pH for CLA-DH catalytic activity was 6.0-7.0, with a maintained stability at a pH range of 6.0-8.0. In addition, Fe3+ promoted enzyme activity, whereas Cu2+, Zn2+, and Fe2+ inhibited enzyme activity (P < 0.05). The Km, Vmax, Kcat, and Kcat/Km of CLA-DH were determined as 2.19 ± 0.34 μM, 2.06 ± 0.28 μM min-1, 2.00 ± 0.27 min-1, and 0.92 ± 0.02 min-1μM-1, respectively. Site-directed mutagenesis and molecular dynamics simulations demonstrated that both Tyr156 and Ser143 residues play significant roles in the catalysis of CLA-DH, and its solubility is affected by Lys160 and Asp63. Moreover, Gas chromatography determined that recombinant CLA-DH could be successfully applied to Conjugated linoleic acids production.

The Anti-Obesity Effects of Lemon Fermented Products in 3T3-L1 Preadipocytes and in a Rat Model with High-Calorie Diet-Induced Obesity

Lemon (Citrus limon) has antioxidant, immunoregulatory, and blood lipid-lowering properties. This study aimed to determine the effect of the lemon fermented product (LFP) which is lemon fermented with Lactobacillus OPC1 to prevent obesity. The inhibition of lipid accumulation in 3T3-L1 adipocytes is examined using a Wistar rat model fed a high-fat diet to verify the anti-obesity efficacy and mechanism of LFP. Here, it was observed that LFP reduced cell proliferation and inhibited the lipid accumulation (8.3%) of 3T3-L1 adipocytes. Additionally, LFP reduced body weight (9.7%) and fat tissue weight (25.7%) of rats; reduced serum TG (17.0%), FFA (17.9%), glucose (29.3%) and ketone body (6.8%); and increased serum HDL-C (17.6%) and lipase activity (17.8%). LFP regulated the mRNA expression of genes related to lipid metabolism (PPARγ, C/EBPα, SREBP-1c, HSL, ATGL, FAS, and AMPK). Therefore, LFP reduces body weight and lipid accumulation by regulating the mRNA expression of genes related to lipid metabolism. Overall, our results implicate LFP as a potential dietary supplement for the prevention of obesity.

Vaccinium bracteatum Thunb. fruit extract reduces high-fat diet-induced obesity with modulation of the gut microbiota in obese mice

Vaccinium bracteatum Thunb. fruits have been used as traditional food. This study investigated the effects of a polyphenol-rich Vaccinium bracteatum Thunb. fruit extract (VBTE) on obesity and obesity-related diseases in mice, and the potential role of the gut microbiota in the bioactivity of VBTE was also determined. Chemical constituents of the VBTE were analyzed by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS/MS). C57BL/6J mice (weighing 17.8-21.6 g) were fed a low-fat diet (LFD) or high-fat diet (HFD) with or without VBTE treatment for 14 weeks. The gut microbial changes were determined using 16S rRNA sequencing. Our results showed that VBTE mainly contains 36 kinds of polyphenols. VBTE reduced HFD-induced body weight gain by 33.42% (p < .05), steatosis scores by 56.25% (p < .05), and insulin resistance index by 51.49% (p < .05). Moreover, VBTE altered the composition of the gut microbiota. The correlation analysis indicated that Akkermansia, Alistipes, Bacteroides, Alloprevotella, Ruminiclostridium, Ruminiclostridium_9, and Rikenellaceae_RC9_gut_group were negatively correlated with serum lipids, glucose, and insulin, while Escherichia-Shigella was positively associated with these clinical indicators. In conclusion, VBTE supplement could reduce obesity and be a treatment option for obesity-related diseases by influencing the gut microbiota in mice. PRACTICAL APPLICATIONS: Plant extracts are widely used to treat obesity and related metabolic disorders. Polyphenols, the well-known natural antioxidants present in fruits, are consumed as a dietary supplement to prevent many diseases. Recent pharmacological studies have reported that Vaccinium bracteatum Thunb. fruits have many physiological functions, such as anti-proliferative, anti-inflammatory, and antidepressant-like effects. Despite these properties of Vaccinium bracteatum Thunb. fruits, their anti-obesity effect has not been studied to date. The findings of this study will support VBTE could be used as an important therapeutic application for preventing obesity and related metabolic diseases by modulating the gut microbiota.

Bioactivity of soy-based fermented foods: A review

For centuries, fermented soy foods have been dietary staples in Asia and, now, in response to consumer demand, they are available throughout the world. Fermentation bestows unique flavors, boosts nutritional values and increases or adds new functional properties. In this review, we describe the functional properties and underlying action mechanisms of soy-based fermented foods such as Natto, fermented soy milk, Tempeh and soy sauce. When possible, the contribution of specific bioactive components is highlighted. While numerous studies with in vitro and animal models have hinted at the functionality of fermented soy foods, ascribing health benefits requires well-designed, often complex human studies with analysis of diet, lifestyle, family and medical history combined with long-term follow-ups for each subject. In addition, the contribution of the microbiome to the bioactivities of fermented soy foods, possibly mediated through direct action or bioactive metabolites, needs to be studied. Potential synergy or other interactions among the microorganisms carrying out the fermentation and the host's microbial community may also contribute to food functionality, but the details still require elucidation. Finally, safety evaluation of fermented soy foods has been limited, but is essential in order to provide guidelines for consumption and confirm lack of toxicity.