Antibacterial Activities of Fermented Plant Beverages Collected in Southern Thailand

Screening of GABA-Producing Lactic Acid Bacteria from Thai Fermented Foods and Probiotic Potential of Levilactobacillus brevis F064A for GABA-Fermented Mulberry Juice Production

Gamma-aminobutyric acid (GABA), the inhibitory neurotransmitter, can be naturally synthesized by a group of lactic acid bacteria (LAB) which is commonly found in rich carbohydrate materials such as fruits and fermented foods. Thirty-six isolates of GABA-producing LAB were obtained from Thai fermented foods. Among these, Levilactobacillus brevis F064A isolated from Thai fermented sausage displayed high GABA content, 2.85 ± 0.10 mg/mL and could tolerate acidic pH and bile salts indicating a promising probiotic. Mulberry (Morus sp.) is widely grown in Thailand. Many mulberry fruits are left to deteriorate during the high season. To increase its value, mulberry juice was prepared and added to monosodium glutamate (MSG), 2% (w/v) prior to inoculation with 5% (v/v) of L. brevis F064A and incubated at 37 °C for 48 h to obtain the GABA-fermented mulberry juice (GABA-FMJ). The GABA-FMJ obtained had 3.31 ± 0.06 mg/mL of GABA content, 5.58 ± 0.52 mg gallic acid equivalent/mL of antioxidant activity, 234.68 ± 15.53 mg cyanidin-3-glucoside/mL of anthocyanin, an ability to inhibit growth of Bacillus cereus TISTR 687, Salmonella Typhi DMST 22842 and Shigella dysenteriae DMST 1511, and 10.54 ± 0.5 log₁₀ colony-forming units (CFU)/mL of viable L. brevis F064A cell count. This GABA-FMJ was considered as a potential naturally functional food for human of all ages.

Antimicrobial and Fermentation Potential of Himanthalia elongata in Food Applications

Himanthalia elongata is a brown oceanic seaweed rich in bioactive compounds. It could play an important role in food production because of its antimicrobial and antioxidant properties. Three strains belonging to the Lactobacillus casei group (Lactobacillus casei, Lactobacillus paracasei, and Lactobacillus rhamnosus) and a Bacillus subtilis strain were used for the solid-state fermentation of commercial seaweeds, and bacterial growth was monitored using the plate count method. High-pressure processing (HPP) was also employed (6000 bar, 5 min, 5 °C) before extraction. The antimicrobial activity of the extracts was tested in terms of the main food pathogenic bacteria (Salmonella spp., Listeria monocytogenes, Escherichia coli, Staphylococcus aureus, and Bacillus cereus), and the phenolic content was estimated using the Folin-Ciocalteau method. In addition, targeted UHPLC-MS² methods were used to unravel the profile of phlorotannins. H. elongata allowed the growth of the L. casei group strains and B. subtilis, showing the fermentability of this substrate. Significant antimicrobial activity toward L. monocytogenes was observed in the extracts obtained from unfermented samples, but neither fermentation nor HPP enhanced the natural antimicrobial activity of this seaweed species. The content in the phenolic compounds decreased because of the fermentation process, and the amount of phenolics in both the unfermented and fermented H. elongata extracts was very low. Despite phlorotannins being related to the natural antimicrobial activity of this brown seaweed, these results did not support this association. Even if fermentation and HPP were not proven to be effective tools for enhancing the useful compounds of H. elongata, the seaweed was shown to be a suitable substrate for L. casei group strains as well as for B. subtilis growth, and its extracts exhibited antimicrobial activity toward foodborne pathogens.

Comparative Susceptibility Study Against Pathogens Using Fermented Cranberry Juice and Antibiotics

In the present study, unfermented and fermented cranberry juice in combination with the Antibiotics vancomycin and tigecycline were tested for their antimicrobial activity. Cranberry juice was fermented with a recently isolated potentially probiotic Lactobacillus paracasei K5. The tested strains selected for this purpose were Enterococcus faecalis, E. faecium, Enterobacter cloacae and Staphylococcus aureus. The methods followed were the determination of zones inhibition, Minimum Inhibitory Concentration (MIC) and Fractional Inhibitory Concentration Index (FICI). Tigecycline together with fermented juice exhibited larger Zones of Inhibition (ZOI) in strains of E. faecium (65 ± 4.8 mm) compared to the respective ZOI with tigecycline and unfermented juice (no zone). The same outcome was also obtained with E. cloacae. Vancomycin together with fermented juice exhibited larger ZOI in strains of E. faecium (28 ± 2.2 mm) compared to the respective ZOI with vancomycin and unfermented juice (24 ± 2.3 mm). The lowest MIC values were recorded when tigecycline was combined with fermented cranberry juice against S. aureus strains, followed by the same combination of juice and antibiotic against E. cloacae strains. FICI revealed synergistic effects between fermented juice and tigecycline against a strain of E. faecium (A2020) and a strain of E. faecalis (A1940). Such effects were also observed in the case of fermented juice in combination with vancomycin against a strain of S. aureus (S18), as well as between fermented juice and tigecycline against E. cloacae (E1005 and E1007) strains. The results indicate that the antibacterial activity of juice fermented with the potentially probiotic L. paracasei K5 may be due to synergistic effects between some end fermentation products and the antibiotic agents examined.

Regulatory efficacy of fermented plant extract on the intestinal microflora and lipid profile in mildly hypercholesterolemic individuals

In recent years, the use of fermented plant products to protect against various metabolic syndromes has been increasing enormously. The objective of this study was to check the regulatory efficacy of fermented plant extract (FPE) on intestinal microflora, lipid profile, and antioxidant status in mildly hypercholesterolemic volunteers. Forty-four mildly hypercholesterolemic individuals (cholesterol 180–220 mg/dL) were recruited and assigned to two groups: experimental or placebo. Volunteers were requested to drink either 60 mL of FPE or placebo for 8 weeks. Anthropometric measurements were done in the initial, 4^th, 8^th, and 10^th weeks. The anthropometric parameters such as body weight, body fat, and body mass index were markedly lowered (p < 0.05) on FPE intervention participants. Moreover, the total antioxidant capacity and total phenolics in plasma were considerably increased along with a reduction (p < 0.05) in total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-c) after FPE supplementation. Participants who drank FPE showed a pronounced increase (p < 0.05) in the number of beneficial bacteria such as Bifidobacterium spp. and Lactobacillus spp., whereas the number of harmful bacteria such as Escherichia coli and Clostridium perfringens (p < 0.05) were concomitantly reduced. Furthermore, the lag time of LDL oxidation was substantially ameliorated in FPE-administered group, thus indicating its antioxidative and cardioprotective properties. Treatment with FPE substantially improved the intestinal microflora and thereby positively regulated various physiological functions by lowering the anthropometric parameters, TC, and LDL-c, and remarkably elevated the antioxidant capacity and lag time of LDL oxidation. Therefore, we recommended FPE beverage for combating hypercholesterolemia.

Effects of probiotic fermentation on the enhancement of biological and pharmacological activities of Codonopsis lanceolata extracted by high pressure treatment

This study was designed to evaluate the enhancement of antioxidant, antimicrobial, enzymatic, cytotoxic, and cognitive activities of Codonopsis lanceolata extracted by high pressure treatment followed by probiotic fermentation. Dried C. lanceolata samples were subjected to 400 MPa for 20 min and then fermented with Bifidobacterium longum B6 (HPE-BLF) and Lactobacillus rhamnosus (HPE-LRF) at 37 °C for 7 days. Compared to conventional extraction (CE-NF, 6.69 mg GAE/g), the phenol amounts of HPE-BLF and HPE-LRF were significantly increased to more than 8 mg GAE/g, while the lowest flavonoid contents were observed for HPE-BLF (0.44 mg RE/mL) and HPE-LRF (0.45 mg RE/mL) (p<0.05). Cinnamic acid was the most abundant phenolic acid in the fermented C. lanceolata. The highest DPPH scavenging activities were observed for HPE-BLF and HPE-LRF, with minimum EC(50) values of 1.26 and 1.18 mg/mL, respectively. The HPE-BLF and HPE-LRF samples exhibited the most noticeable antimicrobial activities against Staphylococcus aureus, Listeria monocytogenes, Salmonella Typhimurium, and Shigella boydii (MICs<15 mg/mL). The fermented C. lanceolata samples effectively inhibited α-glucosidase and tyrosinase activities and potentially improved a scopolamine-induced memory deficit in mice. The application of a fermentation process can effectively improve the biological and pharmacological activities of high-pressure-extracted C. lanceolata by increasing the extraction efficacy and inducing probiotic conversion. The results suggest that the combined treatment of HPE and a fermentation process could be used as alternative extraction method over CE.